Copper‐Based Nitrides Outperform Phosphides in Nitrate Electroreduction to Ammonia: The Cooperative role of the Cu3N/CuO interface

Binary compounds consisting of Cu(I) and moderately electronegative elements (N, P) are attractive semiconductors for optoelectronic and electrocatalytic applications. This study investigates the electrochemical reduction of nitrate to ammonia (NO3RR) using copper‐based catalysts, specifically Cu3N and Cu3P. Inhibiting the competitive hydrogen evolution reaction and ensuring active hydrogen (H*) for NH3 production during NO3RR pose significant challenges. Our research demonstrates that while Cu3P is effective in the initial reduction of nitrate to nitrite, it fails to produce NH3 at more negative potentials due to competition with the hydrogen evolution reaction (HER). In contrast, Cu3N exhibits remarkable performance, achieving an ammonia yield of a rate of 48.8 mmol h‐1 mmol‐1cat at ‐0.9 VRHE, with high Faradaic efficiency. The formation of a Cu3N/CuO interface during the catalysis is crucial for its activity, facilitating efficient NO3RR through a stepwise reduction mechanism. The study provides insights into the surface modifications and mechanistic aspects of these catalysts during NO3RR, offering guidance for strategically developing more efficient catalysts for nitrate reduction to ammonia.