Mechanistic Insights into the Intercorrelation between the Hydrogen Evolution Reaction and Nitrate Reduction to Ammonia: A Review

The industrial synthesis of ammonia is characterized by harsh conditions, high energy consumption, and significant environmental pollution. In contrast, electrocatalytic nitrate reduction under ambient conditions presents a potential green and sustainable alternative to the energy-intensive industrial process. Hydrogen evolution reaction (HER), one of the most fundamental reactions in nature, is closely linked to the reaction mechanism of electrocatalytic nitrate reduction to ammonia (NRA), particularly in electrocatalysis, as both processes rely on proton transfer and electron exchange. The reactive hydrogen intermediates in HER often interact with the hydrogenation process in NRA, making it crucial to understand their interplay for the development of efficient electrocatalysts. By tuning the properties of electrocatalysts, water splitting can be elevated or suppressed to a point that enhances the selectivity of NRA, thereby optimizing ammonia production yields. However, there has been little systematic review of the mechanistic relationship between HER and NRA. This perspective provides a comprehensive overview of theoretical and experimental advances in HER and NRA processes, with a particular emphasis on their mechanistic relevance.