Observation of Transition from Rate Law to Butler–Volmer Controlled Water Oxidation Kinetics on Hematite Photoanodes
Despite its central role in photoelectrochemical (PEC) water splitting, the mechanistic pathway of water oxidation on metal oxides remains unresolved, with population-based and Butler-Volmer (BV) models offering distinct views on how surface valence band holes drive the reaction. Here, we bring together these two perspectives by combining operando photoinduced absorption (PIA) spectroscopy with photocurrent analyses on α-Fe<sub>2</sub>O<sub>3</sub> (hematite) photoanodes as a function of light intensity. We find a crossover from population-controlled, rate law water oxidation at low hole densities to a BV-like, potential driven regime at high densities, triggered by band edge unpinning once surface M-OH species are fully oxidized, and excess holes accumulate without compensation. This mechanistic transition unifies competing models of interfacial charge transfer and reveals design principles for optimizing water oxidation in metal oxide photoelectrodes.
Authors
- Benjamin Moss (ORCID: https://orcid.org/0000-0002-5786-1587)
- Daniele Benetti (ORCID: https://orcid.org/0000-0001-6665-3686)
- Cindy Tseng
- Simone Piccinin (ORCID: https://orcid.org/0000-0002-3601-7141)
- Detre Teschner (ORCID: https://orcid.org/0000-0001-5021-6748)
- T. Alwyn Jones (ORCID: https://orcid.org/0000-0002-0067-3382)
- James Robert Durrant (ORCID: https://orcid.org/0000-0001-8353-7345)
- Tianhao He (ORCID: https://orcid.org/0009-0003-1164-7782)
- Michael Grätzel
- Andreas Kafizas
Institutions
- California Institute of Technology (US)
- Los Alamos National Laboratory (US)
- Fritz Haber Institute of the Max Planck Society (DE)
- Centre for Process Innovation (GB)
- University of Oxford (GB)
- Sustainability Institute (ZA)
- Istituto Officina dei Materiali (IT)
- Max Planck Institute for Chemical Energy Conversion (DE)
- Institut de Chimie (FR)
- Consorzio Roma Ricerche (IT)
- Institute for Sustainability (GB)
- Imperial College London (GB)
- École Polytechnique Fédérale de Lausanne (CH)
Publication Details
- Journal
- Journal of the American Chemical Society
- Published
- 2026-01-29
- DOI
- https://doi.org/10.1021/jacs.5c18734
- Primary Topic
- Iron oxide chemistry and applications
- Type
- article
- Field-Weighted Citation Impact
- 0.00