Open access

Performances of Enzymatic Glucose/O2 Biofuel Cells

Written By

Habrioux Aurélien, Servat Karine, Tingry Sophie and Kokoh Boniface

Submitted: 20 October 2010 Published: 01 August 2011

DOI: 10.5772/17447

From the Edited Volume

Biofuel's Engineering Process Technology

Edited by Marco Aurélio dos Santos Bernardes

Chapter metrics overview

4,093 Chapter Downloads

View Full Metrics

1. Introduction

Nowadays, the development of stable devices capable of converting chemical energy into electrical one both to supply implantable devices and microelectronic apparatus is related in numerous papers (Bullen et al., 2006; Davis & Higson, 2007; Minteer et al., 2007). It is actually of great interest since it could be at the origin of new insight concerning the treatment of illness such as diabetes, deafness or heart disease (Heller, 2004; Katz & Willner, 2003). Besides it could also be a cheap solution to provide energy for microelectromechanical systems (Calabrese Barton et al., 2004) or to treat wastewater (Fishilevich et al., 2009). In the case where at least one of the catalyst used comes from biological resources (enzyme, microorganisms), these devices are called “biofuel cells”. As any fuel cell, a biofuel cell consists of two separated, or not, electrodes, an anode and a cathode. The research topic concerning biofuel cells is very vast and can be divided in three subsections. The first one includes microbial fuel cells which are bio-electrochemical systems that drive a current intensity by mimicking bacterial interactions found in nature. The second one deals with enzymatic biofuel cells which use enzymes as catalysts. In this kind of device the specificity of enzymes leads to the non-separation of each compartment of the cell, allowing to minimize the size of the system (Heller, 2004). The last kind of biofuel cells deals with hybrid biofuel cells that result in the combination of an enzymatic catalyst with an abiotic one. In these applications, it is possible to vary the operating conditions of the cell (pH value, concentration of reactants) so as to increase the power density. This chapter will only be focused on the second and third kind of biofuel cells. For the latter devices, the ideal fuel is obviously glucose which is present in all organic tissues and the oxidant is dioxygen. Nowadays there is a need for improvement in what concerns both the lifetime (in the range of a few days) (Calabrese Barton et al., 2004) and the power density (classically lower than 1 mW cm-2) (Neto et al., 2010) of these apparatus. For this reason we describe herein both phenomena affecting stability and power density of biofuel cells and proposed solutions in terms of electrode assembly, catalysts used and design of the cells. Moreover, since the major way to increase enzymatic electrodes lifetime and efficiency is to improve the enzyme connection with the electrode surface, we will have a special look on the different immobilization techniques presently reported in literature. Besides, in the past few years it has noticeably been demonstrated that abiotic catalysts obviously increased the stability of the device (Kerzenmacher et al., 2008) and involved fast substrate conversion kinetic characteristics (Choi et al., 2009). Consequently, we will have a particular glance on new abiotic nanocatalysts and their use in hybrid biofuel cells.

Advertisement

2. Enzymatic electrodes for glucose/O2 biofuel cells

Except the lack of stability of enzyme molecules due to their proteic nature, one of the major problems encountered with enzymatic electrodes concerns electron transfer between the enzyme and the electrode surface. In the next part we will describe the different electron transfer mechanisms occurring between an enzyme and the electrode as well as the immobilization techniques of the protein.

2.1. Electron transfer between enzyme and electrode

Enzymes are proteins which have high molecular weights. The active sites of these molecules are located in the organic matrix at a depth of several angstroms from the surface. It is thus easy to understand that kinetically fast electron transfer between enzymes and electrodes surface is difficult to obtain because of great insulation of the active centers (Armstrong et al., 1985). Different strategies have been used by the past to make efficient electrical connections between the enzyme and the electrode surface. Corresponding electron transfer mechanisms can be arranged in two different classes: mediated electron transfer (MET) and direct electron transfer (DET).

The major interest in directly transferring electrons between enzymes and electrodes is to reduce the electrode overpotential which is of particular importance for biofuel cells applications. DET is possible as soon as the distance between the active center of the enzyme and the electrode surface is in the order of a tunneling one (Degani & Heller, 1987). Different evidences for DET between enzymes classically used in glucose/O2 biofuel cells and electrodes have already been given. Actually, laccase (Gupta et al., 2004), bilirubin oxidase (Shleev et al., 2005) and glucose oxidase (Wang et al., 2009) are capable of exhibiting non-negligible catalytic current densities without the presence of a redox mediator.

In the case of MET, a redox molecule acts as a substrate and is able to transfer electrons between the electrode surface and the active center of the enzymatic molecule. Let’s notice that current densities obtained with MET are generally higher that what can be delivered in the case of DET. However, to get efficient MET, the redox mediator must possess some properties which can be deduced from Marcus theory as it was already mentioned by Rusling et al. (Rusling et al., 2008). This theory is used to describe outer sphere electron transfer between an electron donor (D) and an electron acceptor (A) as depicted in Fig. 1.

Figure 1.

Curves presenting potential energy of reactants (R) and products (P) (Aδ--Dδ+) as a function of reaction coordinates (RC).

The rate (k) of electron transfer can be described as follows (Eq.1.) by an Arrhenius type law.

where A is the collision frequency, K is the electronic transmission factor, ΔG 0 is the Gibbs free energy, R is the gas constant and T the temperature. λ is the reorganization energy (energetic cost associated to the reorganization of both solvent and molecules and necessary to proceed in electronic transfer between the donor and the acceptor). From this relation it can be deduced that to have an efficient electron transfer between enzyme and mediator, it is essential that the redox mediator used presents a highly reversible redox system to minimize λ value. It is also fundamental to minimize the ΔG 0 value. Thus it is very important that formal potentials of mediator and enzyme are close. Moreover, since active centers of enzyme are greatly insulated in high molecular weight molecules it is necessary to use small mediator molecules to reduce the distance of electron transfer and to guarantee a high k value.

2.2. Immobilization of enzymes on electrode surfaces

It is of great interest to develop new non-damaging immobilization techniques of enzyme for the development of stable biofuel cells. In fact, it is very difficult to propose a technique that does not affect the stability of biomolecules. Enzymes are proteins which possess tridimensional structures in which active centers are insulated. To keep the stability of the molecule and to preserve its catalytic efficiency it is necessary not to modify this tridimensional structure and particularly not to affect the environment of the active center. Different combining techniques can be used to immobilize enzymes onto the surface of solid electrodes:

  • immobilization into a polymer network

  • adsorption on an electrode material

  • covalent grafting to an electrode

  • immobilization within a membrane.

The first technique consists in immobilizing enzyme in an electropolymerized thin film. It is a very simple technique since it only needs to dip the electrode into a solution containing both monomers and biomolecules. Then the growth of polymer film can be realized by different ways: chronoamperometry (Brunel et al., 2007), chronopotentiometry or cyclic voltammetry (Fei et al., 2007). Different monomers such as pyrrole (Habrioux et al., 2008), aniline (Timur et al., 2004) or phenol (Bartlett et al., 1992) can be electropolymerized. This kind of films can be either conductive or not. The main advantage in using tridimensional conductive films lies in their ability to transfer electrons. Moreover, to increase the number of enzymatic molecules immobilized close to the electrode surface, a first adsorption step of enzymatic molecules can be performed (Merle et al., 2009). Other non-electropolymerized films can be used for enzyme holding. Currently, both chitosan and Nafion® are commonly used (Habrioux et al., 2010; Klotzbach et al., 2008). These two polymers possess surfactant properties interesting to immobilize enzymes in micellar structures (Moore et al., 2004). Moreover, the hydrophobic/hydrophilic property of the polymers can be tuned by modifying the chemical structure of these molecules (Klotzbach et al., 2008; Thomas et al., 2003). It is also possible to simply use retention properties of the Nafion® film for buffering its sulfonic groups (Habrioux et al., 2010). The main problem associated with the use of these polymers lies in the non-control of the film thickness. One of the most promising immobilization techniques has been proposed by Heller’s group. This approach consists in immobilizing enzymes in an osmium-based redox polymer (Mao et al., 2003) which is able to swell in contact with water. It acts both as an immobilizing network and an electrochemical mediator. The whole structure of the film leads to very fast electron transfer between the active centers of enzymes and the electrode surface. Another smart technique consists in covalent grafting of enzyme to the electrode surface. Thus Merle et al. (Merle et al., 2008) realized the grafting of amino groups on a carbon electrode before coupling these functions with amino-groups of enzymes using glutaraldehyde. This seems to confer a remarkable stability to the resulting electrode. Another well-known approach has been proposed by Willner et al. (Willner et al., 1996) that consisted in the reconstitution of the enzyme after the grafting of its active center on a gold electrode.

2.3. Enzymatic oxidation of glucose

The development of efficient enzymatic electrodes to oxidize glucose is of relevance for the development of implantable glucose/O2 biofuel cells. Nowadays, enzymes classically used to perform efficient oxidation of glucose to gluconic acid are either glucose oxidase (GOD) or glucose dehydrogenase (GDH). In the next part the properties of these two enzymes will be explained in details.

2.3.1. Glucose oxidation catalyzed by glucose dehydrogenase

Contrary to GOD, GDH is non-sensitive towards oxygen (Zhang et al., 2007). This is an attractive property for its use in glucose oxygen biofuel cells. However, GDH is an NAD-dependant enzyme. It is well-known that the oxidation of glucose catalyzed by GDH is rather limited by oxidation kinetics of NADH into NAD+. Even if the use of modified electrodes allows to reduce the overpotential associated to the oxidation of NADH into NAD+ (Delecouls-Servat et al., 2001), the stability of the electrodes remains poor. Another solution based on the use of a pyrroloquinoline quinone (PQQ) cofactor proposes to suppress the NAD dependence. Nevertheless, the PQQ cofactor has a limited stability (Wang, 2007).

2.3.2. Glucose oxidation catalyzed by glucose oxidase

Properties of the enzyme

GOD is by far the most used anode catalyst in glucose/O2 biofuel cells. Its molecular weight (155 kDa) and molecular size (60 Å × 52 Å × 77 Å) are high (Alvarez-Icaza et al., 1995). This constitutes a limitation for current densities obtained with a solid electrode since the footprint of the enzyme is great. This enzyme possesses two identical linked FAD (Flavine Adenine Dinucleotide) subunits which are responsible for β-D-glucose oxidation (Zhu et al., 2006) to gluconic acid (two electrons reaction product). The redox potential of FAD-FADH2 cofactor is ca. -0.36 V vs. Ag/AgCl/KCl(sat.) at a pH value of 7.2 (Stankovich et al., 1978), which is of particular interest for biofuel cells applications since it allows low-potential glucose oxidation. In this reaction, dioxygen is the natural electrons acceptor. Therefore, during the oxidation process, dioxygen is reduced towards hydrogen peroxide. The formation of H2O2 leads to inhibition of the enzyme because it modifies the amino groups in the vicinity of the active center (Kleppe, 1966). The pH value and the temperature have also an effect on GOD performances. Temperatures higher than 40 °C lead to a drastic decrease of activity (Kenausis et al., 1997). The pH value which optimizes GOD activity greatly depends on the electron acceptor. This value is equal to 5.5 and 7.5 when oxygen (Kenausis et al., 1997) methylene blue (Wilson & Turner, 1992) are used, respectively.

Performances of GOD electrodes towards β-D-glucose oxidation

In the case of MET, the use of suitable electrochemical mediators is of importance to increase the rate of electron transfer between the enzyme and the electrode surface since it allows to raise current densities. The second interest lies in the possibility to inhibit the formation of peroxide. Actually, it is just necessary to use a mediator which is able to realize faster electron transfer with GOD than oxygen can do. One of the most efficient systems has been developed by Heller’s group (Mano et al., 2005; Mao et al., 2003). It consists of a tridimensional matrix of an osmium based redox polymer containing GOD. The formal potential of the polymer is -195 mV vs. Ag/AgCl at pH 7.2. The covalent chain composed of thirteen atoms long allows the increase of the electron diffusion coefficient (Mao et al., 2003) by increasing the collision probability between reduced and oxidized forms of the osmium centers. The reticulation with PEGDGE (polyethyleneglycoldiglycydilether) allows the formation of a redox hydrogel capable of swelling in contact with water. It is probable that the matrix structure is responsible for a weak deformation of the protein structure. Such electrodes are able to deliver a catalytic current at potentials as low as -360 mV vs. Ag/AgCl in a physiologic medium containing 15 mM glucose (Mano et al., 2004).

2.4. Enzymatic reduction of oxygen to water

Generally, enzymes used to catalyze the reduction of oxygen into water are either laccase or bilirubin oxidase (BOD). The main property of these enzymes is their ability to directly reduce oxygen to water at potentials higher than what can be observed with platinum based electrodes (Soukharev et al., 2004). These two enzymes are classified in “multicopper oxidases” class and contain four Cu2+/Cu+ active centers which are commonly categorized in three types: T1, T2 and T3. T1 site is responsible for the oxidation of the electron donor. The trinuclear center composed both of T2 center and two equivalent T3 centers is the place where oxygen reduction occurs (Palmer et al., 2001). The associated mechanism is proposed in Fig. 2.

Figure 2.

Oxygen reduction catalyzed by “multicopper oxidases”

In the next part the different properties and performances of both laccase and BOD electrodes will be discussed.

2.4.1. Reduction of oxygen catalyzed by laccase

Laccase is able to oxidize phenolic compounds and to simultaneously reduce oxygen into water. The microorganism from which it is extracted greatly determines the redox potential of the T1 site which can vary from 430 mV vs. NHE up to 780 mV vs. NHE (Palmore & Kim, 1999). Laccase from Trametes versicolor is the most attractive one since redox potential of its T1 site is ca. 780 mV vs. NHE (Shleev et al., 2005). Nowadays, the best performances with laccase electrodes are obtained with osmium based polymers as redox mediators (Mano et al., 2006). Actually these electrodes are able to deliver a current density of 860 µA cm-2 at only -70 mV vs. O2/H2O at pH 5. In the same conditions, the identical current density is obtained at -400 mV vs. O2/H2O with a platinum wire as catalyst. Nevertheless, performances of laccase (from Pleurotus Ostreatus) electrodes drop drastically in the presence of chloride ions (Barton et al., 2002) what constitutes both a major problem and a great challenge for its use in implantable glucose/O2 biofuel cells.

2.4.2. Reduction of oxygen catalyzed by bilirubin oxidase

BOD is naturally capable of catalyzing the oxidation of bilirubin into biliverdin and to simultaneously reduce dioxygen (Shimizu et al., 1999). BOD is very similar to laccase. Performances of BOD electrodes are greatly related to the amino-acids sequence around T1 site of the enzyme (Li et al., 2004). It is clearly reported that the most efficient BOD enzyme comes from Myrothecium verrucaria. Redox potential of its T1 site is included between 650 and 750 mV vs. NHE, and the enzyme is thermally stable up to 60 °C (Mano et al., 2002b). It is thus possible to use it at physiological temperature without denaturing the protein. To build efficient BOD electrodes intended in working at physiological pH value, it is judicious to use positively charged mediator molecules since the isoelectric point of BOD is close to pH = 4. Actually, during oxygen reduction reaction, the use of an osmium based redox polymer has lead to performances such as 880 µA cm-2 at 0.3 V vs. Ag/AgCl (physiological conditions) at a scan rate of 1 mV s-1 (Mano et al., 2002a). Additionally, the redox osmium based hydrogel conferred a very favorable environment to stabilize BOD since 95% of the initial activity of a BOD electrode can be preserved after three weeks storage (Mano et al., 2002a). This remarkable stability probably results in auspicious electrostatic interactions between the swelling matrix and the enzyme. Performances of BOD electrodes are furthermore unaffected in the presence of chloride ions. In fact BOD remains active for chloride concentrations lower than 1 M (Mano et al., 2002a). This property is of major interest for the development of implantable microscale glucose/O2 biofuel cells using BOD as cathode catalysts. The major encountered problem with BOD electrodes is the relative lack of stability of the enzyme in physiological serum. Cupric centers of BOD are indeed capable of binding with one urea oxidation product, oxidation reaction catalyzed by the enzyme (Kang et al., 2004). This phenomenon can nevertheless be limited by spreading a Nafion® film on the catalyst (Kang et al., 2004). It is moreover reported that chemically modified Nafion® is capable of constituting a favorable environment to stabilize BOD (Topcagic & Minteer, 2006). Consequently, it seems of interest to immobilize BOD in Nafion® films. A promising technique for the development of efficient BOD electrodes has already been reported in literature (Habrioux et al., 2010). It consists in firstly adsorbing BOD/ABTS2- (2,2-azinobis-3-ethylbenzothiazoline-5-sulfonic acid) complex on a carbon powder, Vulcan XC 72 R in order to increase both enzyme loading, the stability of the protein and the quality of the percolating network in the whole thickness of the polymer film. Actually, to realize the electrochemical reaction, a triple contact point (between the catalytic system, the electrolyte and the electronic conductor) is required. Once the catalytic system is adsorbed, a buffered Nafion® solution is added. The whole system is then immobilized onto a solid carbon electrode (Fig. 3).

Figure 3.

Method used for the preparation of BOD cathodes according to the process described in Ref. (Habrioux et al., 2010)

Previous studies have shown the interest lying in the use of ABTS2- as redox mediator in combination with multicopper oxidases. One of them was carried out by Karnicka et al. who have shown that wiring laccase to glassy carbon through a ABTS2-/carbon nanotube system was a very efficient pathway to reduce molecular oxygen into water (Karnicka et al., 2008). The combination of ABTS2- with BOD is also known to exhibit a high electrochemical activity towards oxygen reduction reaction (Tsujimura et al., 2001). These observations are confirmed by electrochemical studies performed on electrodes previously described (Fig. 3). Results are shown in Fig. 4.

Figure 4.

Oxygen reduction reaction catalyzed by BOD/ABTS2-/Nafion® electrode in a phosphate buffered solution (pH = 7.4, 0.2 M) at 25 °C. Curves registered at different rotation rates (Ω), in an air-saturated electrolyte at Ω = 100 rpm (■); Ω = 200 rpm (●); Ω = 400 rpm (Δ); Ω = 600 rpm (□) and in an oxygen saturated electrolyte at Ω = 600 rpm (○). Scan rate 3 mV s-1.

Curves of Fig.4 clearly show the interest of such electrodes that exhibit a catalytic current from potentials as high as -50 mV vs. O2/H2O (0.536 V vs. SCE). Furthermore the half-wave potential is only 100 mV lower than the reversible redox potential of O2/H2O. This value is in good agreement with that reported by Tsujimura et al. (0.49 V vs. Ag/AgCl/KCl(sat.) at pH = 7.0) (Tsujimura et al., 2001). Let’s notice that the half-wave potential value is very close to the redox potential of T1 site of BOD (0.46 V vs. SCE). This has already been explained by the fact that the reaction between ABTS2- and BOD is an uphill one (Tsujimura et al., 2001). Fig. 4 also shows that electrochemical performances of BOD/ABTS2-/Nafion® clearly depend on the amount of oxygen dissolved in the electrolyte. The limiting current is a plateau and increases from 0.56 mA cm-2 in an air saturated electrolyte to 1.61 mA cm-2 in an oxygen saturated (at a rotation rate of 600 rpm). Dependence of limiting current with oxygen concentration in the electrolyte is presented in Fig.5. In this figure, current obtained at 0.2 V vs. SCE is plotted versus oxygen saturation.

Figure 5.

Electrochemical activity of BOD/ABTS2-/Nafion® electrode: dependence of the current value at 0.2 V vs. SCE with oxygen concentration

The current linearly increases with the oxygen concentration from low values to around 35%. This linearity suggests that the reaction is of a first order with oxygen concentration thereby, the Koutecky–Levich plots can be considered. Assuming that the rate determining step is an enzymatic intramolecular electron transfer step, it is possible to express the current density of a BOD/ABTS2-/Nafion® electrode working in an air saturated solution as follows (Schmidt et al., 1999):

In Eq.2, j L diff represents the diffusion limiting current density expressed by Levich equation:

In Eq.3, n is the number of electrons exchanged, D the diffusion coefficient, C 0 is the oxygen concentration, Ω is the rotation rate, F the Faraday constant and ν is the kinematic viscosity. Then, j L film corresponds to the limitation due to oxygen diffusion in the catalytic film and j L ads is the limiting current density due to oxygen adsorption on the catalytic site. Since these two last contributions to the total current density do not depend on Ω, it is impossible to separate them. They will be described according to Eq.4.

In Eq.2, η is the overpotential (η = E−E eq ), j 0 the exchange current density, α the transfer coefficient, R = 8.31 J mol−1 K−1, F=96500 C mol−1 and T the temperature. Ө and Ө c are the covering rates of the active sites of the enzyme at E and E eq , respectively. We will assume that ӨӨ c for all potential values. From Eq.2, when Ω→∞, the limit of 1/j can be expressed as follows:

In Eq.5, when η→∞, 1/j k1/j L. It is thus possible to determine j L value by extrapolating and reporting the 1/j k values as a function of the potential value E. Transforming Eq.5 (Grolleau et al., 2008), it becomes as follows:

where b = RT/αnF is the Tafel slope. The plot of the η values vs. ln(j K /(j L −j K )) (Fig. 6) permits the calculation of b and j 0 values.

Figure 6.

Curve obtained from Koutecky-Levich treatment on oxygen reduction reaction catalyzed by BOD/ABTS2-/Nafion® system.

Under these experimental conditions, calculated values for both Tafel slope and exchange current density are respectively of 69 mV/decade and 25 µA cm-2. The high value obtained for j 0 confirms the ability of BOD/ABTS2-/Nafion® system to activate molecular oxygen in a physiological type medium. Moreover, it also certifies that the oxygen reduction reaction starts at very high potentials. The reference catalyst classically used to reduce molecular oxygen is platinum. It can be noticed that under similar conditions, the exchange current density is only of 5 µA cm-2 when we used platinum nanoparticles as catalyst. This clearly shows the great interest lying in these electrodes to reduce oxygen in glucose/O2 biofuel cells. Nowadays, the major problem encountered with these electrodes is the lack of stability of the redox mediator (ABTS2-) (Tsujimura et al., 2001).

Advertisement

3. Abiotic catalysts for glucose/O2 biofuel cells

In this part, a complete description of non-enzymatic catalysts which are used or potentially usable in glucose/O2 biofuel cells systems is given. The major problem in employing abiotic catalyst in such applications lies in their lack of specificity. Consequently, their application in implantable microscale devices is difficult. Nevertheless, they often lead to fast substrate conversion kinetic characteristics and their stability is incomparably higher than enzymes one. Thus, they can be used as catalysts in biocompatible devices intended in supplying long-term high power densities.

3.1. Non-enzymatic oxidation of glucose

3.1.1. Different offered possibilities

A promising approach consists in using metallophtalocyanines to realize glucose oxidation. Particularly, cobalt phtalocyanines seem to exhibit interesting properties (Zagal et al., 2010). Furthermore, reactivity of these electrodes can be modulated by simple modification of the complex structure what is of interest for the development of electrodes. These catalysts could be used for glucose electrooxidation in glucose/O2 biofuel cells but it is not still developed.

The other approach lies in the use of metallic nanomaterials as catalysts. Oxidation of glucose on metallic surfaces has extensively been studied. Among all these investigations, numerous ones have been devoted to the understanding of catalytic effect of platinum on glucose oxidation process (Kokoh et al., 1992a; Kokoh et al., 1992b; Sun et al., 2001). Experiments led to conclude that the major oxidation product is gluconic acid (Kokoh et al., 1992b; Rao & Drake, 1969). Actually, the oxidation process involves dehydrogenation of the anomeric carbon of glucose molecule (Ernst et al., 1979). The major interest in including platinum in the catalyst composition lies in its ability to oxidize glucose at very low potentials (lower than 0.3 V vs. RHE). However, it is also well-known that platinum surfaces are particularly sensitive to poisoning with chemisorbed intermediates (Bae et al., 1990; Bae et al., 1991). To solve this problem, different heavy atoms (Tl, Pb, Bi and W) have been used as adatoms to modify platinum surfaces to raise electrochemical activity of platinum (Park et al., 2006). Other studies relate glucose oxidation on platinum alloys in which the second metal can be Rh, Pd, Au, Pb (Sun et al., 2001), Bi, Ru and Sn (Becerik & Kadirgan, 2001). It appears that the most efficient catalysts are Pt-Pb or Pt-Bi (Becerik & Kadirgan, 2001). However, these catalysts are sensitive to dissolution of the second metal which prevents their use in fuel cells systems. Moreover most of the materials previously cited are toxic. The only one which could be environmentally friendly is gold even if the oxidative stress caused by nanoparticles on living cells is not well-known. Besides, synthesis of alloyed materials allows increasing significantly catalytic activity of pure metals by synergistic effect. This has noticeably been observed with platinum-gold nanoalloys (Möller & Pistorius, 2004).

3.1.2. Oxidation of glucose on gold-platinum nanoparticles

The oxidation of glucose on gold-platinum nanoparticles has been investigated in numerous studies (Habrioux et al., 2007; Sun et al., 2001). Jin and Chen (Jin & Chen, 2007) examined glucose oxidation catalyzed by Pt-Au prepared by a co-reduction of metallic salts. An oxidation peak of glucose was visible at much lower potentials than on gold electrode. Moreover, they showed that both metals favored the dehydrogenation of the glucose molecule. They concluded that the presence of gold prevents platinum from chemisorbed poisonous species. The efficiency of such catalysts towards glucose oxidation is thus not to be any more demonstrated, and greatly depends on the synthesis method used to elaborate the catalytic material.

Synthesis of gold-platinum nanoparticles

Various gold-platinum nanoparticles synthesis methods have been already studied: Polyol (Senthil Kumar & Phani, 2009), sol-gel (Devarajan et al., 2005), water-in-oil microemulsion (Habrioux et al., 2007), electrodeposition (El Roustom et al., 2007) and Bönnemann (Atwan et al., 2006). Among all these methods, the water-in-oil microemulsion technique produces particles that exhibit high catalytic activity towards glucose electrooxidation (Habrioux et al., 2007). It consists in mixing two microemulsions, one containing the reducing agent in the aqueous phase and the other containing one or several metallic precursors in the aqueous phase. Collisions of water nanodroplets permit to obtain metallic nanoparticles which can be then cleaned and dispersed onto a carbon support. The choice of the different components of the microemulsions is not unique and influences the physical properties of the obtained nanoparticles. Actually, both surfactant molecules and oil-phase chemical nature have an effect on interfacial tension of the surfactant film that determines water solubility in micelles (Paul & Mitra, 2005). This greatly affects intermicellar exchanges. Moreover, the chemical nature of the reducing agent controls the rate of the nucleation step and subsequently the kinetic of particles formation. In the system described herein, n-heptan is used as oil phase, non-ionic polyethyleneglycol-dodecylether as emulsifier molecule and sodium borohydride as reducing agent. The synthesized particles have been dispersed onto Vulcan XC 72 R and then washed several times with acetone, ethanol and water, respectively to remove surfactant from their surface (Habrioux et al., 2009b). The removal of surfactant molecules from all the catalytic sites without modifying structural properties of the catalyst is currently a great challenge (Brimaud et al., 2007). Since electrocatalysis is a surface phenomenon depending on the chemical nature of the surface of the catalyst, on its crystalline structure and on the number of active sites, it is useful to precisely know the physico-chemical properties of the used nanoparticles to understand their electrochemical performances.

Electrochemical behaviour of gold-platinum nanoparticles towards glucose electrooxidation

This part aims at showing the importance to realize a correlation between the structural properties of the catalysts and their electrocatalytic activities towards glucose oxidation. The use of nanocatalysts indeed involves a deep structural characterization of the nanoparticles to fully understand the whole of the catalytic process. Therefore, in order to show the presence and the proportion of gold and platinum at the surface of the catalysts, electrochemical investigations have been carried out (Burke et al., 2003). It is indeed possible to quantify surface compositions of the catalysts by using cyclic voltammetry and by calculating the amount of charge associated with both reduction of platinum and gold oxides (Woods, 1971). The charge calculated for pure metals was 493 μC cm-2 and 543 μC cm-2 for Au and Pt, respectively, for an upper potential value of 250 mV vs. MSE (Habrioux et al., 2007) in a NaOH (0.1 M) solution. The atomic ratio between gold and platinum can be thus determined according to Eq. 7 and Eq. 8 assuming that for all bimetallic compositions, the oxidation takes place only on the first atomic monolayer.

and

Both voltammograms used and results of the quantification are shown in Fig. 7. Mean diameter of the different nanoparticles weighted to their volume (obtained from transmission electron microscopy measurements) as well as their mean coherent domain size weighted to the volume of the particles (obtained from X-ray diffraction measurements) are also presented in Fig. 7.

Figure 7.

Voltammograms (after 19 cycles) of gold-platinum nanoparticles recorded at 25 °C in alkaline media (0.1 M NaOH). Scan rate = 20 mV s-1. The surface composition of the used catalyst is given on the right of the corresponding voltammogram.

In Fig. 7 it is noticed that for all compositions, desorption of oxygen species occurs in two peaks. The reduction of the gold surface takes place at -0.38 V vs. MSE whereas the potential for which platinum surface is reduced depends on the amount of gold in the alloy. Indeed, for pure platinum nanoparticles this potential is ca. -0.8 V vs. MSE (reduction of platinum oxides). The potential at which oxygen species desorption occurs, shifts to lower potentials when the atomic ratio of gold increases in the composition of alloys. The deformation of this peak increases with the amount of gold probably because of the formation of more complex platinum oxides. The quantification realized on the different bimetallic compositions, clearly shows a platinum enrichment of nanoparticles surfaces. Desorption of gold oxides is indeed invisible for low gold containing samples (i.e. with gold content lower than 40%). These nanoparticles exhibit a typical core-shell structure composed of a gold core and a platinum shell (Habrioux et al., 2009b), while high gold content samples (i.e. with gold content higher than 80%) possess a surface composition that is close to the nominal one. This results in a purely kinetic effect. Actually, reduction of gold precursor is considerably faster than reduction of platinum cation. Consequently, there is firstly formation of a gold seed on which platinum reduction occurs. So, the natural tendency of these systems is to form core-shell particles. Furthermore, let’s notice that both mean diameter of nanoparticles weighted to their volume and their mean coherent domain size weighted to their volume increase with gold content but ever stay in the nanometer range. That is only the result of differences in reduction kinetics of the particles since the ratio water to surfactant remains constant whatever the synthesized sample. To correlate surface composition with efficiency to oxidize glucose for all gold-platinum catalysts compositions, voltammograms were first recorded in alkaline medium. Results are shown in Fig. 8.

Figure 8.

Voltammograms (after 19 cycles) of gold-platinum nanoparticles recorded at 3 °C in alkaline medium (0.1 M NaOH) in the presence of 10 mM glucose. Scan rate = 20 mV s-1. Surface composition of the used catalyst is given on the right of the corresponding voltammogram.

In Fig. 8, different oxidation peaks appear during the oxidation process on gold-platinum nanocatalysts. When platinum content decreases in the bimetallic surface composition, intensity of peak A, located at ca. -0.7 V vs. SCE, diminishes. For pure gold catalyst, this peak is furthermore invisible. It is thus related to the oxidation phenomenon on platinum. It has already been attributed to dehydrogenation of anomeric carbon of glucose molecule (Ernst et al., 1979). Peaks B and C correspond to the direct oxidation of glucose molecule (Habrioux et al., 2007) and are located both in gold and platinum oxides region. In the case of catalysts with nominal compositions such as Au70Pt30 or Au80Pt20, the different oxidation peaks located between -0.3 V vs. SCE and 0.4 V vs. SCE are not well-defined. For these catalysts, the presence of platinum at their surface allows a low potential oxidation of glucose molecule, which starts earlier than on pure gold. Moreover, on these catalysts, after the dehydrogenation step, current densities raise rapidly. Furthermore, in the potential region where formation of both gold hydroxides and platinum oxides occurs, current densities are very high (i.e. 12 mA mg-1 at 0.2 V vs. SCE). This is the result of a synergistic effect between the two oxidized metals at the bimetallic catalyst surface (Habrioux et al., 2007). Such effect between gold and platinum has already been observed for CO oxidation (Mott et al., 2007). On these catalysts, during the negative going scan, two oxidation peaks, E and F, are visible.

During the reduction of both oxidized gold and platinum clusters, oxygenated species are desorbed from the surface and stay at its vicinity. Subsequently, there is desorption of adsorbed lactone from the electrode surface what implies the formation of both peak E and peak F (Beden et al., 1996). Fig. 9 shows the reactions involving in the oxidation of glucose on the catalyst surface.

Figure 9.

Oxidation of glucose on gold-platinum catalysts

The remarkable electrocatalytic activity of both Au80Pt20 and Au70Pt30 nanocatalysts towards glucose electrooxidation is probably the result of a suitable surface composition combined with a convenient crystallographic structure. An X-ray diffraction study (Fig. 10) based on Warren’s treatment of defective metals and previously described (Vogel et al., 1998; Vogel et al., 1983) combined with high resolution transmission electron microscopy (HRTEM) measurements allowed to exhibit the peculiar structure of high gold content catalysts (Habrioux et al., 2009b).

Figure 10.

a) Experimental and simulated diffractograms obtained with Au, Au70Pt30 and Pt nanoparticles (from top to bottom), b) Experimental (●) and simulated (○) Williamson-Hall diagrams obtained with Au30Pt70 and Au nanoparticles (from top to bottom).

Each experimental diffractogram has been fitted with five Pearson VII functions what gives two important parameters: the accurate peak position b (b = 2sin𝛉/λ) and the integral line width db. The value of db is plotted versus b in Fig.10b. As a result of best fits, it can be assumed that line profiles of diffractograms are lorentzian. This implies that all contributions to the integral line width can be added linearly and can be expressed as follows:

with

and

where L v is the mean coherent domain size weighted to the volume of the particles, α the stacking fault probability, V hkl a parameter depending on the miller indexes, σ the mean internal stress and E hkl the young modulus. The fit of Williamson-Hall diagrams with the expression given by Eq.7 leads to the determination of L v , α and σ for each catalyst. It has been concluded that for catalysts with nominal compositions of Au70Pt30 and Au80Pt20, both σ and α values were high (Habrioux et al., 2009b). For Au80Pt20, these values were indeed of 510 N.mm-2 and 8.2%, respectively for σ and α. In the case of Au70Pt30, these values were of 490 N.mm-2 and 7.4%. HRTEM observations have confirmed the results of the fit since the observed particles present numerous twins and stacking faults, as shown in Fig. 11.

Figure 11.

HRTEM observations of Au70Pt30 nanoparticle (left image) and Au nanoparticle (right image).

As a result of the high internal mean strain existing in these particles, there is an important strain energy which leads to the formation of twins and stacking faults. Consequently the equilibrium shape of the particles is modified and the interaction between the different surface atoms is changed. Accordingly, the catalytic behaviour of these particles is greatly affected. This can also explain the remarkable activity of these particles towards glucose oxidation both in alkaline medium as shown in Fig. 8, and in physiological type medium, as shown in Fig. 12.

Let’s notice that at low potential values, current densities obtained with Au70Pt30 and Pt catalysts are similar. Competitive adsorption between phosphate species and glucose molecules can be involved to explain this phenomenon. Actually, de Mele et al. (de Mele et al., 1982) showed that phosphate species are capable of creating oxygen-metal bonds with platinum surfaces and thus inhibiting glucose oxidation. This engenders the low current density observed at low potentials on pure platinum. On Au70Pt30 catalyst, it is possible that modification of 5d band center of platinum due to the presence of gold allows discriminating the adsorption of phosphate species. Furthermore, the oxidation of glucose on high gold content catalysts starts at a very low potential value (i.e. -0.5 V vs. SCE), which can easily be compared with values observed for catalysts such as Pt-Bi, Pt-Sn (Becerik & Kadirgan, 2001) or Pt-Pd (Becerik et al., 1999).

Figure 12.

Voltammograms (after 19 cycles) of gold-platinum nanoparticles recorded at 37 °C in a phosphate buffered solution (0.1 M pH 7.4) in the presence of 10 mM glucose. Scan rate = 20 mV s-1.

3.2. Oxygen reduction reaction on abiotic catalysts

It is difficult to tailor non-enzymatic catalyst, capable of exhibiting electrochemical performances similar to those shown by laccase or BOD in physiological type media. The major problem with enzymes lies in the natural lack of stability of the proteins. One of the possibilities to tailor new efficient and stable cathode catalysts for glucose/O2 biofuel cells is to artificially reproduce active centers of enzymes and to stabilize their environment by mimicking the structure of enzymatic proteins and by removing all organic parts responsible for instability of enzymes. The possibility of designing this kind of catalyst has already been discussed (Ma & Balbuena, 2007).

Advertisement

4. Design of glucose/O2 biofuel cells

The global reaction associated to the glucose/O2 biofuel cell can be described according to Eq. 13 :

Gibbs free energy associated to this reaction is Δ r G 0 = -251 kJ mol-1. This implies that the theoretical cell voltage is E 0 = 1.3 V (Kerzenmacher et al., 2008). Furthermore, when the cell delivers a current j, the cell voltage E(j) can be expressed as follows:

where η a is the anodic overvoltage, η c the cathodic one, R the cell resistance and E eq the equilibrium cell voltage. In Eq.14, it clearly appears that both values of η a, η c and R must be very low in order to increase the cell performances.

Since the development of the first biofuel cell realized by Yahiro et al. (Yahiro et al., 1964) that consisted in a two-compartment anionic membrane cell in which two platinum foils were used as conducting supports, numerous progress have been realized in designing devices. Nowadays, four main designs are developed. The first one has been developed by Heller’s group. It simply consists in using two carbon fibers of 7 µm diameter as electrode materials. On these fibers, enzymes are immobilized in a redox osmium based hydrogel capable of immobilizing enzymes. These two electrodes are directly dipped into the electrolyte. In a physiological medium containing 15 mM glucose, the device was primarily able to deliver a power density of 431 µW cm-2 at a cell voltage of 0.52 V (Mano et al., 2002c). The device exhibited a high stability, since after one week of continuous working, it was still capable of delivering 227 µW cm-2. Based on this study, and by replacing carbon fibers by newly engineered porous microwires comprised of assembled and oriented carbon nanotubes, Mano’s group (Gao et al., 2010) recently made the most efficient glucose/O2 biofuel cell ever designed. It indeed achieved a remarkably high power density of 740 µW cm-2 at a cell voltage of 0.57 V. The success of the experiment probably lies in the increase of the mass transfer of substrates. Other promising but presently less performing designs of glucose/O2 biofuel cells have been developed in the recent past years. The first one consists in using a microfluidic channel to build a glucose/O2 biofuel cell. The laminar flow obtained in the channel at low Reynold’s number prevents the electrodes from depolarization phenomena and/or from degradation. The mixing of the reactants indeed occurs only on a very small distance in the middle of the channel. The development of such glucose/O2 biofuel cells seems of great interest for various applications. It is very simple to use abiotic and non-specific materials as catalysts. Moreover, it offers the possibility of working with two different pH values for the catholyte and the anolyte what can be interesting to improve electrochemical performances of each electrode (Zebda et al., 2009a). Nowadays, these devices are capable of delivering 110 µW cm-2 for a cell voltage of 0.3 V (Zebda et al., 2009b) by using GOD and laccase as catalysts. Glucose/O2 biofuel cells realized with classical fuel cell stacks have also been carried out (Habrioux et al., 2010). Both the used system and the obtained performances are described in Fig. 13.

Figure 13.

a) Description of the glucose/O2 biofuel cell design, b) Characteristic E vs. j of glucose/O2 cell performed at 20 °C: anode (Au70Pt30/Vulcan XC 72R, metal loading 40%); cathode (BOD/ABTS/Vulcan XC 72 R system). Test realized in the presence of a phosphate buffered solution (0.2 M; pH 7.4) containing 0.3 M glucose. The cathodic compartment contains an oxygen saturated phosphate buffered solution (pH 7.4; 0.2 M).

Fig. 13 shows that the maximum power density obtained is 170 µW cm−2 for a cell voltage of 600 mV. However, let’s notice that performances of the biofuel cell rapidly decrease for current densities higher than 300 µA cm-2. This is clearly due to a very low ionic exchange rate between the two compartments of the cell since this value is too weak to correspond to mass transfer limitation of glucose molecule. The last design of glucose/O2 biofuel cell developed in the last past years is the concentric device (Habrioux et al., 2008; Habrioux et al., 2009a). It is based on concentric carbon tubes as electrodes and operates at physiological pH. An oxygen saturated solution circulates inside the internal tube composed of porous carbon, which is capable of providing oxygen diffusion. The whole system is immersed in a phosphate buffered solution (pH 7.4, 0.1 M) containing various glucose concentrations. Oxygen consumption occurs at the cathode such that no oxygen diffuses towards the anode. This allows to use in this device both abiotic and enzymatic materials as anode and cathode catalysts, respectively. BOD/ABTS/Vulcan XC 72 R system is immobilized on the internal surface of the inner tube whereas Au-Pt nanocatalysts are immobilized on the internal surface of the outer tube. The surfaces of the cathode and anode were 3.14 and 4.4 cm2, respectively. The system is fully described in Fig. 14.

Figure 14.

Schematic view of the glucose/O2 biofuel cell system

Different fuel cell tests realized by using various nominal compositions of Au-Pt nanomaterials have been realized. The best performances are obtained with Au70Pt30 as anodic catalyst. Actually, the maximum power density achieved is approximately of 90 µW cm-2 for a cell voltage of 0.45 V. Results are shown in Fig. 15.

Figure 15.

Fuel cell performances obtained with Au (▲), Au80Pt20 (■), Au70Pt30 (□) and Pt (Δ) nanoparticles as anode catalysts. These performances were obtained in a phosphate buffered solution (0.2 M, pH 7.4) containing 10 mM glucose at 37 °C. A saturated oxygen solution circulated in the inner tube of the device.

When Au80Pt20 is used as anode catalyst, the open circuit voltage is lower (i.e. 0.64 V). This is clearly explained by the surface composition of the catalyst which only contains 29 at.% of platinum. In the case of pure platinum, the open circuit voltage is very low due to strong competitions between phosphate species and glucose for adsorption. Such competition also occurs on other Au-Pt catalysts but the presence of gold allows a weaker interaction between phosphate species and the metallic surface. Consequently, higher glucose concentrations were used so as to improve biofuel cell performances. The obtained results are given in Fig. 16.

Figure 16.

Fuel cell performances obtained with 10 mM glucose (Δ), 100 mM glucose (●), 300 mM glucose (○) and 700 mM glucose (□), with Au70Pt30 nanoparticles as anode catalyst. Performances obtained in a phosphate buffered solution (0.2 M, pH 7.4) at 37 °C. A saturated O2 solution circulated in the inner tube.

The data show a strong increase in cell voltage with glucose concentration. The raise observed in cell voltage between 0.1 M and 0.3 M can be attributed to the slow adsorption of phosphate species due to the presence of a higher glucose concentration. The maximum power density was also increased from 90 µW cm-2 (for a glucose concentration of 10 mM) up to 190 µW cm-2 (for a glucose concentration of 0.7 M). Nevertheless, in all cases, the fuel cell performances are greatly limited by resistance of the cell.

Advertisement

5. Conclusion

In this chapter we clearly show the importance of both electrodes assembly and global design of the cell on power output of the glucose/O2 biofuel cell. Moreover, it seems that a suitable choice of well-characterized nanocatalysts materials can lead both to an increase of the cell performances and to an improvement of their lifetime resulting in the abiotic nature of these materials. The approach, which consists of the utilization of an abiotic anode catalyst and an enzyme for a four electrons reduction, can undoubtedly open new outlooks for biofuel cells applications. This hybrid biofuel cell combines the optimized fuel electrooxidation, as developed in classical fuel cells, with the complete reduction of dioxygen to H2O without H2O2 production. Moreover, a concentric membrane-less design associated with an appropriate immobilization of the catalysts can avoid a costly separator of the cell events. Nevertheless, progresses to develop an efficient cell design are still necessary.

References

  1. 1. Alvarez-Icaza M. Kalisz H. M. Hecht H. J. Aumann K. D. Schomburg D. Schmid R. D. 1995 The design of enzyme sensors based on the enzyme structure Biosensors and Bioelectronics 10 8 735 742 0956-5663
  2. 2. Armstrong F. A. Hill H. A. O. Walton N. J. 1985 Reactions of electron-transfer proteins at electrodes. Quartely Reviews of Biophysics, 18 03 261 322 0033-5835
  3. 3. Atwan M. H. Macdonald C. L. B. Northwood D. O. Gyenge E. L. 2006 Colloidal Au and Au-alloy catalysts for direct borohydride fuel cells: Electrocatalysis and fuel cell performance Journal of Power Sources 158 1 36 44 0378-7753
  4. 4. Bae I. T. Xing X. Liu C. C. Yeager E. 1990 In situ Fourier transform infrared reflection absorption spectroscopic studies of glucose oxidation on platinum in acid Journal of Electroanalytical Chemistryand Interfacial Electrochemistry, 284 2 335 349 0022-0728
  5. 5. Bae I. T. Yeager E. Xing X. Liu C. C. 1991 In situ infrared studies of glucose oxidation on platinum in an alkaline medium Journal of Electroanalytical Chemistryand Interfacial Electrochemistry, 309 1-2 131 145 0022-0728
  6. 6. Bartlett P. N. Tebbutt P. Tyrrell C. H. 1992 Electrochemical immobilization of enzymes. 3. Immobilization of glucose oxidase in thin films of electrochemically polymerized phenols Analytical Chemistry 64 2 138 142 0003-2700
  7. 7. Barton S. C. Pickard M. Vazquez-Duhalt R. Heller A. 2002Electroreduction of O2 to water at 0.6 V (SHE) at pH 7 on the "wired" Pleurotus ostreatus laccase cathode. Biosensors and Bioelectronics, 17 11-12 1071 1074 0956-5663
  8. 8. Becerik I. Kadirgan F. 2001 Glucose sensitivity of platinum-based alloys incorporated in polypyrrole films at neutral media Synthetic Metals 124 2-3 379 384 0379-6779
  9. 9. Becerik I. Süzer S. Kadirgan F. 1999 Platinum-palladium loaded polypyrrole film electrodes for the electrooxidation of d-glucose in neutral media Journal of Electroanalytical Chemistry 476 2 171 176 1572-6657
  10. 10. Beden B. Largeaud F. Kokoh K. B. Lamy C. 1996Fourier transform infrared reflectance spectroscopic investigation of the electrocatalytic oxidation of-glucose: Identification of reactive intermediates and reaction products. Electrochimica Acta, 41 5 701 709 0013-4686
  11. 11. Brimaud S. Coutanceau C. Garnier E. Léger J. M. Gérard F. Pronier S. Leoni M. 2007 Influence of surfactant removal by chemical or thermal methods on structure and electroactivity of Pt/C catalysts prepared by water-in-oil microemulsion Journal of Electroanalytical Chemistry 602 2 226 236 1572-6657
  12. 12. Brunel, L.; Denele, J.; Servat, K.; Kokoh, K.B.; Jolivalt, C.; Innocent, C.; Cretin, M.; Rolland, M. & Tingry, S. (2007). Oxygen transport through laccase biocathodes for a membrane-less glucose/O2 biofuel cell. Electrochemistry Communications, Vol. 9, No. 2, pp. 331-336, ISSN 1388-2481
  13. 13. Bullen, R.A.; Arnot, T.C.; Lakeman, J.B. & Walsh, F.C. (2006). Biofuel cells and their development. Biosensors and Bioelectronics, Vol. 21, No. 11, pp. 2015-2045, ISSN 0956-5663
  14. 14. Burke L. D. Moran J. Nugent P. 2003 Cyclic voltammetry responses of metastable gold electrodes in aqueous media Journal of Solid State Electrochemistry 7 9 529 538 1432-8488
  15. 15. Calabrese Barton. S. Gallaway J. Atanassov P. 2004 Enzymatic Biofuel Cells for Implantable and Microscale Devices Chemical Reviews 104 10 4867 4886 0009-2665
  16. 16. Choi Y. Wang G. Nayfeh M. H. Yau S. T. 2009 A hybrid biofuel cell based on electrooxidation of glucose using ultra-small silicon nanoparticles Biosensors and Bioelectronics 24 10 3103 3107 0956-5663
  17. 17. Davis F. Higson S. P. J. 2007 Biofuel cells--Recent advances and applications. Biosensors and Bioelectronics 22 7 1224 1235 0956-5663
  18. 18. de Mele, M.F.L.; Videla, H.A. & Arvia, A.J. (1982). Potentiodynamic Study of Glucose Electro-Oxidation at Bright Platinum Electrodes. Journal of The Electrochemical Society, Vol. 129, No. 10, pp. 2207-2213, ISSN 1945-7111
  19. 19. Degani Y. Heller A. 1987 Direct electrical communication between chemically modified enzymes and metal electrodes. I. Electron transfer from glucose oxidase to metal electrodes via electron relays, bound covalently to the enzyme The Journal of Physical Chemistry 91 6 1285 1289 0022-3654
  20. 20. Delecouls-Servat K. Bergel A. Basseguy R. 2001Surface-modified electrodes for NADH oxidation in oxidoreductase-catalyzed synthesis. Journal of applied electrochemistry, 10 31 1095 1101 1572-8838
  21. 21. Devarajan S. Bera P. Sampath S. 2005 Bimetallic nanoparticles: A single step synthesis, stabilization, and characterization of Au-Ag, Au-Pd, and Au-Pt in sol-gel derived silicates Journal of Colloid and Interface Science, 290 1 117 129 0021-9797
  22. 22. El Roustom B. Siné G. Fóti G. Comninellis C. 2007 A novel method for the preparation of bi-metallic (Pt-Au) nanoparticles on boron doped diamond (BDD) substrate: application to the oxygen reduction reaction Journal of applied electrochemistry 37 11 1227 1236 0002-1891X.
  23. 23. Ernst, S.; Heitbaum, J. & Hamann, C.H. (1979). The electrooxidation of glucose in phosphate buffer solutions : Part I. Reactivity and kinetics below 350 mV/RHE. Journal of Electroanalytical Chemistry, Vol. 100, No. 1-2, pp. 173-183, ISSN 0368-1874
  24. 24. Fei J. Song H. K. Palmore G. T. R. 2007 A biopolymer composite that catalyzes the reduction of oxygen to water Chemistry of Materials 19 7 1565 1570 0897-4756
  25. 25. Fishilevich S. Amir L. Fridman Y. Aharoni A. Alfonta L. 2009 Surface display of redox enzymes in microbial fuel cells Journal of the American Chemical Society 131 34 12052 12053 0002-7863
  26. 26. Gao, F.; Viry, L.; Maugey, M.; Poulin, P. & Mano, N. (2010). Engineering hybrid nanotube wires for high-power biofuel cells. Nature Communications, Vol. 1, No. 1, pp. 1-7, ISSN 2041-1723
  27. 27. Grolleau C. Coutanceau C. Pierre F. Léger J. M. 2008 Effect of potential cycling on structure and activity of Pt nanoparticles dispersed on different carbon supports Electrochimica Acta 53 24 7157 7165 0013-4686
  28. 28. Gupta G. Rajendran V. Atanassov P. 2004 Bioelectrocatalysis of oxygen reduction reaction by laccase on gold electrodes Electroanalysis 16 13-14 1182 1185 1521-4109
  29. 29. Habrioux A. Merle G. Servat K. Kokoh K. B. Innocent C. Cretin M. Tingry S. 2008 Concentric glucose/O2 biofuel cell Journal of Electroanalytical Chemistry 622 1 97 102 1572-6657
  30. 30. Habrioux A. Napporn T. Servat K. Tingry S. Kokoh K. B. 2010 Electrochemical characterization of adsorbed bilirubin oxidase on Vulcan XC 72R for the biocathode preparation in a glucose/O2 biofuel cell. Electrochimica Acta 55 26 7701 7705 0013-4686
  31. 31. Habrioux, A.; Servat, K.; Tingry, S. & Kokoh, K.B. (2009a). Enhancement of the performances of a single concentric glucose/O2 biofuel cell by combination of bilirubin oxidase/Nafion cathode and Au-Pt anode. Electrochemistry Communications, Vol. 11, No. 1, pp. 111-113, ISSN 1388-2481
  32. 32. Habrioux A. Sibert E. Servat K. Vogel W. Kokoh K. B. Alonso-Vante N. 2007 Activity of Platinum-Gold Alloys for Glucose Electrooxidation in Biofuel Cells. The Journal of Physical ChemistryB, 111 34 10329 10333 1520-6106
  33. 33. Habrioux A. Vogel W. Guinel M. Guetaz L. Servat K. Kokoh K. B. Alonso-Vante N. 2009b Structural and electrochemical studies of Au-Pt nanoalloys Physical Chemistry Chemical Physics, 11 18 3573 3579 1463-9076
  34. 34. Heller A. 2004 Miniature biofuel cells Physical Chemistry Chemical Physics 6 2 209 216 1463-9076
  35. 35. Jin C. Chen Z. 2007 Electrocatalytic oxidation of glucose on gold-platinum nanocomposite electrodes and platinum-modified gold electrodes Synthetic Metals 157 13-15 592 596 0379-6779
  36. 36. Kang C. Shin H. Zhang Y. Heller A. 2004 Deactivation of bilirubin oxidase by a product of the reaction of urate and O2 Bioelectrochemistry 65 1 83 88 1567-5394
  37. 37. Karnicka K. Miecznikowski K. Kowalewska B. Skunik M. Opallo M. Rogalski J. Schuhmann W. Kulesza P. J. 2008 ABTS-Modified Multiwalled Carbon Nanotubes as an Effective Mediating System for Bioelectrocatalytic Reduction of Oxygen Analytical Chemistry 80 19 7643 7648 0003-2700
  38. 38. Katz E. Willner I. 2003 A Biofuel Cell with Electrochemically Switchable and Tunable Power Output. Journal of the American Chemical Society 125 22 6803 6813 0002-7863
  39. 39. Kenausis G. Chen Q. Heller A. 1997 Electrochemical glucose and lactate sensors based on "wired" thermostable soybean peroxidase operating continuously and stably at 37 °C. Analytical Chemistry 69 6 1054 1060 0003-2700
  40. 40. Kerzenmacher S. Ducrée J. Zengerle R. von Stetten. F. 2008 An abiotically catalyzed glucose fuel cell for powering medical implants: Reconstructed manufacturing protocol and analysis of performance Journal of Power Sources 182 1 66 75 0378-7753
  41. 41. Kleppe K. 1966 The effect of hydrogen peroxide on glucose oxidase from Aspergillus Niger. Biochemistry 5 1 139 143 0006-2960
  42. 42. Klotzbach T. L. Watt M. Ansari Y. Minteer S. D. 2008 Improving the microenvironment for enzyme immobilization at electrodes by hydrophobically modifying chitosan and Nafion® polymers. Journal of Membrane Science 311 1-2 81 88 0376-7388
  43. 43. Kokoh, K.B.; Léger, J.M.; Beden, B.; Huser, H. & Lamy, C. (1992a). "On line" chromatographic analysis of the products resulting from the electrocatalytic oxidation of d-glucose on pure and adatoms modified Pt and Au electrodes-Part II. Alkaline medium. Electrochimica Acta, Vol. 37, No. 11, pp. 1909-1918, ISSN 0013-4686
  44. 44. Kokoh K. B. Léger J. M. Beden B. Lamy C. 1992bOn line" chromatographic analysis of the products resulting from the electrocatalytic oxidation of d-glucose on Pt, Au and adatoms modified Pt electrodes-Part I. Acid and neutral media. Electrochimica Acta, 37 8 1333 1342 0013-4686
  45. 45. Li H. Webb S. P. Ivanic J. Jensen J. H. 2004 Determinants of the Relative Reduction Potentials of Type-1 Copper Sites in Proteins. Journal of the American Chemical Society 126 25 8010 8019 0002-7863
  46. 46. Ma Y. Balbuena P. B. 2007 Designing oxygen reduction catalysts: Insights from metalloenzymes Chemical Physics Letters 440 1-3 130 133 0009-2614
  47. 47. Mano N. Kim H. H. Heller A. 2002aOn the Relationship between the Characteristics of Bilirubin Oxidases and O2 Cathodes Based on Their "Wiring". The Journal of Physical Chemistry B, 106 34 8842 8848 1520-6106
  48. 48. Mano N. Kim H. H. Zhang Y. Heller A. 2002b An Oxygen Cathode Operating in a Physiological Solution. Journal of the American Chemical Society 124 22 6480 6486 0002-7863
  49. 49. Mano N. Mao F. Heller A. 2002c A Miniature Biofuel Cell Operating in A Physiological Buffer. Journal of the American Chemical Society 124 44 12962 12963 0002-7863
  50. 50. Mano, N.; Mao, F. & Heller, A. (2004). Electro-oxidation of glucose at an increased current density at a reducing potential. Chemical Communications, Vol. No. 18, pp. 2116-2117, ISSN 1359-7345
  51. 51. Mano N. Mao F. Heller A. 2005On the parameters affecting the characteristics of the "wired" glucose oxidase anode. Journal of Electroanalytical Chemistry, 574 2 347 357 1572-6657
  52. 52. Mano N. Soukharev V. Heller A. 2006 A laccase-wiring redox hydrogel for efficient catalysis of O2 electroreduction. The Journal of Physical ChemistryB, 110 23 11180 11187 1520-6106
  53. 53. Mao F. Mano N. Heller A. 2003Long Tethers Binding Redox Centers to Polymer Backbones Enhance Electron Transport in Enzyme "Wiring" Hydrogels. Journal of the American Chemical Society, 125 16 4951 4957 0002-7863
  54. 54. Merle G. Brunel L. Tingry S. Cretin M. Rolland M. Servat K. Jolivalt C. Innocent C. Seta P. 2008 Electrode biomaterials based on immobilized laccase. Application for enzymatic reduction of dioxygen Materials Science and Engineering: C, 28 5-6 932 938 0928-4931
  55. 55. Merle G. Habrioux A. Servat K. Rolland M. Innocent C. Kokoh K. B. Tingry S. 2009 Long-term activity of covalent grafted biocatalysts during intermittent use of a glucose/O2 biofuel cell. Electrochimica Acta 54 11 2998 3003 0013-4686
  56. 56. Minteer S. D. Liaw B. Y. Cooney M. J. 2007 Enzyme-based biofuel cells Current Opinion in Biotechnology 18 3 228 234 0958-1669
  57. 57. Möller H. Pistorius P. C. 2004 The electrochemistry of gold-platinum alloys Journal of Electroanalytical Chemistry 570 2 243 255 1572-6657
  58. 58. Moore C. M. Akers N. L. Hill A. D. Johnson Z. C. Minteer S. D. 2004 Improving the environment for immobilized dehydrogenase enzymes by modifying Nafion with tetraalkylammonium bromides. Biomacromolecules 5 4 1241 1247 1525-7797
  59. 59. Mott D. Luo J. Njoki P. N. Lin Y. Wang L. Zhong C. J. 2007 Synergistic activity of gold-platinum alloy nanoparticle catalysts Catalysis Today 122 3-4 378 385 0920-5861
  60. 60. Neto, S.; Forti, J. & De Andrade, A. (2010). An Overview of Enzymatic Biofuel Cells. Electrocatalysis, Vol. 1, No. 1, pp. 87-94, ISSN 1868-2529
  61. 61. Palmer A. E. Lee S. K. Solomon E. I. 2001 Decay of the Peroxide Intermediate in Laccase: Reductive Cleavage of the O-O Bond. Journal of the American Chemical Society 123 27 6591 6599 0002-7863
  62. 62. Palmore G. T. R. Kim H. H. 1999 Electro-enzymatic reduction of dioxygen to water in the cathode compartment of a biofuel cell Journal of Electroanalytical Chemistry 464 1 110 117 1572-6657
  63. 63. Park S. Boo H. Chung T. D. 2006 Electrochemical non-enzymatic glucose sensors Analytica Chimica Acta 556 1 46 57 0003-2670
  64. 64. Paul B. K. Mitra R. K. 2005 Water solubilization capacity of mixed reverse micelles: Effect of surfactant component, the nature of the oil, and electrolyte concentration. Journal of Colloid and Interface Science 288 1 261 279 0021-9797
  65. 65. Rao, M.L.B. & Drake, R.F. (1969). Studies of Electrooxidation of Dextrose in Neutral Media. Journal of The Electrochemical Society, Vol. 116, No. 3, pp. 334-337, ISSN 1945-7111
  66. 66. Rusling J. F. Wang B. Yun S. E. 2008Electrochemistry of redox enzymes, In: Bioelectrochemistry : Fundamentals, Experimental Techniques and Applications, P.N. Bartlett, (Ed.), 39 85Wiley, 978-0-47084-364-2New-York, U. States.
  67. 67. Schmidt, T.J.; Gasteiger, H.A. & Behm, R.J. (1999). Rotating Disk Electrode Measurements on the CO Tolerance of a High-Surface Area Pt/Vulcan Carbon Fuel Cell Catalyst. Journal of The Electrochemical Society, Vol. 146, No. 4, pp. 1296-1304, ISSN 1945-7111
  68. 68. Senthil Kumar. S. Phani K. L. N. 2009 Exploration of unalloyed bimetallic Au-Pt/C nanoparticles for oxygen reduction reaction Journal of Power Sources 187 1 19 24 0378-7753
  69. 69. Shimizu A. Kwon J. H. Sasaki T. Satoh T. Sakurai N. Sakurai T. Yamaguchi S. Samejima T. 1999 Myrothecium verrucaria Bilirubin Oxidase and Its Mutants for Potential Copper Ligands. Biochemistry 38 10 3034 3042 0006-2960
  70. 70. Shleev S. Tkac J. Christenson A. Ruzgas T. Yaropolov A. I. Whittaker J. W. Gorton L. 2005 Direct electron transfer between copper-containing proteins and electrodes Biosensors and Bioelectronics 20 12 2517 2554 0956-5663
  71. 71. Soukharev V. Mano N. Heller A. 2004 A four-electron O2-electroreduction biocatalyst superior to platinum and a biofuel cell operating at 0.88 V. Journal of the American Chemical Society 126 27 8368 8369 0002-7863
  72. 72. Stankovich M. T. Schopfer L. M. Massey V. 1978 Determination of glucose oxidase oxidation-reduction potentials and the oxygen reactivity of fully reduced and semiquinoid forms. Journal of Biological Chemistry, 253 14 4971 4979 0021-9258
  73. 73. Sun Y. Buck H. Mallouk T. E. 2001 Combinatorial Discovery of Alloy Electrocatalysts for Amperometric Glucose Sensors. Analytical Chemistry 73 7 1599 1604 0003-2700
  74. 74. Thomas T. J. Ponnusamy K. E. Chang N. M. Galmore K. Minteer S. D. 2003 Effects of annealing on mixture-cast membranes of Nafion® and quaternary ammonium bromide salts. Journal of Membrane Science 213 1-2 55 66 0376-7388
  75. 75. Timur S. Pazarlioglu N. Pilloton R. Telefoncu A. 2004 Thick film sensors based on laccases from different sources immobilized in polyaniline matrix Sensors and Actuators BChemical, 97 1 132 136 0925-4005
  76. 76. Topcagic, S. & Minteer, S.D. (2006). Development of a membraneless ethanol/oxygen biofuel cell. Electrochimica Acta, Vol. 51, No. 11, pp. 2168-2172, ISSN 0013-4686
  77. 77. Tsujimura S. Tatsumi H. Ogawa J. Shimizu S. Kano K. Ikeda T. 2001 Bioelectrocatalytic reduction of dioxygen to water at neutral pH using bilirubin oxidase as an enzyme and 2,2’-azinobis (3-ethylbenzothiazolin-6-sulfonate) as an electron transfer mediator. Journal of Electroanalytical Chemistry 496 1-2 69 75 1572-6657
  78. 78. Vogel W. Bradley J. Vollmer O. Abraham I. 1998 Transition from five-fold symmetric to twinned FCC gold particles by thermally induced growth The Journal of Physical Chemistry B 102 52 10853 10859 1520-6106
  79. 79. Vogel W. Tesche B. Schulze W. 1983 X-ray structure and optical properties of silver films prepared by condensation of pre-formed Ag-clusters Chemical Physics 74 1 137 142 0301-0104
  80. 80. Wang J. 2007 Electrochemical Glucose Biosensors Chemical Reviews 108 2 814 825 0009-2665
  81. 81. Wang Z. Liu S. Wu P. Cai C. 2009 Detection of glucose based on direct electron transfer reaction of glucose oxidase immobilized on highly ordered polyaniline nanotubes Analytical Chemistry 81 4 1638 1645 0003-2700
  82. 82. Willner I. Heleg-Shabtai V. Blonder R. Katz E. Tao G. Backmann A. F. Heller A. 1996 Electrical wiring of glucose oxidase by reconstitution of FAD-modified monolayers assembled onto Au-electrodes Journal of the American Chemical Society 118 42 10321 10322 0002-7863
  83. 83. Wilson R. Turner A. P. F. 1992 Glucose oxidase: an ideal enzyme Biosensors and Bioelectronics 7 3 165 185 0956-5663
  84. 84. Woods R. 1971 The surface composition of platinum-gold alloys Electrochimica Acta 16 5 655 658 0013-4686
  85. 85. Yahiro A. T. Lee S. M. Kimble D. O. 1964Bioelectrochemistry: I. Enzyme utilizing bio-fuel cell studies. Biochimica et Biophysica ActaBBA)- Specialized Section on Biophysical Subjects, 88 2 375 383 0926-6577
  86. 86. Zagal J. H. Griveau S. Silva J. F. Nyokong T. Bedioui F. 2010 Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions Coordination Chemistry Reviews 254 23-24 2755 2791 0010-8545
  87. 87. Zebda A. Renaud L. Cretin M. Innocent C. Pichot F. Ferrigno R. Tingry S. 2009a Electrochemical performance of a glucose/oxygen microfluidic biofuel cell Journal of Power Sources 193 2 602 606 0378-7753
  88. 88. Zebda, A.; Renaud, L.; Cretin, M.; Pichot, F.; Innocent, C.; Ferrigno, R. & Tingry, S. (2009b). A microfluidic glucose biofuel cell to generate micropower from enzymes at ambient temperature. Electrochemistry Communications, Vol. 11, No. 3, pp. 592-595, ISSN 1388-2481
  89. 89. Zhang, M.; Mullens, C. & Gorski, W. (2007). Coimmobilization of dehydrogenases and their cofactors in electrochemical biosensors. Analytical Chemistry, Vol. 79, No. 6, pp. 2446-2450, ISSN 0003-2700
  90. 90. Zhu, Z.; Momeu, C.; Zakhartsev, M. & Schwaneberg, U. (2006). Making glucose oxidase fit for biofuel cell applications by directed protein evolution. Biosensors and Bioelectronics, Vol. 21, No. 11, pp. 2046-2051, ISSN 0956-5663

Written By

Habrioux Aurélien, Servat Karine, Tingry Sophie and Kokoh Boniface

Submitted: 20 October 2010 Published: 01 August 2011