Zhang Jifang, Liu Meng, Wang Haifeng, Guan Shengyang, Ma Guijun
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China.
Techstorm Advanced Material Co. Ltd., Lin-Gang Special Area of China (Shanghai) Pilot Free Trade Zone, Shanghai 201306, P. R. China.
JACS Au. 2025 May 28;5(6):2513-2522. doi: 10.1021/jacsau.5c00131. eCollection 2025 Jun 23.
Operando examination of reaction intermediates during (photo)-electrocatalytic processes, particularly with respect to their kinetics, is a critical but challenging task. Spectroelectrochemical (SEC) methods based on UV-vis spectroscopy offer potential insights into intermediate species, although they are often applied under steady-state conditions. In this work, we employ excitation-modulated absorption spectroscopy (EMAS), which utilizes periodic modulation of either potential or light intensity, to dynamically probe the SEC responses of a hematite (FeO) photoanode, NiFeO -type electrocatalysts, and their composites. Comparison of spectral profiles in the frequency domain under electrocatalytic (EC) and photoelectrocatalytic (PEC) conditions allows for the identification of key reaction intermediates and their corresponding redox rate constants, which further facilitates the revelation of key steps of charge dynamics. Specifically, EC and PEC water oxidation on bare FeO photoanodes proceed via the same reaction intermediate Fe-(IV) with similar kinetics. For composite hematite photoanodes, a faster redox rate of the oxidized catalytic reaction intermediates of the electrocatalyst upon accepting holes from the semiconductor is crucial for achieving a high photocurrent density. These results highlight EMAS as a powerful and versatile tool to understand (photo)-electrocatalytic systems.
在（光）电催化过程中对反应中间体进行原位研究，特别是关于它们的动力学，是一项关键但具有挑战性的任务。基于紫外-可见光谱的光谱电化学（SEC）方法能够为中间体物种提供潜在的见解，尽管它们通常在稳态条件下应用。在这项工作中，我们采用激发调制吸收光谱（EMAS），它利用电位或光强度的周期性调制，来动态探测赤铁矿（Fe₂O₃）光阳极、NiFeOₓ型电催化剂及其复合材料的SEC响应。通过比较电催化（EC）和光电催化（PEC）条件下频域中的光谱轮廓，可以识别关键反应中间体及其相应的氧化还原速率常数，这进一步有助于揭示电荷动力学的关键步骤。具体而言，在裸Fe₂O₃光阳极上的EC和PEC水氧化过程通过相同的反应中间体Fe-(IV)进行，且动力学相似。对于复合赤铁矿光阳极，电催化剂的氧化催化反应中间体在从半导体接受空穴后具有更快的氧化还原速率，这对于实现高光电流密度至关重要。这些结果突出了EMAS作为理解（光）电催化系统的强大且通用的工具。
