Liu Siqin, Wu Lei, Tang Daojian, Xue Jing, Dang Kun, He Hanbin, Bai Shuming, Ji Hongwei, Chen Chuncheng, Zhang Yuchao, Zhao Jincai
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.
University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
J Am Chem Soc. 2023 Nov 1;145(43):23849-23858. doi: 10.1021/jacs.3c09410. Epub 2023 Oct 20.
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-FeO, BiVO, TiO, plasmonic Au/TiO, and nickel-iron oxyhydroxide (NiFeOOH)-modified silicon (Si)] by combining the rate law analysis of HO 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 HO, 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 NiFeOOH 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 NiFeOOH 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.
加速质子转移已被证明是提高半导体光阳极上的水氧化反应的关键。在此，我们通过结合HO分子的速率定律分析、H/D动力学同位素效应（KIE）以及原位光谱研究，研究了五种典型光阳极[即α-FeO、BiVO、TiO、等离子体Au/TiO以及氢氧化氧镍（NiFeOOH）修饰的硅（Si）]上的水氧化反应的质子耦合电子转移（PCET）。对于HO的速率定律分析，观察到了意想不到的通用半级动力学，这表明是一个连续的质子-电子转移途径，这是导致水氧化性能迟缓的限速因素。观察到NiFeOOH电催化剂的表面改性打破了这一限制，并表现出正常的一级动力学，同时H/D KIE值大大提高，使水氧化的周转频率提高了1个数量级。首次发现NiFeOOH是一种PCET调节剂。速率定律分析说明了一种调节半导体表面水氧化反应的PCET动力学的有效策略。
