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-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 mgNH3-N cm-2 h-1 (ca. 1.18 mmol mgcat. - 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 mgNH3-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-NC are revealed by the comprehensive electrochemical evaluations and in-depth analysis of critical parameters.