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In recent years, water pollution has become one of the major challenges faced by humans because of consistent rise in population and industrial activities. Water pollution due to discharge from cosmetics and pharmaceutical wastes, organic dyes, and heavy metal seen as carcinogens has the potential to disrupt hormonal processes in the body. Different approaches such as chlorination, aerobic treatment, aeration, and filtration have been deployed to treat wastewaters before being discharged into the streams, lakes, and rivers. However, more attention has been accorded to treatment approaches that involve use of nanomaterial due to non-secondary pollution, energy efficiency, and ease of operation. Titanate-based perovskite (TBP) is one of the most frequently studied nanomaterials for photocatalytic applications because of its stability and flexibility in optical band-gap modification. This chapter provided an overview of basic principles and mechanisms of a semiconductor photocatalyst, and current synthesis techniques that have been used in formulating TBP nanomaterial. The effect of reaction conditions and approaches such as doping, codoping, composites, temperature, pH, precursor type, surface area, and morphology on surface defects and optical band-gap energy of TBP nanomaterial was highlighted. Importantly, the impact of surface defects and optical band-gap energy of TBP on its photocatalytic activities was discussed. Finally, how to enhance the degradation efficiency of TBP was proposed.
Faculty of Physical Sciences, Department of Physics and Astronomy, University of Nigeria Nsukka, Nigeria
National Biotechnology Development Agency, Nigeria
Priscilla Yahemba Aondona
Faculty of Physical Sciences, Department of Physics and Astronomy, University of Nigeria Nsukka, Nigeria
Amoge Chidinma Ogu
Faculty of Physical Sciences, Department of Physics and Astronomy, University of Nigeria Nsukka, Nigeria
Eugene Echeweozo
Department of Physics with Electronics, Evangel University Akaeze, Nigeria
Fabian Ifeanyichukwu Ezema
Faculty of Physical Sciences, Department of Physics and Astronomy, University of Nigeria Nsukka, Nigeria
Nanosciences African Network (NANOAFNET), iThemba LABS-National Research, South Africa
UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology, College of Graduate Studies, University of South Africa (UNISA), South Africa
*Address all correspondence to: okekestannie@gmail.com
1. Introduction
Currently, water pollution is becoming one of the most serious challenges confronting human beings due to steady increase in population, advancements in industrial activities, and urbanization [1]. Contamination of water bodies through discharge of organic pollutants such as dyes, heavy metals, and petroleum are posing a significant danger to humans as well as the aquatic ecosystem [2]. The effects of these pollutants differ and depend on the source and type; for example, organic dyes and heavy metals have been recognized as carcinogens while cosmetics and pharmaceutical waste products have been identified as endocrine disruptive agents [3]. These agents impede hormonal processes, thereby disturbing regular homeostatic reproduction, advancement, or behavior [4]. Furthermore, presence of dyes in the water bodies blocks sun from penetrating into the water bodies and lessens dissolved oxygen, therefore, causing death to photosynthetic organisms that live in the aquatic system [5].
To mitigate the impact of water pollution, scientists are making efforts to develop approaches to treat wastewaters before being discharged into rivers, streams, and underground water. Approaches such as chlorination, aerobic treatment, aeration, and filtration have been used to treat waste. However, greater attention has been given to treatment processes that involve the use of nanomaterials. Inorganic metal oxides nanoparticles (NPs) have benefits such as no secondary pollution, cost, and energy efficiency and are easily operated [6, 7]. Metal-oxide NPs have been studied for potential degradation of contaminants [8, 9, 10], heavy metals [11, 12], and inactivation of bacteria [13, 14, 15]. Many other compounds such as metal halides [16], metal nitrides [17], and metal chalcogenides [18, 19] have also been evaluated for photocatalytic applications. Among which, perovskite nanomaterial has drawn so much attention because of its wide variety of properties. Perovskite nanomaterial has indicated a broad range of electro-optical effects, piezo, ferro, and pyro-electrical properties that enable them to exhibit outstanding performances as structural, electronic, and magnetic material [20]. In addition, because of their crystalline structure, perovskites have unique chemical properties that contain a spectrum of cations to generate surface defects, which can balance unstable oxidation states [21].
Titanate-based perovskite material is among the most commonly studied perovskites for photocatalytic applications under visible light. This is because their optical band-gaps energy is easily modified and quite stable for a long period throughout a photocatalytic reaction [22]. A good number of titanium-based perovskites such as SrTiO3, MnTiO3, BaTiO3, ZnTi3, MgTiO3, and CaTiO3 have optical band-gaps energy above 3 eV [23, 24, 25], thereby allowing photocatalytic activities only under UV source. On the other hand, TBP, such as CoTiO3 and NiTiO3, have band-gap energy lower than 3 eV but their CB is below the oxidation potential [26, 27], which also limits their chances for photocatalytic applications.
Excellent photocatalyst semiconductor (SC) is expected to have excellent charge carrier mobility and charge separation to prevent recombination of electron (e) and hole (h) generated in the system [28]. Efforts have been made by scientists to enhance photocatalytic activities of SC photocatalyst through various means by modification of physiochemical properties of the nanomaterial. The modification can be done via doping (with metals, nonmetals, and salts), defect engineering, heterostructure, and cocatalysts [29, 30, 31]. Research has shown that doping greatly affects the electronic structure of SC nanomaterial [32]. Like TBP, the majority of SC photocatalysts have wide band-gaps energy, which makes it difficult for them to have photocatalytic activation with a visible light source [33, 34]. To improve the efficiency and quantum yield of SC photocatalysts such as TBP, their optical band-gap energy should be altered to respond to visible light sources. Another parameter that affects the photocatalytic activities of this material is presence of defects. Defects seen in a material can be artificial or natural specific structure. Surface defects alter geometric structure, as well as the chemical environment of the host material [35]. It can also serve as charge carrier traps and adsorption sites; the induced electrons can be transferred to the sites and, therefore, prevent recombination of photogenerated e—h+ pairs.
This chapter highlighted fundamental principles and mechanisms of SC photocatalysis and recent synthesis techniques that have been deployed in preparing TBP nanomaterial. The influence of reaction conditions and approaches such as doping, codoping, composites, temperature, pH, precursor type, surface area, and morphology on surface defects and optical band-gap energy of TBP nanomaterial was noted. Ultimately, impact of surface defects and optical properties of TBP on its photocatalytic activities against organic pollutants was discussed. Considering progress recorded so far in this area, some perspectives on how to advance and improve degradation efficiency of TBP against organic pollutants were proposed.
1.1 Fundamental principles and mechanisms of photocatalysis
Generally, photocatalysis is initiated when a SC photocatalyst absorbs photons with energy equal to or higher than its optical band-gap energy. Consequently, electrons in the valence band (VB) are excited into the conduction band (CB) leaving holes in the VB. This excitation produces a potential difference midway CB and VB bands, creating reductive and oxidative entities at the CB and VB, respectively. These photo-activated charge carriers can react with H2O or dissolved oxygen to generate free radicals such as OH and O−2 that can degrade pollutants into smaller molecules [36] as shown in Eqs. (1)–(6). It is fundamental that the minimum material CB is located at a higher negative potential compared to the reduction potential for H+ to H2, at the same time, it is also essential that the highest VB is located at a higher positive potential compared to the oxidation potential for H2O to O2 [22]. Figure 1 describes the indirect organic pollutant degradation process by SC photocatalyst.
Figure 1.
Pictorial description of indirect organic pollutant degradation process by SC photocatalyst. Adapted with permission [37].
SC+hv→eCB−+hVB+E1
hVB++H2O→∙OH+H+E2
hVB++∙OH−→∙OHadE3
eCB−+O2→∙O2_E4
∙OH+pollutants→CO2,H2O,saltsE5
∙OHad→∙OHfree+pollutant→simple oxid.productE6
1.2 Crystal structure of a perovskites
Perovskite material is generally referred to as material whose crystal structure is described by the formula ABO3, A and B are ions that often have different sizes and O is an ion that is bonded to A and B. It has a cubic structure that contains B cations in a 6-fold orientation encircled by an octahedral of anion while the A cation in a 12-fold cuboctahedral orientation [38]. Figure 2aandb describes the idealized cubic perovskite structure. From the crystal structure, B site cations are firmly glued to the oxygen (or other anion) at the same time A site cations interaction with the oxygen is relatively weaker. Based on the nature of the cations residing in the lattice sites, various perovskite crystal geometries can be obtained by modifying these interactions.
Figure 2.
(a and b) Crystal structure of a perovskite. Adapted from [39], copyright Springer Nature, 2019.
2. Synthesis techniques deployed in preparation of titanate-based perovskites nanomaterial
Various synthesis methods have been successfully deployed in the formulation of TBP nanomaterial. Surface defects and optical band-gap energy of TBP can be manipulated by deploying appropriate synthesis methods, which include the temperature, pH of the reaction, types of precursor, and solvents. In this section, we summarized recent methods deployed in synthesizes of TBP in Table 1 including the precursors used, reaction conditions, and pollutant/application.
3. Impact of surface defects and optical band-gap energy on photocatalytic activities of titanate-based perovskite nanomaterial
In recent times, substantial work has been done to enhance the physiochemical properties of TBP nanomaterial, more especially surface defects and band-gap energy. This is because of their role in the photocatalytic activities of this group of perovskites. Attempts have been made to modify these two parameters via reaction conditions and synthesis techniques. In this section, the role of reaction conditions on these physiochemical properties was highlighted. The impact of surface defects and band-gap energy on photocatalytic activities of TBP nanomaterial was also discussed.
Zhuang and co [43] reported three different morphologies of CaTiO3 formulated from three different Ti precursors through hydrothermal techniques for removal of As(III). After 40 mins of exposure to UV source, CaTiO3 sample with (Ti(OC3H7)4) (TIP) as a precursor showed the highest activities (98.4%) in removal of As(III). Figure 3 indicates the induced changes in the concentration of the As(III) under UV source against different morphologies of CaTiO3. The higher photocatalytic activity of CaTiO3 (TIP) was associated with its fern-like morphology and the higher specific area (108.142/g) when compared to other two.
Figure 3.
The induced changes in the concentration of the As(III) under UV-254 nm for different morphologies of CaTiO (A) CaTiO3 TTC (B) CaTiO3 TNB (C) CaTiO3 TIP and (D) No photocatalyst. Reprinted with permission from [43].
Cai et al. [44] fabricated surface disordered CaTiO3 using modified hydrogenation method. The as-prepared samples were utilized as a model to study roles of surface oxygen vacancies (SOVs) on photocatalytic H2 evolution under a visible light source. They demonstrated that CaTiO3 hydrogenated at 700°C induced more SOVs with a very high photocatalytic H2 evolution rate (2.96 mmol g−1 h−1). A value that is almost 49 times greater than the value of the pristine CaTiO3 without SOVs. They suggested that the significant increase in H2 production in the hydrogenated samples was because of the induced SOVs, which lower surface recombination of photogenerated e-h pair and increase charge separation.
Portia et al. [46] studied the influence of annealing temperature on photocatalytic activity of CaTiO3 NPs under the visible light source. The samples were prepared via sol–gel method and were annealed at various temperatures of 500°C, 700°C, and 900°C. The photocatalytic activities of the samples were assessed against MO and Rhb dyes. The sample annealed at 900°C exhibited the highest degradation efficiency (DE) 88% and 78% for Mo and Rhb, respectively, while sample annealed at 500°C showed DE of 53% and 38% for Mo and Rhb, respectively. The photocatalytic activity results also correlate with the result of UV–visible diffuse reflectance spectroscopy, which indicates the absorption of the sample annealed at 500°C to be 340 nm while the sample annealed at 900°C exhibited outstanding and improved visible—absorption with its peaks at 450 nm. The kinetic fit of the samples against MO and RhB dyes were shown in Figure 4. They associated the enhancement in photocatalytic activities of the sample annealed at 900°C to a decrease in the optical band-gap energy of the CaTiO3 sample, specific surface area with porous features as well as a low recombination rate of the e—h+ pairs.
Figure 4.
The kinetic fit of the samples against MO and RhB dyes exposed to a visible light source. Reprinted with permission [46].
Lazono-Sánchez et al. [47] reported influence of Eu3+ doping and heat treatment on photocatalytic activities of CaTiO3 under visible and near-infrared light sources. The results showed that samples doped with 1% Er3+ exhibited the highest degradation reaction rate against MB (4.54 × 10−5 s−1), a value, which is about 2.5 times higher than that of undoped sample 1.86 × 10−5 s−1. Furthermore, the as-prepared samples were calcined at 850°C and their photocatalytic activity against MB was also evaluated under UV–vis–NIR irradiation. They reported a significant increase in the photodegradation reaction rate of the calcined sample against MB. The author attributed improvement in the photocatalytic reaction rate of the samples to introducing a new energy state in the optical band-gap of the CaTiO3 and increased crystallinity. In another work, Yang et al. [48] reported photodegradation of MB by Fe-doped CaTiO3 under UV–visible light irradiation. They found that doping CaTiO3 with Fe enhanced its photocatalytic activity against MB. Nevertheless, the photocatalytic activities of Fe doped CaTiO3 sample calcined at a high temperature of 500°C exhibited higher activity of about 100%. Yang et al. associated enhancement in the light absorption of Fe doped CaTiO3 in the visible region with the high calcination temperature.
Recently, Chen et al. [45] reported Na + codoped CaTiO3:Eu3+ fabricated via solution combustion method using stoichiometric ratio of Ca1−xTiO3:Eu3+x (x = 0, 0.005, 0.01, 0.015, 0.02, and 0.025). The photocatalytic activity of the samples was evaluated against MB under UV light source. Figure 5(a, b, and c) indicates the Ca1-xTiO3:Eu3+x degradation of MB, kinetics plots of photocatalytic degradation, and first-order apparent rate constants (k) in photodegradation of MB. They recorded significant improvement in the photocatalytic activity of CaTiO3 after being doped with Eu3+. The CaTiO3 sample doped with 5% Eu3+ exhibited the highest DE relative to other samples, which the author attributed to the smaller optical band-gap energy of the sample relative to other samples. They also noted that Eu3+ doping led to a decrease in particle size of CaTiO3 hence enhancing its light absorption potential.
Figure 5.
Ca1−xTiO3:Eu3+x samples degradation of MB under UV light. (b) Ca1−xTiO3:Eu3+x kinetics plots of photocatalytic degradation of MB (c) Ca1−xTiO3:Eu3+x first-order apparent rate constants (k) in photodegradation of MB Reprinted with permission [45].
Bhat et al. [50] reported the influence of Rh occupying sites in BaTiO3 electronic structure. The samples were prepared by one-pot hydrothermal method and photocatalytic activities of the samples were evaluated against MB under visible light source. In the experiment, the authors found that samples doped with Rh exhibited higher photocatalytic activities than the pristine sample; with 0.5 Rh doped BaTiO3 having the highest photodegradation against MB. They attributed enhancement noted in Rh doped sample to a decrease in band-gap energy. Figure 6(a and b) describes the photocatalytic of the sample against MB and the rate constants (K) of pristine BaTiO3 and Rh-doped BaTiO3 against MB. The DFT studies also predicted that an increase in Rh concentration causes a decrease in the optical band-gap energy of the samples, which further increases the absorption light of the sample within the visible region.
Figure 6.
(a) The photocatalytic degradation of MB and (b) the rate constants (K) of the pristine BaTiO3 and Rh-doped BaTiO3 against MB. Reprinted with permission [50].
Similarly, Khan and co [52] reported effects of 1, 3, and 5% Ag doping on the optical properties and photocatalytic activities of BaTiO3 against Rhb dye under visible light illumination. The decomposition efficiency of BaTiO3, 1, 3, and 5% Ag doped BaTiO3 NPs are 41, 46, 58, and 79%, respectively, as indicated in Figure 7. The linear increase in photocatalytic activities of BaTiO3 was credited to the observed decrease in band-gap energy of BaTiO3 NPs as Ag concentration is increased as well as the decrease in the e—h+ recombination rate.
Figure 7.
Decomposition efficiency of the as-prepared samples against Rh B dye under visible light Illumination. Reprinted with permission [52].
Nishioka and Maeda [51] investigated H2 evolution of Rh doped BaTiO3 nanocrystal synthesized via the hydrothermal method with different precursors. The H2 evolution was evaluated using aqueous ethanol at wavelength of >420 nm. They claimed that H2 evolution via photocatalytic reaction of the samples depends strongly on the following; preferred TiO2 and Rh precursor, precursor ratio, and postheating process. A sample that consists of anatase NPs as its main phase indicated higher photocatalytic activity than sample with rutile precursor. They attributed improved photocatalytic activities of post-treated Rh doped BaTiO3 to higher temperature treatment.
Lu et al. [40] explored the effect of optical and structural properties of SrTiO3-BiFeO3 solid solution on its photocatalytic H2 production. The as-prepared sample was prepared via solid-state method using stoichiometric ratio as Sr1−xBixTi1−xFexO3 (0 ≤ x ≤ 0.4). The photocatalytic activities of the samples were studied by investigating hydrogen production from Na2SO3 (aq) solution under visible light illumination. At wavelength (≥250 nm), an obvious increase in H2 production was noted in the solid solution relative to pristine SiTiO3. The highest activity was noted in Sr0.9Bi0.1Ti0.9Fe0.1O3 sample with mean H2 production rate of 180 mol/h. This value corresponds to apparent quantum efficiency of 2.28% while pristine SrTiO3 H2 production activity rate was 17 mol/h. The pristine SrTiO3 value is one order of magnitude lower than that of the solid solution as shown in Figure 8. The authors attributed the higher activity rate of a solid solution to the observed larger surface area, which in turn creates more surface reaction sites at the surface. In addition, SrTiO3 indicated a distinct absorption edge in the UV region while the solid solution indicated a large absorption shoulder in the visible light region, which they link to metal-to-metal charge transfer.
Figure 8.
Photocatalytic H2 production of the samples when exposed to UV and visible light sources. Reprinted with permission [40] Copyright Elsevier 2017.
He et al. [41] reported photocatalytic activities of SrTiO3/reduced graphene oxide (SrTiO3-RGO) composites, prepared through a one-pot hydrothermal process. The as-prepared sample SrTiO3–0.8%RGO composites exhibited a considerable increase in photocatalytic production of H2 (363.79 mmol (g h)−1) than SrTiO3 under UV light exposure. The higher H2 production rate observed in the composite sample was associated with generation of more reactive sites and low recombination rate of the e—h+ caused by a suitable amount of RGO composition in SrTiO3. Moreover, the photoelectrochemical and electrochemical impedance spectroscopy analyses as shown in Figure 9(a and b) revealed that SrTiO3–0.8%RGO had higher photocurrent and lower impedance value than SrTiO3. This is an indication of enhanced charge transport, separation of the photo-generated electrons, and holes in the composite sample.
Figure 9.
Photocatalytic H2 production and (b) photoelectrochemical spectroscopy results of the samples. Reprinted with permission [41].
Pei et al. [49] formulated network-like hierarchical nanosized CaTiO3 via one-pot hydrothermal method and polyvinyl alcohol (PVA) as a structure guiding agent. The synthesized sample photocatalytic H2 evolution was evaluated under visible light illumination (>400 nm). It was noted that sample synthesized with PVA had a smaller band-gap value of 2.57 V compared to band-gap of sample synthesized without PVA at 3.55 eV, a value which is typical optical band-gap energy of perovskite CaTiO3. Under visible irradiation PVA-CaTiO3 H2 generation rate was 14.19 mol h−1 g−1 while CaTiO3 alone indicated a negligible H2 generation rate. The H2 generation rate of the samples is shown in Figure 10(i and ii). The authors ascribed the improvement in H2 generation by PVA-CaTiO3 to presence of defects such as oxygen vacancies (Vo). They found out that Vo creates an energy level at 0.95 eV below the CB, acted as e− donor, and aided charge transport and separation.
Figure 10.
(i) Depicts the H2 generation rate of PVA-CaTiO3 and pristine CaTiO3 Reprinted with permission [49].
Abirami et al. [53] synthesized undoped PbTiO3 and 0.01, 0.02, and 0.03% Ag–Fe codoped PbTiO3 NPs via hydrothermal method. The photocatalytic activities of the as-prepared samples were evaluated using MB dyes under UV light source. The results showed that 0.02% Ag-Fe codoped PbTiO3 exhibited the highest photocatalytic decoloration of MB (80.4%) at pH 0f 6 within 2 h. From Figure 11, it appears that pH also played a critical role in photodegradation of MB; the higher the pH value, the better the discolorization efficiency. According to Devi et al. [56], the adsorption of dyes on SC photocatalysts relies on pH as a result of the changes in the point zero charge of a SC photocatalyst at different pH. The author’s associated improvement in the decolorization to reduction in e—h+ recombination rate caused by trapping photo-excited electrons by Ag and Fe.
Figure 11.
The decolorization efficiency of the sample at the different pH a) at pH of 2. B) at pH of 4, and c) at pH of 6 Reprinted with permission [53].
Pirgholi-Givi et al. [54] studied the influence of the synthesis methods on photocatalytic activities of mixed BiTi3O12 and Bi12TiO20 NPs. The samples were formulated via microwave-assisted (S1) and hydrothermal synthesis (S2) methods. Their findings revealed that photocatalytic activity of the S1-sample was about 1.4 times higher than S2-sample at a higher pH value (12.5); S1-sample degraded 98% of MB in 28 min while S2-sample degraded 98% of MB in 40 min. The presence of Bi12Ti12O20 phase in Bi4Ti3O12 substrates elevated charge carrier span, enhanced charge separation, and photodegradation of the MB. Figure 12 shows a decline in percentage of degradation of the test dye.
Figure 12.
Photocatalytic activities of S1- sample and S2-sample against MB. Reprinted with permission [54].
Use of titanante-based perovskite nanomaterial in photocatalytic application seems to be a promising and effective approach to mitigate the challenges that are associated with water pollution. However, considerable numbers of TBP have large optical band-gap energy, which allows photocatalytic reaction only with a UV source. In addition, the majority of TBP have excellent photocatalytic ability but with a high rate of recombination of the photogenerated e-h+ pair which significantly affects its efficiency. Some of these challenges made scientists explore ways to optimize and improve photocatalytic activities of TBP material.
In this chapter, we made efforts to avail the overview of basic principles and mechanisms of an SC photocatalyst and recent synthesis techniques that have been deployed in preparing TBP nanomaterial. Special effort was made to highlight the influence of reaction conditions and approaches such as doping, codoping, composites, temperature, and pH on the surface defects and optical properties of TBP nanomaterial. Particularly, how surface effects and optical properties of these materials impact their photocatalytic activities were also discussed. Finally, the future perspective of TBP was proposed in the chapter.
Deploying appropriate synthesis methods and precursors is quite essential as it creates room to control the particle size, crystal structure, shapes, and morphology of a TBP photocatalyst. These physiochemical parameters play a vital role in modification of the electronic bandgap and surface defects of TBP photocatalysts. Much effort should be made to adopt appropriate methods and control over physiochemical properties of these group SC photocatalysts. Attention should also be given to reaction conditions such as temperature and pH of the system during synthesis. Regulating pH and annealing temperature have shown improved crystallinity of TBP, which in turn aids its photocatalytic activities under visible light irradiation. Other strategies that have been efficient in improving photocatalytic activities of TBP material include doping, codoping, and composites with nonmetal, metals, and perovskites material. These strategies have shown to increase charge carrier span, reactive sites, surface oxygen vacancies, decrease in bandgaps, and recombination rate of photogenerated e−- h+ pair, improve charge separation, and photocatalytic absorption in the visible light region.
In spite of the progress made in recent times in understanding reaction processes and path involved in degradation of organic wastes and the role of doping TBP with other elements or TBP composite plays in altering its optical band-gap. Nevertheless, the sturdiness of these materials over time and their catalytic active cores require more detailed explanation. Hence there is a need to advance more accurate density-functional models to help optimize the photocatalytic configurations of these materials. In addition, more work should be done to optimize the reaction conditions of TBP nanomaterial, especially pH and temperature selection. Appropriate control to both parameters can enhance its photocatalytic activities as demonstrated by few authors. More work should be done to study photocorrosion of titanate-based perovskite nanomaterial.
We thank Engr. Emeka Okwuosa for the generous sponsorship of April 2014, July 2016, July 2018, and July 2021 conferences/workshops on applications of nanotechnology to Energy, Health and Environment, and for providing some research facilities.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
References
1.Rana RS, Singh P, Kandari V, Singh R, Dobhal R, Gupta S. A review on characterization and bioremediation of pharmaceutical industries’ wastewater: An Indian perspective. Applied Water Science. 2017;7:1-12
2.Palmate SS, Pandey A, Kumar D, Pandey RP, Mishra SK. Climate change impact on forest cover and vegetation in Betwa Basin, India. Applied Water Science. 2017;7:1-12
3.Adeogun AO, Ibor OR, Adeduntan SD, Arukwe A. Intersex and alterations in the reproductive development of cichlid, Tilapia Guineensis, from a municipal domestic water supply lake (Eleyele) in south western Nigeria. Science of the Total Environment. 2016;541:372-382
4.Jung C, Son A, Her N, Zoh K, Cho J, Yoon Y. Removal of endocrine disrupting compounds, pharmaceuticals, and personal care products in water using carbon nanotubes: A review. Journal of Industrial and Engineering Chemistry. 2015;27:1-11
5.Inyinbor AA, Adekola FA, Olatunji GA. Liquid phase adsorption of Rhodamine B onto acid treated Raphia hookerie epicarp: Kinetics, isotherm and thermodynamics studies. South African Journal of Chemistry. 2016;69:218-226
6.Kumar A, Kumar S, Krishnan V. Perovskite-Based Materials for Photocatalytic Environmental Remediation. Inamuddin et al. (eds.), Nanophotocatalysis and Environmental Applications, Environmental Chemistry for a Sustainable World. Springer Nature Switzerland AG; 2019 29, DOI: 10.1007/978-3-030-10609-6_5
7.Nkwachukwu OV, Arotiba OA. Perovskite oxide–based materials for photocatalytic and photoelectrocatalytic treatment of water. Frontiers in Chemistry. 2021;9:634630. DOI: 10.3389/fchem.2021.634630
8.Okeke IS, Agwu KK, Ubachukwu AA, et al. Impact of Cu doping on ZnO nanoparticles phyto-chemically synthesized for improved antibacterial and photocatalytic activities. Journal of Nanoparticle Research. 2020:22. DOI: 10.1007/s11051-020-04996-3
9.Manvendra P, Rahul K, Kamal K, Todd M, Charles UP Jr, Dinesh M. Pharmaceuticals of emerging concern in aquatic systems: Chemistry, occurrence, effects, and removal methods. Chemical Reviews. 2019;119:3510-3673
10.Marta M, Jolanta K, Iseult L, Marianne M, Jan K, Steve B, et al. Changing environments and biomolecule coronas: Consequences and challenges for the design of environmentally acceptable engineered nanoparticles. Green Chemistry. 2018;20:4133-4168
11.Wenya H, Kelong A, Xiaoyan R, Shengyan W, Lehui L. Inorganic layered ion-exchangers for decontamination of toxic metal ions in aquatic systems. Journal of Materials Chemistry A. 2017;5:19593-19606
12.Manolis JM, Mercouri GK. Metal sulfide ion exchangers: Superior sorbents for the capture of toxic and nuclear waste-related metal ions. Chemical Science. 2016;7:4804-4824
13.Okeke IS, Agwu KK, Ubachukwu AA, Madiba IG, Maaza M, Whyte GM, et al. Impact of particle size and surface defects on antibacterial and photocatalytic activities of undoped and Mg-doped ZnO nanoparticles, biosynthesized using one-step simple process. Vacuum. 2021;187:110110. DOI: 10.1016/j.vacuum.2021.110110
14.Wanjun WYY, Taicheng A, Guiying L, Ho YY, Jimmy CY, Po KW. Visible-light-driven photocatalytic inactivation of E. coli K-12 by bismuth vanadate nanotubes: bactericidal performance and mechanism. Environmental Science & Technology. 2012;46:4599-4606
15.Nadine C, Stefanie I, Elisabeth S, Marjan V, Karolin K, David D, et al. Inactivation of antibiotic resistant bacteria and resistance genes by ozone: From laboratory experiments to full-scale wastewater treatment. Environmental Science & Technology. 2016;50:11862-11871
16.Chen J, Dong C, Idriss H, Mohammed OF, Bakr OM. Metal halide Perovskites for solar-to-chemical fuel conversion. Advanced Energy Materials. 2020;10:1902433
17.He F, Wang ZX, Li YX, Peng SQ, Liu B. The nonmetal modulation of composition and morphology of g-C3N4-based photocatalysts. Applied Catalysis B: Environmental. 2020;269:118828
18.Nie L, zhang q. Recent Progress on crystalline metal chalcogenides as efficient photocatalysts for organic pollutants degradation. Inorganic Chemistry Frontiers. 2017;4:1953-1962
19.Akyüz D, Zunain Ayaz RM, Yılmaz S, et al. Metal chalcogenide based photocatalysts decorated with heteroatom doped reduced graphene oxide for photocatalytic and photoelectrochemical hydrogen production. International Journal of Hydrogen Energy. 2019;44:18836-18847
20.Lacorre P, Goutenoire F, Bohnke O, Retoux R, Laligant Y. Designing fast oxide-ion conductors based on La2Mo2O9. Nature. 2000;404:856-858. DOI: 10.1038/35009069
21.Shimizu T. Partial oxidation of hydrocarbons and oxygenated compounds on perovskite oxides. Catalysis Reviews. 1992;34:355-371. DOI: 10.1080/01614949208016317
22.Asri M, Adnan B, Arifin K, Minggu LJ, Kassim MB. Titanate-based perovskites for photochemical and photoelectrochemical water splitting applications: A review. International Journal of Hydrogen Energy. 2018;43:23209-23220
23.Xu Y, Schoonen MAA. The absolute energy positions of conduction and valence bands of selected semiconducting minerals. American Mineralogist. 2000;85:543e56
24.Kanhere P, Chen Z. A review on visible light active perovskite-based photocatalysts. Molecules. 2014;19:19995e20022
25.Wang L, Yang G, Peng S, Wang J, Ji D, Yan W, et al. Fabrication of MgTiO3 nanofibers by electrospinning and their photocatalytic water splitting activity. International Journal of Hydrogen Energy. 2017;42:25882e90
26.Qu Y, Zhou W, Fu H. Porous cobalt titanate nanorod: A new candidate for visible light-driven photocatalytic water oxidation. Chem Cat Chem. 2013;6:265e70
27.Qu Y, Zhou W, Ren Z, Du S, Meng X, Tian G, et al. Facile preparation of porous NiTiO3 nanorods with enhanced visible-light-driven photocatalytic performance. Journal of Materials Chemistry. 2012;22:16471e6
28.Sierra GG, Mari’n Alzate N, Arnache O. A novel LaFeO3XNX oxynitride. Synthesis and characterization. Journal of Alloys and Compounds. 2013;549:163e9
29.Ma L, Li N, Wu G, Song G, Li X, Han P, et al. Interfacial enhancement of carbon fiber composites by growing TiO2 nanowires onto amine based functionalized carbon fiber surface in supercritical water. Applied Surface Science. 2018;433:560-567. DOI: 10.1016/j.apsusc.2017.10.036
30.Zhang L, Yu W, Han C, Guo J, Zhang Q, Xie J, et al. Large scaled synthesis of heterostructured electrospun TiO2/SnO2 nanofibers with an enhanced photocatalytic activity. Journal of the Electrochemical Society. 2017;164:H651-H656. DOI: 10.1149/2.1531709jes
31.Zhang L, Qin M, Yu W, Zhang Q, Xie H, et al. Heterostructured TiO2/WO3 nanocomposites for photocatalytic degradation of toluene under visible light. Journal of the Electrochemical Society. 2017;164:H1086-H1090. DOI: 10.1149/2.0881714jes
32.Shenoy S, Bhat DK. Enhanced bulk thermoelectric performance of Pb0.6Sn0.4Te: Effect of magnesium doping. Journal of Physical Chemistry C. 2017;121:20696-20703
33.Parkinson B. An overview of the progress in photoelectrochemical energyconversion. Journal of Chemical Education. 1960;60:338-340
34.Osterloh FE. Inorganic materials as catalysts for photochemical splitting ofwater. Chemistry of Materials. 2008;20:35-54
35.Bai S, Zhang N, Gao C, Y. Xiong defect engineering in photocatalytic materials. Nano Energy. 2018;52:296-336
36.Ajmal A, Majeed I, Malik RN, Idriss H, Nadeem MA. Principles and mechanisms of photocatalytic dye degradation on TiO based photocatalysts: a comparative overview. RSC Advances. 2014;4:37003-37026. DOI: 10.1039/C4RA06658H
37.Rauf MA, Ashraf SS. Fundamental principles and application of heterogeneous photocatalytic degradation of dyes in solution. Chemical Engineering Journal. 2009;151:10-18. DOI: 10.1016/j.cej.2009.02.026
38.Orlovskaya N, Browning N. Mixed Ionic Electronic Conducting Perovskites for Advanced Energy Systems. Springer Dordrecht; 2004. p. 314. DOI: 10.1007/978-1-4020-2349-1
39.Gao L, Guan Z, Huang S, Liang K, ChenH ZJ. Enhanced dielectric properties of barium strontium titanate thin films by doping modification. Journal of Materials Science: Materials in Electronics. 2019;30:12821-12839
40.Lu L, Lv M, Liu G, Xu X. Photocatalytic hydrogen production over solid solutions between BiFeO3 and SrTiO3. Applied Surface Science. 2017;391:535-541. DOI: 10.1016/j.apsusc.2016.06.160
41.He G, Zhong Y, Chen M, Li X, Fang Y, Xu Y. One-pot hydrothermal synthesis of SrTiO3-reduced graphene oxide composites with enhanced photocatalytic activity for hydrogen production. Journal of Molecular Catalysis A: Chemical. 2016;423:70-76. DOI: 10.1016/j.molcata.2016.05.025
42.Zhang H, Chen G, Li Y, Teng Y. Electronic structure and photocatalytic properties of copper-doped CaTiO3. International Journal of Hydrogen Energy. 2010;35:2713-2716. DOI: 10.1016/j.ijhydene.2009.04.050
43.Zhuang J, Tian Q, Lin S, Yang W, Chen L, Liu P. Precursor morphology-controlled formation of perovskites CaTiO3 and their photo-activity for As(III) removal. Applied Catalysis B: Environmental. 2014:108-115. DOI: 10.1016/j.apcatb.2014.02.015
44.Cai J, Cao A, Huang J, Jin W, Zhang J, Jiang Z, et al. Understanding oxygen vacancies in disorder-engineered surface and subsurface of CaTiO3 nanosheets on photocatalytic hydrogen evolution. Applied Catalysis B: Environmental. 2020;267:118378. DOI: 10.1016/j.apcatb.2019.118378
45.Chen M, Xiong Q, Liua Z, Qiu K, Xiao X. Synthesis and photocatalytic activity of Na+ co-doped CaTiO3:Eu3+ photocatalysts for methylene blue degradation. Ceramics International. 2020;46:12111-12119
46.Portia SAU, Rajkumar S, Elanthamilan E, Merlin JP, Ramamoorthy K. Effect of annealing temperature on structural, optical and visible light photocatalytic performance of CaTiO3 catalysts synthesized by simple solgel technique. Inorganic Chemistry Communications. 2020;119:108051
47.Lozano-Sáncheza LM, Obregón S, Díaz-Torres LA, Lee S, Rodríguez-González V. Visible and near-infrared light-driven photocatalytic activity oferbium-doped CaTiO3 system. Journal of Molecular Catalysis A: Chemical. 2015;410:19-25
48.Yang H, Han C, Xue X. Photocatalytic activity of Fe-doped CaTiO3 under UV–visible light.Journal of environmental. Sciences. 2014;26:1489-1495. DOI: 10.1016/j.jes.2014.05.015
49.Pei J, Meng J, Wu S, Lin Q, Li J, Wei X, et al. Hierarchical CaTiO3 nanowire-network architectures for H2 evolution under visible-light irradiation. Journal of Alloys and Compounds. 2019;806:889e896
51.Nishioka S, Maeda K. Hydrothermal synthesis of Rhodium-doped barium titanate nanocrystals for enhanced photocatalytic hydrogen evolution under visible light. RSC Advances. 2015;5:100123. DOI: 10.1039/c5ra20044j
52.Khan MAM, Kumar S, Ahmed JC, Ahamed M, Kumar A. Influence of silver doping on the structure, optical and photocatalytic properties of Ag-doped BaTiO3 ceramics. Materials Chemistry and Physics. 2021;259:124058
53.Abirami R, Senthil TS, Kalaiselvi CR. Preparation of pure PbTiO3 and (Ag–Fe) codoped PbTiO3 perovskite nanoparticles and their enhanced photocatalytic activity. Solid State Communications. 2021;327:114232. DOI: 10.1016/j.ssc.2021.114232
54.Pirgholi-Givia G, Farjami-Shayesteha S, Azizian-Kalandaragh Y. The influence of preparation parameters on the photocatalytic performance of mixed bismuth titanate-based nanostructures. Physica B: Condensed Matter. 2019;575:311572. DOI: 10.1016/j.physb.2019.07.007
55.Yang Z, Fan H, Wang X, Long C. Rapid microwave-assisted hydrothermal synthesis of Bi12TiO20 hierarchica larchitecture with enhanced visible-light photocatalytic activities. Journal of Physics and Chemistry of Solids. 2013;74:1739-1744. DOI: 10.1016/j.jpcs.2013.06.020
56.Devi LG. Reddy KM Enhanced photocatalytic activity of silver metallized TiO2 particles in the degradation of an azo dye methyl orange: Characterization and activity at different pH values. Applied Surface Science. 2010;256:3116-3121
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