Neighboring effect in PtCuSnCo alloy catalysts for precisely regulating nitrate adsorption and deoxidation to achieve 100% faradaic efficiency in ammonia synthesis

The electrochemical reduction of nitrate (NO₃⁻) to ammonia (NH₃) (NO₃RR) represents an environmentally sustainable strategy for NH₃ production while concurrently addressing water pollution challenges. Nevertheless, the intrinsic complexity of this multi-step reaction severely constrains both the selectivity and efficiency of NO₃RR. Copper-based electrocatalysts have been extensively investigated for NO₃RR but often suffer from nitrite (NO₂⁻) accumulation, which stems from insufficient NO₃⁻ adsorption strength. This limitation often leads to rapid catalyst deactivation, hindered hydrogenation pathways, and reduced overall efficiency. Herein, we report a one-step green chemical reduction method to synthesize PtCuSnCo quarternary alloy nanoparticles with homogeneously distributed elements. Under practical NO₃⁻ concentrations, the optimized catalyst exhibited an impressive Faradaic efficiency approaching 100% and an outstanding selectivity of 95.6 ± 2.9%. Mechanistic insights uncovered that SnCo sites robustly facilitated NO₃⁻ adsorption, complemented by the proficiency of PtCu sites in NO₃⁻ reduction. The synergistic spatial neighborhood effect between SnCo and PtCu sites efficiently stabilizes NO₃⁻ deoxygenation and suppresses NO₂⁻ accumulation. This tandem architecture achieves a finely tuned balance between adsorption strength and deoxygenation kinetics, enabling highly selective and efficient NO₃RR. Our findings emphasize the indispensable role of engineered multi-metallic catalysts in overcoming persistent challenges of NO₃RR, paving the way for advanced NH₃ synthesis and environmental remediation.