Product ammonia accumulation limits electrocatalytic nitric oxide reduction

Abstract The electrocatalytic nitric oxide reduction reaction (eNORR) has emerged as a promising route for sustainable ammonia synthesis under ambient conditions. However, its practical efficiency and long-term stability are often constrained by the dynamic reaction microenvironment at the electrode-electrolyte interface. A critical yet frequently overlooked factor in real operating systems is the local accumulation of the ammonia and its adverse interfacial effects. Here, we use in situ Raman spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to directly probe the dynamic evolution of the interfacial structure during eNORR. We demonstrate that accumulated ammonia elevates the local pH, occupies active catalytic sites, impedes reactant adsorption, and rigidifies the interfacial hydrogen-bonding network. These coupled effects collectively lead to a pronounced decline in catalytic activity and operational stability. To address this challenge, we further propose a proton-management strategy based on buffered electrolytes to promote ammonia desorption from the cathode surface, thereby effectively mitigating performance degradation. This work provides fundamental insights into interfacial processes governing nitrogen oxide electroreduction and offers a practical design principle for developing high-performance electrocatalytic systems with enhanced stability and product concentration.