Transition from Sequential to Concerted Proton-Coupled Electron Transfer of Water Oxidation on Semiconductor Photoanodes

Siqin Liu; Lei Wu; Daojian Tang; Jing Xue; Kun Dang; Hanbin He; Shuming Bai; Hongwei Ji; Chuncheng Chen; Yuchao Zhang; Jincai Zhao

doi:10.1021/jacs.3c09410

Transition from Sequential to Concerted Proton-Coupled Electron Transfer of Water Oxidation on Semiconductor Photoanodes

J Am Chem Soc. 2023 Nov 1;145(43):23849-23858. doi: 10.1021/jacs.3c09410. Epub 2023 Oct 20.

Authors

Siqin Liu^{1

2}, Lei Wu^{1

2}, Daojian Tang^{1

2}, Jing Xue^{1

2}, Kun Dang^{1

2}, Hanbin He^{1

2}, Shuming Bai^{1

2}, Hongwei Ji^{1

2}, Chuncheng Chen^{1

2}, Yuchao Zhang^{1

2}, Jincai Zhao^{1

2}

Affiliations

¹ Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
² University of Chinese Academy of Sciences, Beijing 100049, P. R. China.

PMID: 37861695
DOI: 10.1021/jacs.3c09410

Abstract

Accelerating proton transfer has been demonstrated as key to boosting water oxidation on semiconductor photoanodes. Herein, we study proton-coupled electron transfer (PCET) of water oxidation on five typical photoanodes [i.e., α-Fe₂O₃, BiVO₄, TiO₂, plasmonic Au/TiO₂, and nickel-iron oxyhydroxide (Ni_1-xFe_xOOH)-modified silicon (Si)] by combining the rate law analysis of H₂O molecules with the H/D kinetic isotope effect (KIE) and operando spectroscopic studies. An unexpected and universal half-order kinetics is observed for the rate law analysis of H₂O, referring to a sequential proton-electron transfer pathway, which is the rate-limiting factor that causes the sluggish water oxidation performance. Surface modification of the Ni_1-xFe_xOOH electrocatalyst is observed to break this limitation and exhibits a normal first-order kinetics accompanied by much enhanced H/D KIE values, facilitating the turnover frequency of water oxidation by 1 order of magnitude. It is the first time that Ni_1-xFe_xOOH is found to be a PCET modulator. The rate law analysis illustrates an effective strategy for modulating PCET kinetics of water oxidation on semiconductor surfaces.