Dual enhancement of Cu₂S/CuO nanocomposites in N-Doped porous carbon for highly efficient electrochemical nitrate reduction to ammonia

Electrocatalytic NO₃⁻ reduction reaction (NO₃RR) to NH₃ emerges as a compelling solution for addressing nitrate pollution while simultaneously producing valuable ammonia under ambient conditions. In this work, we present a strategic concept of dual enhancement for NO₃RR electrocatalyst, which involves N-doped porous carbon that accelerates the mass transport of nitrate and concurrent Cu species (Cu₂S/CuO) that fosters a preference for NH₃ generation. With this strategy, the Cu₂S/CuO[sbnd]NC catalyst exhibits augmented removal capacity for nitrate and improved ammonia production. It achieves an ammonia faradaic efficiency of 88.6 % and a yield rate of 6.63 mg_NH3[sbnd]N cm⁻² h⁻¹ (ca. 1.18 mmol mg_cat.⁻¹ h⁻¹) at −0.6 V versus the reversible hydrogen electrode. At −1.0 V, it delivers an impressive yield rate of 12.65 mg_NH3-_N h⁻¹ cm⁻², which is at the top level for Cu-based catalysts. The effect of critical parameter and reduction pathway of NO₃RR over Cu₂S/CuO[sbnd]NC are revealed by the comprehensive electrochemical evaluations and in-depth analysis of critical parameters.