Journal of Materials Chemistry A Editor’s choice web collection: “Recent advances in solar fuels and photocatalysis research”
Frank E.
Osterloh
Department of Chemistry, University of California, Davis, CA 95616, USA. E-mail: fosterloh@ucdavis.edu
Abstract
Frank E. Osterloh introduces a Journal of Materials Chemistry A Editor’s choice web collection on recent advances in solar fuels and photocatalysis research (https://rsc.li/PhotoCat).
 Frank E. Osterloh |
Research on solar fuel generation and photocatalysis continues to attract strong interest in the community. Solar photons are free of cost and their energy can be used to generate sustainable fuels and help us mitigate the negative impact of society on the planet. That said, harvesting solar photons at Earth’s surface level and coaxing their energy content into technologically useful energy streams is no small feat. It requires materials that are strong light absorbers, that feature long excited state lifetimes, and that enable fast charge carrier extraction.
Photovoltaic cells can achieve these functions, and accordingly, they are expected to provide 16% of global electricity demand in 2050.1 The future of solar fuel generation is less predictable, as there exists considerable uncertainty about the best and most scalable device designs and processes (e.g. thermochemical versus excitonic). It is in this area where basic research on materials and catalysts will have its strongest impact. The same can be said about the future of photocatalysis. Because photocatalysts have a complementary function (in that they promote exergonic, not endergonic, fuel forming reactions), device and materials requirements are very different from those of solar fuel generators.2
In order to highlight developments in solar fuel generators and in photocatalysts, this online collection (https://rsc.li/PhotoCat) summarizes recent experimental papers and reviews published on the topic. The review ‘Nanostructured catalysts for electrochemical water splitting: current state and prospects’, by Xiumin Li and others surveys known electrocatalysts for water electrolysis, a pathway to hydrogen fuel (DOI: 10.1039/c6ta02334g). The review covers metal carbides, chalcogenides, phosphides, and oxides, and metal-free electrocatalysts. Certain electrode materials can serve as catalysts for both the hydrogen evolution and the oxygen evolution reaction. These systems are reviewed by Ya Yan and coworkers in ‘A review on noble-metal-free bifunctional heterogeneous catalysts for overall electrochemical water splitting’ (DOI: 10.1039/c6ta08075h). In their review ‘Two-dimensional nanosheets for electrocatalysis in energy generation and conversion’, Hengcong Tao and others focus on 2D nanomaterials that are electrocatalysts for the hydrogen evolution reaction, the oxygen evolution reaction, and for electrochemical CO2 reduction (DOI: 10.1039/c7ta00075h).
The collection also features a number of experimental papers. In ‘CoP2 nanoparticles on reduced graphene oxide sheets as a super-efficient bifunctional electrocatalyst for full water splitting’, Jianmei Wang et al. show that high surface area electrodes containing cobalt phosphide particles on reduced graphene oxide can split water at very low overpotentials (DOI: 10.1039/c6ta00596a). Similarly, in ‘Two-step synthesis of binary Ni–Fe sulfides supported on nickel foam as highly efficient electrocatalysts for the oxygen evolution reaction’, Bin Dong et al. demonstrate water electrolysis in alkaline pH using nickel iron sulfide electrocatalysts supported on nickel foam (DOI: 10.1039/c6ta03177c).
In ‘In situ confined synthesis of molybdenum oxide decorated nickel-iron alloy nanosheets from MoO42− intercalated layered double hydroxides for the oxygen evolution reaction’, Chao Xie et al. demonstrate that the incorporation of molybdenum oxide into nickel iron layered double hydroxides can produce active OER electrocatalysts (DOI: 10.1039/c6ta08149e). In ‘Controlled synthesis of Mo-doped Ni3S2 nano-rods: an efficient and stable electro-catalyst for water splitting’, Zheng Cui and coworkers describe a bi-functional catalyst for alkaline water electrolysis composed of molybdenum-doped nickel sulfide rods on nickel foam (DOI: 10.1039/c6ta09853c). In ‘High-performance urea electrolysis towards less energy-intensive electrochemical hydrogen production using a bifunctional catalyst electrode’, the concept of bi-functionality is extended to electrochemical urea oxidation, an electron source available from bio-waste streams (DOI: 10.1039/c6ta11127k). Proton reduction at low overpotential does actually not require any metals at all. This is shown by Dafeng Yan and others in ‘Electropolymerized supermolecule derived N, P co-doped carbon nanofiber networks as a highly efficient metal-free electrocatalyst for the hydrogen evolution reaction’ (DOI: 10.1039/c6ta05863a). Additionally, the oxygen reduction reaction is of interest for the design of fuel cells for the conversion of chemicals into electricity. In ‘High oxygen reduction activity on a metal–organic framework derived carbon combined with high degree of graphitization and pyridinic-N dopants’, Liangjun Li and coworkers show that porous conductors with high activity for ORR can be produced by partial decomposition of metal–organic framework materials (DOI: 10.1039/c6ta08016b).
Among photocatalyst materials, TiO2 continues to offer opportunities for research. In ‘Facile strategy for controllable synthesis of stable mesoporous black TiO2 hollow spheres with efficient solar-driven photocatalytic hydrogen evolution’, Weiyao Hu and others introduce a synthetic strategy for the production of hollow, hydrogen doped TiO2 spheres that can evolve hydrogen from solutions of sacrificial electron donors (DOI: 10.1039/c6ta01928e). The work showcases the importance of specific surface area for photocatalytic activity. In ‘Ni12P5 nanoparticles embedded into porous g-C3N4 nanosheets as a noble-metal-free hetero-structure photocatalyst for efficient H2 production under visible light’, Deqian Zeng et al. show that nickel phosphide proton reduction cocatalysts work well in combination with g-C3N4 photocatalysts (DOI: 10.1039/c7ta04816e).
A few years ago, carbon quantum dots emerged as a new class of materials. In ‘Recent progress in carbon quantum dots: synthesis, properties and applications in photocatalysis’, Ru Wang and coworkers survey methods of the synthesis, properties, and uses of carbon quantum dots for photocatalytic reactions (DOI: 10.1039/c6ta08660h). Lastly, in ‘MXene: a promising photocatalyst for water splitting’, Zhonglu Guo et al. use DFT methods to determine promising MXene structures as photocatalysts for the overall water splitting reaction (DOI: 10.1039/c6ta04414j).
These are just a few of the many papers published in Journal of Materials Chemistry A on the topic of photocatalysis and solar fuel generation. I hope that you will find them interesting!
Sincerely yours,
Frank Osterloh
References
- I. E. Agency, Technology Roadmap: Solar Photovoltaic Energy, 2014 Search PubMed.
- F. E. Osterloh, ACS Energy Lett., 2017, 445–453, DOI:10.1021/acsenergylett.6b00665.
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