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.