Kirkendall-Effect-Driven Synthesis of Cu/Ru Nanocages for Electrocatalytic Nitrate Reduction via Tandem Catalysis

The high-yield synthesis of uniform Cu/Ru nanostructures is crucial for catalyzing nitrate (NO3-) reduction to ammonia (NH3), yet it remains highly challenging. Herein, we report a facile strategy for synthesizing Cu/Ru bimetallic nanocages in high yield, driven by the Kirkendall effect. This process induces nonequilibrium atomic interdiffusion at the Cu/Ru interface, generating a net outward flux of Cu atoms and a counter-flux of vacancies, which collectively lead to the formation of a uniform nanocage structure. Importantly, the Cu87Ru13 nanocages exhibit superior performance in the electrochemical NO3- reduction reaction (NO3-RR), achieving a maximal Faradaic efficiency (FE) of 91% and an NH3 production rate of 3353 mmol h-1 g-1 at -0.3 V (vs reversible hydrogen electrode (RHE)). In situ characterization reveals that within Cu/Ru nanocages, Cu sites adsorb NO3- and reduce it to *NO2, while Ru sites reduce adsorbed *H, which protonates reaction intermediates to facilitate the conversion of NO3- to NH3.