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.