Observation of Transition from Rate Law to Butler–Volmer Controlled Water Oxidation Kinetics on Hematite Photoanodes
Year: 2026
Type: article
Abstract: 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-Fe2O3 (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 optimising water oxidation in metal oxide photoelectrodes.
DOI: 10.1021/jacs.5c18734
Institutions: Imperial College London, California Institute of Technology, Resnick Sustainability Institute, Fritz Haber Institute of the Max Planck Society, Max Planck Institute for Chemical Energy Conversion, Los Alamos National Laboratory, École Polytechnique Fédérale de Lausanne, Istituto Officina dei Materiali, National Research Council, University of Oxford
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W7126066020