Ammonia‐Resistant Carbon‐Encapsulated Cobalt Catalyst for Electrocatalytic Nitrate Reduction to Volatile Ammonia

Abstract

ABSTRACT Electrocatalytic nitrate reduction to ammonia presents a promising route for sustainable nitrogen utilization; however, current efforts remain largely confined to optimizing synthesis efficiency, with insufficient attention paid to the concurrent challenge of ammonia separation—a key bottleneck for scalable deployment. Here, we report carbon‐shell‐encapsulated cobalt nanoparticles (Co@C), which uniquely enable integrated ammonia synthesis and in situ gas‐phase purification under strongly alkaline conditions. In both sequencing batch and continuous‐flow electrolyzers, Co@C delivers a robust nitrate‐to‐ammonia Faradaic efficiency of 92.4%, maintaining performance even in the presence of exogenous ammonia. Critically, the high‐pH environment shifts the NH 3 /NH 4 + equilibrium toward volatile NH 3 , enabling spontaneous volatilization and direct gaseous collection. Combined experimental and theoretical analyses demonstrate that the carbon shells confer dual functionality: they physically suppress Co leaching while electronically modulating surface adsorption to weaken NH 3 binding and accelerate desorption. Our work establishes a catalyst design principle centered on ammonia resistance and introduces an electrochemical platform that unifies synthesis, separation, and purification in a single step.