Rate law analysis of water oxidation on a hematite surface.
Water oxidation is a key chemical reaction, central to both biological photosynthesis and artificial solar fuel synthesis strategies. Despite recent progress on the structure of the natural catalytic site, and on inorganic catalyst function, determining the mechanistic details of this multiredox reaction remains a significant challenge. We report herein a rate law analysis of the order of water oxidation as a function of surface hole density on a hematite photoanode employing photoinduced absorption spectroscopy. Our study reveals a transition from a slow, first order reaction at low accumulated hole density to a faster, third order mechanism once the surface hole density is sufficient to enable the oxidation of nearest neighbor metal atoms. This study thus provides direct evidence for the multihole catalysis of water oxidation by hematite, and demonstrates the hole accumulation level required to achieve this, leading to key insights both for reaction mechanism and strategies to enhance function.
†Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.
Florian
F
Le Formal
†Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.
Ernest
E
Pastor
‡Institut des Sciences et Ingénierie Chimiques, Laboratory of Photonics and Interfaces, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
S David
SD
Tilley
†Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.
Camilo A
CA
Mesa
†Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.
Stephanie R
SR
Pendlebury
‡Institut des Sciences et Ingénierie Chimiques, Laboratory of Photonics and Interfaces, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
Michael
M
Grätzel
†Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.
James R
JR
Durrant