Open access peer-reviewed chapter - ONLINE FIRST

Water Remediation by G-/GO-Based Photocatalysts

By Humaira Seema

Submitted: May 21st 2018Reviewed: February 12th 2019Published: September 23rd 2019

DOI: 10.5772/intechopen.85144

Downloaded: 45

Abstract

Graphene, a two-dimensional sheet of sp2 hybridized carbon atoms, has shown to be the most fascinating and promising option among nanomaterials for a variety of applications, because of its unique structure and tunable physiochemical properties. It can be either in the pure form or in its modified derivatives that include graphene oxide (GO), reduced graphene oxide (rGO), graphene-metal nanoparticle composites, graphene-polymer hybrids, and graphene/organic structures that showed improved results while maintaining inherent properties of the material. These modified nanostructures have a variety of applications as catalysts, energy storage/conversion, antimicrobial, and water decontaminant. In the field of environmental science, graphene has been widely used for molecular sieving involving gas phase separation and organic waste removal from water, due to its biocompatibility, various functional groups, and accessible surface area. Modified graphene can also serve as a semiconductor that can increase the efficiency of the photocatalytic ecosystems that results in the inactivation of the microorganisms causing the organic chemicals to degrade.

Keywords

  • graphene
  • environmental
  • remediation
  • photocatalyst
  • water

1. Introduction

Recently photocatalysis by using semiconductors has fascinated universal consideration for its energy-related and environmental applications. Nevertheless, the decrease in the efficiency of the photocatalysis restricted its practical applications because of the prompt reunion of photogenerated electrons and holes. Thus, to decrease the reunion of charge carriers is significant for improvement of semiconductor photocatalysis. Among numerous approaches, water remediation has been done by rGO-/GO-based materials which are the most favorable candidates due to their high capacity of dye adsorption, prolonged light absorption range, improved separation of charge carriers, and transportation properties leading to improved photoconversion efficiency of the photocatalytic materials [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74].

1.1 Graphene (rGO)-based photocatalysts

Various numbers of graphene-based photocatalysts have been prepared with its derivatives which mainly comprise metal oxides (e.g., P25 [1, 8], TiO2 [9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 3637], ZnO [17, 39, 40, 41, 42, 43], CuO [44], SnO2 [13, 45], WO3 [46]), metals (e.g., Cu [51], Au [52]), metal-metal oxides (e.g., Ag-TiO2 [35]), upconversion material—P25 (e.g., YF3:Yb3+,Tm3+—TiO2 [38]), salts (e.g., CdS [47, 48, 49], ZnS [50], ZnFe2O4 [53], MnFe2O4 [54], NiFe2O4 [55], CoFe2O4 [56], Bi2WO6 [57, 58, 59], Bi2MoO6 [60], InNbO4 [61], ZnSe [63]), Ag/AgCl [62]), and other carbon material (e.g., CNT [64]).

1.2 Graphene oxide (GO)-based photocatalysts

Graphene oxide (GO) has recently received considerable attention due to oxygen-containing functional groups which increase its solubility in solvents for the preparation of GO-based nanocomposites required for photodegradation of pollutants [65, 66, 67, 68, 69, 70, 71, 72, 73, 74]. GO-based nanocomposites mainly include metal oxides (TiO2) [66, 67, 68, 69, 70, 71, 72], metal-free polymers [73], and silver/silver halides [74].

2. Preparation of rGO-/GO-based composite photocatalysts

Some of the commonly used synthesis techniques include in situ growth strategy, solution mixing, hydrothermal/ solvothermal, and microwave-assisted process.

2.1 In situ growth strategy

This method is usually used to prepare reduced graphene oxide-/graphene oxide-based metal composites. Zhang et al. reported that TiO2/graphene composite photocatalyst [14] is synthesized by a simple liquid-phase deposition technique. Moreover, adopting a similar approach, Wang et al. prepared nanocarbon/TiO2 nanocomposites where titania nanoparticles were decorated by thermal reaction on the surfaces of three different dimensional nanocarbons [9]. While in thermal reduction method, TiO2/graphene composite [12] with a remarkable visible light photocatalytic activity was prepared by Zhang et al. using a heat treatment method of GO, where GO changed to reduced graphene oxide. Uniform ZnO nanoparticles were found on functionalized graphene sheets evenly via thermal decay of mixture of zinc salt, graphene oxide, and poly(vinyl pyrrolidone) [39].

Furthermore, Sn2+ or Ti3+ ions were converted to oxides at low temperatures, while GO was reduced to reduced graphene oxide by tin or titanium salts in redox method [13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45]. In our recent work, we prepared SnO2-G nanocomposite which displayed higher photocatalytic activity in sunlight as compared to bare metal oxide nanoparticles as shown in Figure 1 [45]. Similarly reduced graphene oxide-zinc oxide composite was prepared where zinc ions were decorated on GO sheets and transformed to metal oxide nanoparticles by using chemical reagents at 150°C. Reduced graphene oxide-ZnO photocatalyst is formed by reducing the graphene oxide [43].

Figure 1.

Time-dependent absorption spectra of MB solution during UV light irradiation in the presence of (a) SnO2 and (b) reduced graphene oxide-SnO2 and during sunlight irradiation in the presence of (c) SnO2 and (d) reduced graphene oxide-SnO2. Reprinted with permission of the publisher [45].

Li et al. prepared uniform mesoporous titania nanospheres on reduced graphene oxide layers via a process of a template-free self-assembly [20]. Du et al. [21] also developed the macro-mesoporous titania-reduced graphene oxide composite film by a confinement of a self-assembly process as shown in Figure 2.

Figure 2.

Schematic view for the preparation of a macro-mesoporous TiO2-reduced graphene oxide composite film. Reprinted with permission of the publisher [21].

Moreover Kim et al. synthesized strongly coupled nanocomposites of layered titanate and graphene by electrostatically derived self-assembly between negatively charged G nanosheets and positively charged TiO2 nanosols, followed by a phase transition of the anatase TiO2 component into layered titanate [37]. Chen et al. prepared graphene oxide/titania composites by using the self-assembly technique [72].

While Cu ion-modified reduced graphene oxide [51] prepared by an immersion technique displayed a high photocatalytic activity, gold nanoparticles were decorated on the surface of the reduced graphene oxide through spontaneous chemical reduction of HAuCl4 by GOR [52] as shown in Figure 3.

Figure 3.

Possible mechanism of photosensitized degradation of dyes over a rGO Cu composite under visible light irradiation. Reprinted with permission of the publisher [52].

Bi2WO6/reduced graphene oxide photocatalysts were successfully prepared via in situ refluxing method in the presence of GO [57]. Zhang et al. presented reduced graphene oxide sheet grafted Ag@AgCl plasmonic photocatalyst with high activity via a precipitation reaction followed by reduction [62]. TiO2-GO was well prepared at 80°C by using GO and titanium sulfate as precursors [66].

Liu et al. have established a process of water/toluene two-phase for self-assembling TiO2 nanorods on graphene oxide [69, 70]. Jiang et al. prepared GO/titania composite by in situ depositing titania on GO through liquid-phase deposition, followed by a calcination at 200°C [71].

GO nanostructures are prepared by modified Hummer’s method, which has promising applications in photocatalysis [65].

2.2 Solution mixing method

It has been widely used to prepare graphene-based photocatalysts. Previously, titania nanoparticles and GO colloids have been mixed by ultrasonication followed by ultraviolet (UV)-assisted photocatalytic reduction of GO to yield graphene-titania nanocomposites [18, 23, 31].

Akhavan and Ghaderi used a similar strategy to prepare the titania/reduced graphene oxide composite thin film [25].

Guo et al. [28] prepared TiO2/graphene composite via sonochemical method. GO/g-C3N4 with efficient photocatalytic capability was also fabricated by the same sonochemical approach [73].

ZnO and GO mixture was dispersed by ultrasonication followed by chemical reduction of GO to graphene ultimately leading to synthesize ZnO/graphene composite [40]. The G-hierarchical ZnO hollow sphere composites are synthesized by Luo et al. by using a simple ultrasonic treatment of the solution [43].

Cheng et al. [40] presented a new facile ultrasonic approach to prepare graphene quantum dots (GQDs), which exhibited photoluminescent in a water solution. The water/oil system is used by Zhu et al. [74] to produce graphene oxide enwrapped Ag/AgX (X = Br, Cl) composites. Graphene oxide and silver nitrate solution were added to chloroform solution of surfactants stirring condition at room temperature to produce hybrid composites which displayed high photocatalytic activity under visible light irradiation as shown in Figure 4. Titania/graphene oxide composites were synthesized using one-step colloidal blending method [68].

Figure 4.

(A) Photocatalytic activities of silver/silver bromide (a) and silver/silver bromide/GO (b) nanospecies for photodegradation of MO molecules under visible light irradiation and (B) those of the Ag/AgCl (a) and Ag/AgCl/GO (b) nanospecies. Reprinted with permission of the publisher [74].

2.3 Hydrothermal/solvothermal method

This one-pot process can lead to highly crystalline nanostructures, which operates at elevated temperatures in an autoclave to generate high pressure, without calcination, and at the same time GO reduced to rGO. Typically, graphene-based composites, e.g., P25 [1, 8], TiO2 [15, 16, 24, 29, 30, 32, 33, 34], Ag-TiO2 [35], UC-P25 [38], WO3 [46], CdS [49], ZnFe2O4 [53], MnFe2O4 [54], NiFe2O4 [55], Bi2WO6 [58, 59], Bi2MoO6 [60], InNbO4 [61], and ZnSe [63], have been prepared by the hydrothermal process, while others such as TiO2 [11, 22, 26, 27], CuO [44], CdS [48], and CoFe2O4 [56] are prepared by the solvothermal process.

Li et al. have prepared P25-G nanocomposite using GO and P25 as raw materials via hydrothermal technique [8]. As illustrated in Figure 5, the photocatalysis determines that composite showed improved activity toward the photodegradation of methylene blue (MB).

Figure 5.

Photodegradation of MB under (a) UV light (λ = 365 nm) and (b) visible light (λ > 400 nm) over (1) P25, (2) P25-CNTs, and (3) P25-GR photocatalysts, respectively. (c) Schematic structure of P25-GR and process of the photodegradation of MB over P25-GR. (d) Bar plot showing the remaining MB in solution: (1) initial and equilibrated with (2) P25, (3) P25-CNTs, and (4) P25-GR in the dark after 10-min stirring. Pictures of the corresponding dye solutions are on the top for each sample. Reprinted with permission of the publisher [8].

Lee et al. synthesized graphene oxide (GO)-wrapped TiO2 nanoparticles by combining positively charged TiO2 nanoparticles with negatively charged GO nanosheets, as shown in SEM images in Figure 6. Furthermore, it demonstrates the reduction of graphene oxide to reduced graphene oxide and the crystallization of amorphous titania nanoparticles which occurred after a hydrothermal treatment.

Figure 6.

(A) Schematic illustration of synthesis steps for graphene-wrapped anatase TiO2 nanoparticles (NPs) and corresponding SEM images of (B) bare amorphous TiO2 NPs, (C) GO-wrapped amorphous TiO2 NPs, and (D) graphene-wrapped anatase TiO2 NPs (scale bar: 200 nm); (E) the suggested mechanism for the photocatalytic degradation of MB by graphene-wrapped anatase TiO2 NPs under visible light irradiation. Reprinted with permission of the publisher [8].

2.4 Microwave-assisted method

In situ microwave irradiation is a facile method which has been used for the simultaneous formation of metal oxide (e.g., TiO2 [17], ZnO [17, 41], CdS [47], ZnS [50]) and reduction of GO. The drawback of this process is that it did not show its fine control over the uniform size and surface distribution of nanoparticles on G surfaces.

2.5 Other methods

In addition to the abovementioned examples, graphene-based photocatalysts are synthesized by developing new synthetic strategies, e.g., electrospinning [10] and chemical vapor deposition (CVD) [64].

Zhao et al. pillared reduced graphene oxide platelets with carbon nanotubes using the CVD method with acetonitrile as the carbon source and nickel nanoparticles as the catalysts as shown in Figure 7.

Figure 7.

(A) Photocatalytic degradation for RhB under different experimental conditions with catalysts GOCNT-15-4 and P25. (B) Photocatalytic properties of different samples in degrading RhB. (C) Experimental steps of pillaring GO and RGO platelets with CNTs while energy diagram showing the proposed mechanism of photosensitized degradation of RhB under visible light irradiation. Reprinted with permission of the publisher [64].

Photocatalytic TiO2 films were prepared by Yoo et al. using RF magnetron sputtering and GO solutions with different concentrations of GO in ethanol which were coated on TiO2 films [67]. Graphene film was formed on the surface of TiO2 nanotube arrays through in situ electrochemical reduction of GO dispersion by cyclic voltammetry [19].

3. Photocatalysis

Due to widespread environmental applications, photocatalysis has fascinated an increasing consideration. The graphene-/graphene oxide-based photocatalyst revealed a significant improvement of photocatalytic degradation of methylene blue (MB) [1, 8, 11, 12, 15, 18, 21, 22, 26, 28, 30, 31, 32, 33, 35, 36, 40, 41, 43, 45, 48, 50, 52, 53, 54, 55, 56, 60, 61, 67, 68, 69], rhodamine B (RhB) [13, 20, 24, 27, 32, 42, 44, 51, 52, 56, 57, 58, 59, 62, 64, 73], methyl orange (MO) [9, 10, 14, 37, 38, 49, 63, 66, 71, 72, 74], anthracene-9-carboxylic acid (9-AnCOOH) [19], phenol [22, 54], 2,4-dichlorophenoxyacetic acid (2,4-D) [23], 2,4-dichlorophenol [61, 73], malachite green (MG) [29], 2-propanol [34], rhodamine 6G (Rh 6G) [39], rhodamine B 6G (RhB 6G) [46], orange ll [52], 2,4-dichlorophenol (2,4-DCP) [61], acid orange 7(AO 7) [64], and resazurin (RZ) [65], as well as photocatalytic reduction of Cr(VI) [17, 47, 71], along with photocatalytic antibacterial activity for killing E. coli bacteria [25] by UV [1, 8, 9, 10, 13, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24, 26, 28, 29, 30, 31, 32, 33, 34, 37, 39, 40, 41, 42, 43, 44, 45, 50, 54, 65, 66, 67, 68, 69, 70, 71], as well as visible irradiation [1, 8, 9, 10, 11, 12, 13, 15, 16, 20, 22, 25, 27, 30, 31, 32, 33, 35, 36, 37, 38, 42, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 67, 68, 72, 73, 74], in water which are briefly summarized in Table 1.

PhotocatalystsMass fractionPreparation strategyPhotocatalytic experimentsPerformances as compared to reference photocatalystType of irradiationReferences
(1) rGO-based
P25-rGO0.2% GHydrothermal methodPhotodegradation of MB1.17 times higher than P25; DP of 60%UV1
5%1.50 times
30%0.97 times
0.2%1.42 times higher than P25; DP of 28%Visible
5%2.32 times
30%0.75 times
P25-rGO1.0% GHydrothermal methodPhotodegradation of MB3.40 or 1.21 times higher than P25 or P25-CNTs; DP of 25% or 70%, respectively (2% = 90 min)UV2
4.33 or 1.18 times higher than P25 or P25-CNTs; DP of 15% or 55%, respectively (2% = 90 min)Visible
TiO2-rGO10 mg GIn situ growth strategy (thermal treatment)Degradation of MO2.05 times higher than P25; DP of 40%UV3
5.46 times higher than P25; 15%Visible
TiO2-rGO0.75% GElectrospin-ning methodDegradation of MO1.51 times higher than TiO2; DP of 54%UV4
2.04 times higher than TiO2; DP of approx. 22%Visible
TiO2-rGO10 mg GSolvothermal methodPhotodegradation of MB2.32 or 1.50 times higher than pure TiO2 or P25; DP of 25% or 39%, respectivelyVisible5
30 mg3.0 or 1.92 times
50 mg2.88 or 1.84 times
TiO2-rGO10 mg GIn situ growth strategy (thermal reduction method)Photodegradation of MB7.0 times higher than pure P25; DP of 10%Visible6
TiO2-rGONo dataIn situ growth strategy (redox method)Photodegradation of RhB1.16 times higher than P25 reaction rate constant = 0.0049 min−1Visible7
0.53 times higher than P25 reaction rate constant = 0.043 min−1UV
SnO2-rGO2.24 times higher than P25 reaction rate constant = 0.0049 min−1Visible
0.62 times higher than P25 reaction rate constant = 0.043 min−1UV
TiO2-rGO20 mg GIn situ growth strategy (simple liquid-phase deposition method)Photodegradation of MO1.89 times higher than P25 and graphene; DP of 45%UV8
TiO2-rGONo dataHydrothermal methodPhotodegradation of MB13.04 or 10.62 times higher than P25 or anatase TiO2; reaction rate constant = 0.0026 min−1or 0.0032 min-1, respectivelyVisible9
TiO2-rGO20: 1Hydrothermal methodPhotodegradation of RhB1.63 times higher than P25; DP of 52%UV10
3.33 times higher than P25; DP of 15%Visible
TiO2-rGO0.8% GMicrowave-assisted methodPhotocatalytic reduction of Cr(VI)1.09 or 1.30 times higher than pure TiO2 or commercial P25 = removal rate of 83% or 70%, respectivelyUV11
rGO-w-TiO21:10Solution mixing methodPhotodegradation of MB1.25 times higher than P25; DP of 80%UV12
TiO2-rGO filmNo dataCyclic voltammetric reduction methodPhotodegradation of anthracene-9-carboxylic acid (9-AnCOOH)2.13 times higher than bare TiO2 nanotubes; DP of 46%UV13
TiO2-rGO6.5% GIn situ growth strategy (self-assembly synthesis)Photodegradation of RhB3.92 times higher than TiO2; DP of 25%UV-vis14
TiO2-rGO0.6% GIn situ growth strategy (self-assembly method)Photodegradation of MB1.57 times higher than TiO2; reaction rate constant = 0.045 min−1UV15
TiO2-rGONo dataSolvothermal methodPhotodegradation of phenol1.68 times higher than P25; DP of 48%UV16
3.10 times higher than P25; DP of 20%Visible
Photodegradation of MB3.5 times higher than P25; DP of 20%Visible
TiO2-rGO filmNo dataSolution mixing methodPhotodegradation of 2,4-dichlor-ophen-oxyacetic acid (2,4-D)4.0 times higher than TiO2 film; reaction rate constant = 0.002 min−1UV17
TiO2-rGO10% GOHydrothermal methodPhotodegradation of RhB4.0 or 2.94 times higher than pure TiO2 or P25; reaction rate constant = 0.05 or 0.068 min−1UV18
TiO2-rGONo dataSolution mixing methodPhotocatalytic antibacterial activity for killing E. coli bacteria7.55 times higher than TiO2; reaction rate constant = 0.0086 min−1Visible19
TiO2-rGO0.3 mg GOSolvothermal methodPhotodegradation of MB2.08 times higher than P25; DP of 40.8%UV20
TiO2-rGONo dataSolvothermal methodPhotodegradation of RhB2.79 times higher than P25; reaction rate constant = 0.0162 min−1Visible21
TiO2-rGO75% GSonochemical methodPhotodegradation of MB2.57 times higher than P25; reaction rate constant = 0.0054 min−1UV22
TiO2-rGO10% GHydrothermal methodPhotodegradation of Malachite green3.09 times higher than TiO2 nanotubes; reaction rate constant = 0.0218 min−1UV23
TiO2-rGONo dataHydrothermal methodPhotodegradation of MB1.46 times higher than P25; DP of 65%UV24
2.41 times higher than P25; DP of 29%Visible
rGO @TiO21:3Solution mixing methodPhotodegradation of MB4.0 or 1.73 times higher than P25 or physical mixture of G-P25 (1:3); DP of 13% or 30%, respectivelyVisible25
Photodegradation of MB2.93–2.20 times higher than P25 or physical mixture of G-P25 (1:3); DP of 30–40%UV
TiO2-B-doped rGO2 mg GHydrothermal methodPhotodegradation of MB4.30 times higher than TiO2; reaction rate constant = 0.010 min−1UV-vis26
Photodegradation of RhB1.6 times higher than TiO2; reaction rate constant = 0.005 min−1
TiO2-N-doped rGOPhotodegradation of MB2.4 times higher than TiO2; reaction rate constant = 0.010 min−1
Photodegradation of RhB3.2 times higher than TiO2; reaction rate constant = 0.005 min−1
TiO2-rGO-TiO20.01 g GHydrothermal methodPhotodegradation of MB4 times higher than TiO2UV-vis27
TiO2-rGO/MCM-410.05% GHydrothermal method and Thermal methodPhotodegradation of 2-propanol1.4 times higher than TiO2/MCM-41; conversion rate of 26%UV28
0.15%1.7 times
0.4%1.27 times
0.6%0.96 times
Ag-TiO2-rGONo dataHydrothermal and solution mixing methodPhotodegradation of MBEnhancementVisible29
RutileTiO2-GQD/anatase TiO2-GQD0.05 g GSolution mixing methodDegradation of MBEnhancement for rutile TiO2/GQD than anatase TiO2/GQDVisible30
Layered titanate rGONo dataIn situ growth strategy (self-assembly method)Photodegradation of MOEnhancement as compared to bulk-layered titanates or nanocrystalline-layered titanateUV-vis31
UC-P25-rGO
UC = YF3:Yb3+,Tm3+
4 mg GOHydrothermal methodPhotodegradation of MO2.88 or times higher than P25 or P25-G or UC-P25; DP of 27% or 53% or 46%, respectivelyVisible32
ZnO-rGO0.6% GMicrowave-assisted methodPhotocatalytic reduction of Cr(VI)1.12 or 0.92 times higher than pure ZnO or P25; removal rate of 58 or 70%, respectivelyUV33
0.8% G1.46 or 1.21 times
1.0% G1.68 or 1.40 times
ZnO-FGS0.1 g GOIn situ growth strategy (thermal method)Photodegradation of Rh 6GEnhancementUV34
ZnO-rGO0.1% GSolution mixing method (sonochemical)Photodegradation of MB2.13 times higher than ZnO; reaction rate constant = 0.022 min−1UV35
0.5%2.54 times
1.0%3.13 times
2.0%4.45 times
3.0%4.13 times
5.0%3.27 times
ZnO-rGO1.1% GMicrowave-assisted methodPhotodegradation of MB1.29 times higher than ZnO; DP of 68%UV36
ZnO@ rGOIn situ growth strategy (chemical deposition method)Photodegradation of RhB1.05 times higher than ZnO; DP of 95%UV37
1.02 times higher than ZnO; DP of 98%Visible
ZnO-rGO3.56% GSolution mixing method (ultrasonic method)Photodegradation of MB2.25 times higher than ZnO; DP of 40%UV38
CuO-rGONo dataSolvothermal methodPhotodegradation of RhB in the presence of H2O22.50 times higher than ZnO; DP of 40%UV39
SnO2-rGO5% GIn situ growth strategy (redox method)Photodegradation of MB0.40 or times higher than SnO2; DP of 100%UV40
24.86 times higher than SnO2; DP of 4%Visible
WO3-rGO3.5% GHydrothermal methodPhotodegradation of RhB 6G2.2 or 53 times higher than WO3 nanorods or WO3 particles; reaction rate constant = 0.00167or 0.000069 min−1, respectivelyVisible41
CdS-rGO1.5% GMicrowave-assisted methodPhotocatalytic reduction of Cr(VI)1.16 times higher than CdS = removal rate of 79%Visible42
CdS-rGO5% GSolvothermal methodPhotodegradation of MB2.5 times higher than CdS; DP of 37.6%Visible43
CdS-rGO0.01:1Hydrothermal methodPhotodegradation of MO7.86 times higher than CdS; reaction rate constant = 0.0075 min−1Visible44
ZnS-rGONo dataMicrowave-assisted methodPhotodegradation of MB4 times higher than P25; DP of 25%UV45
Cu-rGONo dataIn situ growth strategy (immersion method)Photodegradation of RhB2.94 or 30.61 times higher than P25 or graphene; reaction rate constant = 0.0051 min−1 or 0.00049 min−1, respectivelyVisible46
Au-rGONo dataIn situ growth strategy (chemical reduction)Photodegradation of RhB1.77 times higher than P25; reaction rate constant = 0.0049 min−1Visible47
Photodegradation of MB8.36 times
Photodegradation of orange II0.19 times
ZnFe2O4-rGO20% GHydrothermal methodPhotodegradation of MB in the presence of H2O24.50 times higher than ZnFe2O4 (DP of 22% = 90 min)Visible48
MnFe2O4-rGO30% GHydrothermal methodPhotodegradation of MB9.62 times higher than MnFe2O 4 ; DP of 10%Visible49
Photodegradation of MB1.33 times higher than MnFe2O 4 ; DP of 75%UV
Photodegradation of phenol1.13 times higher than MnFe2O 4 ; DP of 75%UV
NiFe2O4-rGO25% GHydrothermal methodPhotodegradation of MBEnhancement as compared to NiFe2O 4 ; reaction rate constant almost zero (no photocatalytic activity)Visible50
CoFe2O4-rGONo dataSolvothermal methodPhotodegradation of RhB and MBEnhancementVisible51
Bi2WO6-rGO1% GIn situ growth strategy (refluxing method)Photodegradation of RhB1.30 times higher than Bi2WO6; DP of 50%Visible52
2.5%1.40 times
5%1.80 times
10%1.10 times
15%0.80 times
Bi2WO6-rGO1% GHydrothermal methodPhotodegradation of RhBEnhancement as compared to Bi2WO6Visible53
Bi2WO6-rGONo dataHydrothermal methodPhotodegradation of RhB2.04 times higher than Bi2WO6; DP of 44% in 4 minVisible54
Bi2MoO6-rGO0.5% GHydrothermal methodPhotodegradation of MB2.45 times higher than pure Bi2MoO6; reaction rate constant 0.0037 min−1Visible55
1%3.67 times
InNbO4-rGONo dataHydrothermal methodPhotodegradation of MB1.87 times higher than InNbO4; reaction rate constant = 0.0185 min−1Visible56
Photodegra-dation of 2,4-dichloro-phenol2.10 times higher than InNbO4 reaction rate constant = 0.0256 min−1
Ag@AgCl-rGO0.22% GSolution mixing methodPhotodegradation of RhB3.88 times higher than Ag@AgCl reaction rate constant = 0.060 min−1Visible57
0.44%4.55 times
1.56%5.1 times
ZnSe-N-doped rGO18 mg GHydrothermal methodPhotodegradation of MOEnhancement as compared to ZnSe; (no photocatalytic activity)Visible58
CNT-rGONo dataChemical vapor deposition (CVD) methodPhotodegradation of RhB4.28 times higher than P25; reaction rate constant = 0.0049 min−1Visible59
(2) GO-based
GO1 mg GOSolution mixing method (modified Hummers’ method)Photocatalytic reduction of resazurin (RZ)No dataUV60
TiO2-GONo dataIn situ growth strategyPhotodegradation of MO2.27 times higher than pure P25; DP of 38.4%UV61
TiO2-GO0.03 mg GORF magnetron sputtering followed by coatingPhotodegradation of MB2.5 times higher than TiO2; DP of 20%UV62
1.75 timesVisible
TiO2-GO1.2% GOSolution mixing method (simple colloidal blending method)Photodegradation of MB4.51 times higher than P25 reaction rate constant = 0.0084 min−1UV63
4.3%4.98 times
8.2%8.59 times
1.2%1.36 times higher than P25 reaction rate constant = 0.0033 min−1Visible
4.3%3.03 times
8.2%7.15 times
TiO2-GO50 mg GOIn situ growth strategyPhotodegradation of MB1.41 times higher than P25; DP of 70%UV64
TiO2-GO500 mg GOIn situ growth strategy (two phase assembling method)Photodegradation of acid orange 7 (AO 7)11.59 times higher than P25 reaction rate constant = 0.0182 min−1UV65
TiO2-GONo dataIn situ growth strategy (thermal treatment method)Photodegradation of MO7.44 times higher than P25; reaction rate constant = 0.0426 min−1UV66
Photocatalytic reduction of Cr(VI)5.44 times higher than P25; conversion rate = 0.0127 min−1
TiO2-GO0.13% C elementIn situ growth strategy (self-assembly method)Photodegradation of MO1.18 times higher than pure P25; DP of 22%Visible67
0.14%1.59 times
0.25%1.0 times
0.51%0.82 times
g-C3N4-GO1 g GOSolution mixing method (sonochemical method)Photodegradation of RhB and 2,4-dichloro-phenol1.90 times higher than g-C3N4; DP of 49.5%Visible68
Ag/AgCl/GONo dataSolution mixing method (surfactant-assisted assembly protocol via an oil/water microemulsion)Photodegradation of MO2.84 times higher than Ag/AgCl; DP of 25%Visible69
Ag/AgBr/GOPhotodegradation of MO3.40 times higher than Ag/AgBr; DP of 25%Visible

Table 1.

Photocatalytic degradation of pollutants.

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Humaira Seema (September 23rd 2019). Water Remediation by G-/GO-Based Photocatalysts [Online First], IntechOpen, DOI: 10.5772/intechopen.85144. Available from:

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