Understanding Electrolyte Effects on Cation-Enhanced Electrocatalytic Ammonia Oxidation Over the Pt Surface in...

A fundamental understanding of the dynamic behavior at the electrode/electrolyte interface is pivotal for electrocatalyst design and optimization. However, the effect of electrolyte cations at a complicated electrical double layer (EDL) on the electrochemical kinetics of ammonia oxidation (AOR) remains unexplored. Herein, we first construct the explicit solid-liquid interface model to investigate the physical origin of alkaline metal cations (AM⁺) such as K⁺ on the reactive kinetics of AOR through the constrained molecule dynamics with a slow-growth sampling (SG-AIMD) method and operando Fourier transform infrared spectroscopy (FTIR) measurement, taking the Pt electrode as a model catalyst. Surface Pourbaix diagram results demonstrate that the introduction of K⁺ can significantly alter the electrochemical surface state of the Pt(100) surface with more adsorbed OH_ad species. The enhanced OH_ad coverage dramatically regulates the interfacial hydrogen-bond network, which plays a critical role in the kinetics of the interfacial proton-coupled electron transfer (PCET) process. As a result, the first dehydrogenation barrier of *NH₃ to *NH₂ through the PCET step was ulteriorly decreased from 0.95 to 0.78 eV under K⁺ conditions using SG-AIMD simulations. This work highlights the indispensable role of interfacial water structure enhanced by the cation effect in AOR efficiency.