Le Formal Florian, Pastor Ernest, Tilley S David, Mesa Camilo A, Pendlebury Stephanie R, Grätzel Michael, Durrant James R
†Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.
‡Institut des Sciences et Ingénierie Chimiques, Laboratory of Photonics and Interfaces, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
J Am Chem Soc. 2015 May 27;137(20):6629-37. doi: 10.1021/jacs.5b02576. Epub 2015 May 15.
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.
水氧化是一种关键的化学反应，对于生物光合作用和人工太阳能燃料合成策略都至关重要。尽管最近在天然催化位点的结构以及无机催化剂功能方面取得了进展，但确定这种多氧化还原反应的机理细节仍然是一项重大挑战。我们在此报告了一项速率定律分析，该分析研究了利用光致吸收光谱法，水氧化反应的级数与赤铁矿光阳极上表面空穴密度之间的函数关系。我们的研究揭示了一种转变，即在低累积空穴密度下，反应为缓慢的一级反应；而一旦表面空穴密度足以使相邻的金属原子发生氧化，反应则转变为更快的三级反应机制。因此，本研究为赤铁矿催化水氧化的多空穴催化提供了直接证据，并证明了实现这一过程所需的空穴积累水平，从而为反应机理和增强功能的策略提供了关键见解。
