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Electronic defects in metal oxide photocatalysts

Nature Reviews Materials volume 7, pages 503–521 (2022)Cite this article

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Abstract

A deep understanding of defects is essential for the optimization of materials for solar energy conversion. This is particularly true for metal oxide photo(electro)catalysts, which typically feature high concentrations of charged point defects that are electronically active. In photovoltaic materials, except for selected dopants, defects are considered detrimental and should be eliminated to minimize charge recombination. However, photocatalysis is a more complex process in which defects can have an active role, such as in stabilizing charge separation and in mediating rate-limiting catalytic steps. In this Review, we examine the behaviour of electronic defects in metal oxides, paying special attention to the principles that underpin the formation and function of trapped charges in the form of polarons. We focus on how defects alter the electronic structure of metal oxides, statically or transiently upon illumination, and discuss the implications of such changes in light-driven catalytic reactions. Finally, we compare oxide defect chemistry with that of new photocatalysts based on carbon nitrides, polymers and metal halide perovskites.

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Fig. 1: Point defects in a metal oxide.
Fig. 2: Polaron chemistry.
Fig. 3: Fundamental steps in photocatalysis.
Fig. 4: Role of defects in solid–liquid equilibration, light absorption and charge transport.
Fig. 5: Impact of charge localization on defects and polarons.
Fig. 6: Role of defects in surface catalysis.

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Acknowledgements

The authors thank L. Harnett for sharing his data and insights on WO3. E.P. acknowledges support from grant IJC2018-037384-I, funded by MCIN/AEI /10.13039/501100011033. S.S. and J.R.D. acknowledge funding from the European Union’s Horizon 2020 Research And Innovation Programme under grant agreements 884444-SUN2CHEM and 732840-A-LEAF. M.S. thanks the UK EPSRC for a Doctoral Prize Fellowship. A.A.B. is a Royal Society University Research Fellow. This work was partially funded by CEX2019-000910-S (MCIN/AEI/10.13039/501100011033), Fundació Cellex, Fundació Mir-Puig and Generalitat de Catalunya through CERCA.

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Authors and Affiliations

  1. ICFO (Institut de Ciències Fotòniques), The Barcelona Institute of Science and Technology, Castelldefels, Spain

    Ernest Pastor

  2. Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, UK

    Michael Sachs, Shababa Selim, James R. Durrant & Artem A. Bakulin

  3. Department of Materials, Imperial College London, London, UK

    Aron Walsh

  4. Department of Material Science and Engineering, Yonsei University, Seoul, Korea

    Aron Walsh

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  1. Ernest Pastor
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  2. Michael Sachs
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  3. Shababa Selim
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All authors contributed to the writing of the article. E.P. and A.W. also researched the data, discussed the content and edited the article prior to submission.

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Correspondence to Ernest Pastor or Aron Walsh.

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Pastor, E., Sachs, M., Selim, S. et al. Electronic defects in metal oxide photocatalysts. Nat Rev Mater 7, 503–521 (2022). https://doi.org/10.1038/s41578-022-00433-0

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