Ni单原子催化剂表面CO2电还原动力学的电化学谱学解析

针对Ni单原子催化剂表面的CO₂电还原反应(CO₂RR), 提出了以Ni为活性位点的“单中心”机理以及同时借助Ni位点还原和碳氮锚定位水解的“双功能”机理. 依据稳态极化的实验结果, 开展了CO₂RR的动力学解析与模型参数的敏感性分析; 借助暂态模型方程, 分别获取可表达CO₂RR线性与非线性频响特征的电化学阻抗谱(EIS)与总谐波失真(THD)谱. 研究结果表明, CO₂的溶解分压对CO₂RR活性影响最显著. 若CO₂RR遵循“单中心”机理, Ni位点COOH_ads的形成为速率控制步骤; 但若为“双功能”机理, 碳氮锚定位的水解与Ni位点的CO_2,ads还原同为速率控制步骤. EIS理论上可用于区分CO₂RR的“单中心”机理与“双功能”机理; 与之相比, THD谱在CO₂RR的机理识别中并无优势.

Electrochemical Spectroscopy Analysis for Kinetics of the CO2 Electroreduction Reaction on Ni Single Atom Catalysts †

Single site mechanism and bi-function mechanism were both put forward for CO₂ electro-reduction reaction(CO₂RR) on the carbon-nitride anchoring Ni single atoms catalysts. The former is specific to the CO₂RR only on the active site Ni and the latter considers both reductions on the Ni site and water spitting on the anchoring carbon nitride site. Kinetic analysis of the CO₂RR as well as sensitivity analysis for the model parameters were both performed by means of static CO₂RR models and experimental polarizations. Electrochemical impedance spectroscopy(EIS) and total harmonic distortion(THD) spectroscopy were also simulated using dynamic CO₂RR models to explore its linear and nonlinear frequency response behaviors, respectively. It is suggested that CO₂ concentration is the most sensitive parameters to CO₂RR performance. The elemental step to form COOH_ads is the rate determines step as the CO₂RR follows the single site mechanism. As for the bi-function mechanism, both CO_2,ads electro-reduction on the Ni site and water splitting on the carbon nitride site are rate-determining steps of the CO₂RR. Transient simulation of CO₂RR reveals that the EIS is able to tell the difference of the single site mechanism from the bi-function mechanism theoretically over the THD spectroscopy.