Understanding the chemical transformations governing the oxygen evolution reaction (OER) in Cu-based electrocatalysts is critical for advancing cost-efficient alkaline water-splitting technologies. In this study, we employ synchrotron-based operando Cu L₃-edge X-ray absorption spectroscopy (XAS) and potentiodynamic techniques to probe the key intermediate species involved in alkaline OER. Our findings reveal that this metastable species exhibits an electronic structure resembling high-valent Cu complexes, particularly those associated with the CuO₂^- ion. Potentiodynamic measurements indicate that the high-valent intermediate emerges at potentials as low as 1.62 V_RHE, coinciding with the oxidative process traditionally attributed to the Cu²⁺ ↔ Cu³⁺ redox transition, suggesting that the formation of the high-valent intermediate is directly linked to this redox process. This work provides valuable insights into the interplay between redox chemistry and catalytic performance in Cu-based OER electrocatalysts and provides further insights into the nature of the chemical species governing the oxygen evolution reaction mechanism.

理解铜基电催化剂中析氧反应（OER）的化学转化对于推进高效低成本碱性水电解技术至关重要。在这项研究中，我们利用同步辐射原位Cu L₃-边X射线吸收光谱（XAS）和恒电位动力学技术来探测碱性OER中的关键中间体物种。我们的发现揭示了这种亚稳态物种具有类似于高价铜配合物的电子结构，特别是与CuO₂^-离子相关的那种。恒电位测量表明，在低至1.62 V_RHE的电势下会出现高价中间体，这与传统上归因于Cu²⁺ ↔ Cu³⁺氧化还原过程的氧化过程相对应，暗示高价中间体的形成直接与这一氧化还原过程相关。这项工作为铜基OER电催化剂中氧化还原化学和催化性能之间的相互作用提供了有价值的见解，并进一步揭示了控制氧气析出反应机制的化学物种的本质。