Linking in situ charge accumulation to electronic structure in doped SrTiO3 reveals design principles for hydrogen-evolving photocatalysts

Benjamin Moss; Qian Wang; Keith T Butler; Ricardo Grau-Crespo; Shababa Selim; Anna Regoutz; Takashi Hisatomi; Robert Godin; David J Payne; Andreas Kafizas; Kazunari Domen; Ludmilla Steier; James R Durrant

doi:10.1038/s41563-020-00868-2

Linking in situ charge accumulation to electronic structure in doped SrTiO₃ reveals design principles for hydrogen-evolving photocatalysts

Nat Mater. 2021 Apr;20(4):511-517. doi: 10.1038/s41563-020-00868-2. Epub 2021 Jan 11.

Authors

Benjamin Moss^{1

2}, Qian Wang^{3

4}, Keith T Butler⁵, Ricardo Grau-Crespo⁶, Shababa Selim^{1

2}, Anna Regoutz⁷, Takashi Hisatomi⁸, Robert Godin^{1

9}, David J Payne¹⁰, Andreas Kafizas^{1

11}, Kazunari Domen^{6

12}, Ludmilla Steier¹³, James R Durrant^{1

2}

Affiliations

¹ Department of Chemistry, Imperial College London, London, UK.
² Centre for Processable Electronics, Imperial College London, London, UK.
³ Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
⁴ Department of Chemistry, University of Cambridge, Cambridge, UK.
⁵ SciML, Scientific Computing Division, Rutherford Appleton Laboratory, Harwell, UK.
⁶ Department of Chemistry, University of Reading, Reading, UK.
⁷ Department of Chemistry, University College London, London, UK.
⁸ Research Initiative for Supra-Materials, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Nagano, Japan.
⁹ Department of Chemistry, University of British Columbia, Kelowna, British Columbia, Canada.
¹⁰ Department of Materials, Imperial College London, London, UK.
¹¹ Grantham Institute, Imperial College London, London, UK.
¹² Office of University Professor, The University of Tokyo, Tokyo, Japan.
¹³ Department of Chemistry, Imperial College London, London, UK. l.steier@imperial.ac.uk.

PMID: 33432143
DOI: 10.1038/s41563-020-00868-2

Abstract

Recently, high solar-to-hydrogen efficiencies were demonstrated using La and Rh co-doped SrTiO₃ (La,Rh:SrTiO₃) incorporated into a low-cost and scalable Z-scheme device, known as a photocatalyst sheet. However, the unique properties that enable La,Rh:SrTiO₃ to support this impressive performance are not fully understood. Combining in situ spectroelectrochemical measurements with density functional theory and photoelectron spectroscopy produces a depletion model of Rh:SrTiO₃ and La,Rh:SrTiO₃ photocatalyst sheets. This reveals remarkable properties, such as deep flatband potentials (+2 V versus the reversible hydrogen electrode) and a Rh oxidation state dependent reorganization of the electronic structure, involving the loss of a vacant Rh 4d mid-gap state. This reorganization enables Rh:SrTiO₃ to be reduced by co-doping without compromising the p-type character. In situ time-resolved spectroscopies show that the electronic structure reorganization induced by Rh reduction controls the electron lifetime in photocatalyst sheets. In Rh:SrTiO₃, enhanced lifetimes can only be obtained at negative applied potentials, where the complete Z-scheme operates inefficiently. La co-doping fixes Rh in the 3+ state, which results in long-lived photogenerated electrons even at very positive potentials (+1 V versus the reversible hydrogen electrode), in which both components of the complete device operate effectively. This understanding of the role of co-dopants provides a new insight into the design principles for water-splitting devices based on bandgap-engineered metal oxides.

Abstract

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