Metal oxides as photocatalysts

AbstractMetal oxides are of great technological importance in environmental remediation and electronics because of their capability to generate charge carriers when stimulated with required amount of energy. The promising arrangement of electronic structure, light absorption properties, and charge transport characteristics of most of the metal oxides has made possible its application as photocatalyst. In this article definition of metal oxides as photocatalyst, structural characteristics, requirements of the photocatalyst, classification of photocatalysts and the mechanism of the photocatalytic process are discussed

Metal oxides as photocatalysts

Metal oxides are of great technological importance in environmental remediation and electronics because of their capability to generate charge carriers when stimulated with required amount of energy. The promising arrangement of electronic structure, light absorption properties, and charge transport characteristics of most of the metal oxides has made possible its application as photocatalyst. In this article definition of metal oxides as photocatalyst, structural characteristics, requirements of the photocatalyst, classification of photocatalysts and the mechanism of the photocatalytic process are discussed

Environmentally Sustainable Fabrication of Ag@g‑C3N4 Nanostructures and Their Multifunctional Efficacy as Antibacterial Agents and Photocatalysts

<div>Noble-metal silver (Ag) nanoparticles (NPs) anchored/decorated onto polymeric graphitic carbon nitride (g-C3N4) as nanostructures (NSs) were prepared using</div><div>modest and environment-friendly synthesis method with a developed-single-strain biofilm as a reducing implement. The as-fabricated NSs were characterized using standard</div><div>characterization techniques. The nanosized and uniform AgNPs were well deposited onto the sheet-like matrix of g-C3N4 and exhibited good antimicrobial activity and superior</div><div>photodegradation of dyes methylene blue (MB) and rhodamine B (RhB) dyes under visible-light illumination. The Ag@g-C3N4 NSs exhibited active and effective bactericidal</div><div>performance and a survival test in counter to Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The as-fabricated NSs also exhibited superior visible-light</div><div>photodegradation of MB and RhB in much less time as compared to other reports. Ag@g-C3N4 NSs (3 mM) showed superior photocatalytic measurements under visible-light irradiation: ∼100% MB degradation and ∼89% of RhB degradation in 210 and 250 min, respectively. The obtained results indicate that the AgNPs were well deposited onto the g-C3N4 structure, which decreases the charge recombination rate of photogenerated electrons and holes and extends the performance of pure g-C3N4 under visible light. In conclusion, the as-fabricated Ag@g-C3N4 NSs are keen nanostructured materials that can be applied as antimicrobial materials and visible-light-induced photocatalysts.</div

CdS-graphene Nanocomposite for Efficient Visible-light-driven Photocatalytic and Photoelectrochemical Applications

<div>This paper reports cadmium sulphide nanoparticles-(CdS NPs)-graphene nanocomposite (CdS-Graphene),</div><div>prepared by a simple method, in which CdS NPs were anchored/ decorated successfully onto graphene sheets. The as-synthesized nanocomposite was characterized using standard characterization techniques. A combination of CdS NPs with the optimal amount of two-dimensional graphene sheets had a profound influence on the properties of the resulting hybrid nanocomposite, such as enhanced optical, photocatalytic, and photo-electronic properties. The photocatalytic degradation ability of the CdS-Graphene nanocomposite was evaluated by degrading different types of dyes in the dark and under visible light irradiation. Furthermore, the photoelectrode performance of the nanocomposite was evaluated by different electrochemical techniques. The results showed that the CdS-Graphene nanocomposite can serve as an efficient visible-light-driven photocatalyst as well as photoelectrochemical performance for optoelectronic applications. The significantly enhanced photocatalytic and photoelectrochemical performance of the CdS-Graphene nanocomposite was attributed to the synergistic effects of the enhanced light absorption behaviour and high electron conductivity of the CdS NPs and graphene sheets, which facilitates charge separation and lengthens the lifetime of photogenerated electron–hole pairs by reducing the recombination rate. The as-synthesized narrow band gap CdS-Graphene nanocomposite can be used for wide range of visible light-induced photocatalytic and photoelectrochemical based applications.</div

Environmentally sustainable biogenic fabrication of AuNP decorated-graphitic g-C3N4 nanostructures towards improved photoelectrochemical performances

<div>Noble-metal gold (Au) nanoparticles (NPs) anchored/decorated on polymeric graphitic carbon nitride (g-</div><div>C3N4), as a nanostructure, was fabricated by a simple, single step, and an environmentally friendly</div><div>synthesis approach using single-strain-developed biofilm as a reducing tool. The well deposited/</div><div>anchored AuNPs on the sheet-like structure of g-C3N4 exhibited high photoelectrochemical</div><div>performance under visible-light irradiation. The Au-g-C3N4 nanostructures behaved as a plasmonic</div><div>material. The nanostructures were analyzed using standard characterization techniques. The effect of</div><div>AuNPs deposition on the photoelectrochemical performance of the Au-g-C3N4 nanostructures was</div><div>examined by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), incident</div><div>photon-to-current efficiency (IPCE) and cyclic voltammetry (CV) in the dark and under visible-light</div><div>irradiation. The optimal charge transfer resistance for Au-g-C3N4 nanostructures (6 mM) recorded at</div><div>18.21 1.00 U cm2 and high electron transfer efficiency, as determined by EIS. The improved</div><div>photoelectrochemical performance of the Au-g-C3N4 nanostructures was attributed to the synergistic</div><div>effects between the conduction band minimum of g-C3N4 and the plasmonic band of AuNPs, including</div><div>high optical absorption, uniform distribution, and nanoscale particle size. This simple, biogenic approach</div><div>opens up new ways of producing photoactive Au-g-C3N4 nanostructures for potential practical</div><div>applications, such as visible light-induced photonic materials for real device development.</div

Chalcogenides and Chalcogenide-Based Heterostructures as Photocatalysts for Water Splitting

Chalcogenides are essential in the conversion of solar energy into hydrogen fuel due to their narrow band gap energy. Hydrogen fuel could resolve future energy crises by substituting carbon fuels owing to zero-emission carbon-free gas and its eco-friendliness. The fabrication of different metal chalcogenide-based photocatalysts with enhanced photocatalytic water splitting have been summarized in this review. Different modifications of these chalcogenides, including coupling with another semiconductor, metal loading, and doping, are fabricated with different synthetic routes that can remarkably improve the photo-exciton separation and have been extensively investigated for photocatalytic hydrogen generation. In this direction, this review is undertaken to provide an overview of the enhanced photocatalytic performance of the binary and ternary chalcogenide heterostructures and their mechanisms for hydrogen production under irradiation of light

Biogenic Fabrication of Au@CeO2 Nanocomposite with Enhanced Visible Light Activity

<div>This study reports a biogenic approach to the synthesis of Au@CeO2 nanocomposite using electrochemically active biofilms (EABs) in water under normal pressure and 30°C. This work presents the results of extensive morphological, structural, optical, visible light photoelectrochemical and photocatalytic studies of Au@CeO2 nanocomposite. The presence of a large number of interfaces between Au nanoparticles and CeO2 for charge transfer is believed to play a key role in enhancing the optical and visible light photoelectrochemical and photocatalytic performance of Au@CeO2 nanocomposite. The enhanced visible light degradation of methyl orange and methylene blue by Au@CeO2 nanocomposite was much higher than that by pure CeO2. The reusability, stability, and other results suggests that the Au@CeO2 nanocomposite could be exploited as potential candidates for visible light photocatalysis, photovoltaic, and photoelectrochemical devices.</div

Ce3+-ion-induced visible-light photocatalytic degradation and electrochemical activity of ZnO/CeO2 nanocomposite

<div>In this study, pure ZnO, CeO2 and ZnO/CeO2 nanocomposites were synthesized using a thermal</div><div>decomposition method and subsequently characterized using different standard techniques. High resolution X-ray photoelectron spectroscopy measurements confirmed the oxidation states and presence of Zn2+, Ce4+, Ce3+ and different bonded oxygen species in the nanocomposites. The prepared pure ZnO and CeO2 as well as the ZnO/CeO2 nanocomposites with various proportions of ZnO and</div><div>CeO2 were tested for photocatalytic degradation of methyl orange, methylene blue and phenol under visible-light irradiation. The optimized and highly efficient ZnO/CeO2 (90:10) nanocomposite exhibited enhanced photocatalytic degradation performance for the degradation of methyl orange, methylene blue, and phenol as well as industrial textile effluent compared to ZnO, CeO2 and the other</div><div>investigated nanocomposites. Moreover, the recycling results demonstrate that the ZnO/CeO2 (90:10)</div><div>nanocomposite exhibited good stability and long-term durability. Furthermore, the prepared ZnO/CeO2</div><div>nanocomposites were used for the electrochemical detection of uric acid and ascorbic acid. The ZnO/CeO2 (90:10) nanocomposite also demonstrated the best detection, sensitivity and performance among the investigated materials in this application. These findings suggest that the synthesized ZnO/CeO2 (90:10) nanocomposite could be effectively used in various applications.</div