High Mass Activity of a Dendritic Ag–Cu Relay Catalyst for Nitrate to Ammonia Electroreduction

Owing to the growing demand for NH3 as an energy carrier, developing alternative NH3 production routes that overcome the limitations of the Haber-Bosch process is essential. The electrochemical nitrate reduction reaction (NO3RR) offers a sustainable alternative to thermochemical ammonia synthesis by simultaneously mitigating nitrate pollution and enabling renewable-energy-driven NH3 production. Here, we demonstrate high mass activity for NH3 production through the electrochemical NO3RR using a dendritic Ag-Cu relay catalyst, highlighting the NO3RR as a sustainable alternative to the Haber-Bosch process. The dendritic morphology of the Ag-Cu catalyst, fabricated by a simple, compact, and scalable galvanic-displacement method, maximizes the electroactive surface area of Ag per unit loading and induces relay effect between Cu and Ag. A mass activity of 7.34 mol h-1·g-1, with a Faradaic efficiency of 96.4%, representing a 1.2-fold improvement over the state-of-the-art performance under alkaline media, was achieved. The catalyst exhibits excellent performance in a practical full-cell configuration, highlighting its potential as a promising alternative or complementary pathway to the conventional Haber-Bosch ammonia synthesis.