Single-Particle Measurements Reveal the Origin of Low Solar-to-Hydrogen Efficiency of Rh-Doped SrTiO3 Photocatalysts

Brian Zutter; Zejie Chen; Luisa Barrera; William Gaieck; Aliya S Lapp; Kenta Watanabe; Akihiko Kudo; Daniel V Esposito; Rohini Bala Chandran; Shane Ardo; A Alec Talin

doi:10.1021/acsnano.3c01448

Single-Particle Measurements Reveal the Origin of Low Solar-to-Hydrogen Efficiency of Rh-Doped SrTiO₃ Photocatalysts

ACS Nano. 2023 May 23;17(10):9405-9414. doi: 10.1021/acsnano.3c01448. Epub 2023 May 10.

Authors

Brian Zutter¹, Zejie Chen², Luisa Barrera³, William Gaieck², Aliya S Lapp¹, Kenta Watanabe⁴, Akihiko Kudo⁴, Daniel V Esposito⁵, Rohini Bala Chandran³, Shane Ardo^{2

6

7}, A Alec Talin¹

Affiliations

¹ Materials Physics Department, Sandia National Laboratories, Livermore, California 94550, United States.
² Department of Chemistry, University of California, Irvine, California 92697, United States.
³ Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States.
⁴ Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
⁵ Department of Chemical Engineering, Columbia University, New York, New York 10027, United States.
⁶ Department of Materials Science and Engineering, University of California, Irvine, California 92697, United States.
⁷ Department of Chemistry and Biomolecular Engineering, University of California, Irvine, California 92697, United States.

PMID: 37163708
DOI: 10.1021/acsnano.3c01448

Abstract

Solar-powered photochemical water splitting using suspensions of photocatalyst nanoparticles is an attractive route for economical production of green hydrogen. SrTiO₃-based photocatalysts have been intensely investigated due to their stability and recently demonstrated near-100% external quantum yield (EQY) for water splitting using wavelengths below 360 nm. To extend the optical absorption into the visible, SrTiO₃ nanoparticles have been doped with various transition metals. Here we demonstrate that doping SrTiO₃ nanoparticles with 1% Rh introduces midgap acceptor states which reduce the free electron concentration by 5 orders of magnitude, dramatically reducing built-in potentials which could otherwise separate electron-hole (e-h) pairs. Rhodium states also function as recombination centers, reducing the photocarrier lifetime by nearly 2 orders of magnitude and the maximum achievable EQY to 10%. Furthermore, the absence of built-in electric fields within Rh-doped SrTiO₃ nanoparticles suggests that modest e-h separation can be achieved by exploiting a difference in mobility between electrons and holes.

Keywords: photoelectrochemical water splitting; semiconductor heterojunction; semiconductor nanoparticle; strontium titanate; transition metal doping.