Electrocatalytic current density and especially onset potential or overpotential, as the key parameters for evaluating electrocatalytic performance, are problematic metrics when electron-consuming side processes can take place. This includes the widely studied electrocatalytic oxygen evolution reaction (OER), which is often accompanied by anodic currents associated with the activation or degradation of the catalyst and/or support. Herein, we use an online chip-based electrochemistry–mass spectrometry (chip EC-MS) system to decouple the OER from the complex electrochemical reactions for a graphene-supported ruthenium (Ru) catalyst with high OER activity in an acidic medium. In this manner, we can quantitatively evaluate the current contribution from the OER during cyclic voltammetry (CV) tests and chronopotentiometry (CP) tests and are thus enabled to realize the accurate measurement of the onset potential and Faradaic efficiency (FE) toward the OER. The OER process, including the activation, steady-state, and degradation processes, as well as the side reaction, is also studied using such a chip EC-MS technique. This work is of practical importance to clarify some critical issues remaining in the study of OER electrocatalysis.

中文翻译：

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在线电化学-质谱法评估负载型催化剂的酸性析氧反应

电催化电流密度，尤其是起始电位或过电位，作为评估电催化性能的关键参数，在发生消耗电子的副过程时是有问题的指标。这包括广泛研究的电催化析氧反应 (OER)，该反应通常伴随着与催化剂和/或载体的活化或降解相关的阳极电流。在此，我们使用基于在线芯片的电化学-质谱（芯片 EC-MS）系统将 OER 与复杂电化学反应中的 OER 分离，以在酸性介质中具有高 OER 活性的石墨烯负载钌（Ru）催化剂。以这种方式，我们可以在循环伏安法 (CV) 测试和计时电位法 (CP) 测试期间定量评估 OER 的电流贡献，从而能够实现对 OER 的起始电位和法拉第效率 (FE) 的准确测量。还使用这种芯片 EC-MS 技术研究了 OER 过程，包括活化、稳态和降解过程以及副反应。这项工作对于阐明 OER 电催化研究中存在的一些关键问题具有实际意义。