Wei Ruifang, Li Dongfeng, Zhou Panwang, Liu Runze, Ni Chenwei, Cheng Zeyu, Wang Xiuli, Li Can
School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China.
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, Dalian 116023, China.
J Am Chem Soc. 2025 Jul 9;147(27):23473-23481. doi: 10.1021/jacs.4c18273. Epub 2025 Jun 29.
In the electrocatalytic oxygen evolution reaction (OER), it has been a long-standing issue to establish the relationship between intermediate kinetics, catalyst structures, and OER activity, which is challenging due to the difficulty in following the intermediate kinetics and charge dynamics simultaneously. Here, using home-built electrochemical transient absorption (EC-TA) spectroscopy, we succeeded in resolving the kinetics of the first intermediate (*OH species) in the OER catalytic cycle on MnO-based electrocatalysts, which is consistent with microkinetics simulation. In the formation process of *OH species, proton transfer is slower than electron transfer, resulting in the continuous formation of *OH species after the interruption of the potential pulse. Based on a comparison of *OH formation rates in four MnO-based catalysts with different electron configurations, the formation rates of *OH species are highly dependent on the coordination symmetry of the corner-shared MnO octahedron in the catalyst. The formation rate of *OH species in a catalyst with a corner-shared MnO octahedron of D symmetry exhibits a ∼100-fold (2.33 × 10 s) increase compared with that in a catalyst with a corner-shared MnO octahedron of D symmetry (2.45 × 10 s). More importantly, the formation rates of *OH species show a positive correlation with the reaction rates of the rate-determining step (RDS) in the OER catalytic cycle. The insight into the formation kinetics of the first OER intermediate in the OER processes indicates the crucial role of the initial rate in the OER catalytic cycle and sheds light on the OER kinetic mechanism on electrocatalysts.
在电催化析氧反应（OER）中，建立中间体动力学、催化剂结构与OER活性之间的关系一直是个长期存在的问题，由于难以同时跟踪中间体动力学和电荷动力学，这一问题颇具挑战性。在此，我们利用自制的电化学瞬态吸收（EC-TA）光谱，成功解析了MnO基电催化剂上OER催化循环中首个中间体（OH物种）的动力学，这与微观动力学模拟结果一致。在OH物种的形成过程中，质子转移比电子转移慢，导致在电势脉冲中断后OH物种持续形成。基于对四种具有不同电子构型的MnO基催化剂中OH形成速率的比较，OH物种的形成速率高度依赖于催化剂中角共享MnO八面体的配位对称性。具有D对称性角共享MnO八面体的催化剂中OH物种的形成速率比具有D对称性角共享MnO八面体的催化剂（2.45×10 s）高出约100倍（2.33×10 s）。更重要的是，*OH物种的形成速率与OER催化循环中速率决定步骤（RDS）的反应速率呈正相关。对OER过程中首个OER中间体形成动力学的深入了解揭示了初始速率在OER催化循环中的关键作用，并为电催化剂上的OER动力学机制提供了线索。
