Boosting Efficient Electrochemical Nitrate Reduction to Ammonia through Active Co–P Catalytic Centers

The electrochemical reduction of nitrate to ammonia is a promising approach for nitrogen resource recovery and environmental remediation. In this study, we investigate the catalytic performance of cobalt phosphide incorporated in the carbon skeleton (CoP/C) as an efficient catalyst for this reaction. The strong interaction between Co and P constructs a unique electronic structure for the catalyst, enabling its catalytic performance and stability to be significantly superior to that of metal Co, cobalt phosphate (Co(PO₃)₂), or cobalt oxide (Co₃O₄). In situ Raman spectroscopy and online differential electrochemical mass spectrometry were employed to identify the intermediate products formed during the catalytic process, providing valuable insights into the reaction mechanism. Furthermore, first-principles calculations highlighted the significant role of Co-P active species in promoting the selectivity of the catalytic process. Consequently, the CoP/C catalyst achieves a peak Faradaic efficiency of 97.5% at -0.2 V versus the reversible hydrogen electrode (RHE) and a peak ammonia yield of 4.2 mol g_cat^-1 h^-1 at -0.6 V versus RHE. Our findings suggest that optimizing the Co-P interaction within the CoP/C catalyst could lead to improved efficiency in the electrochemical reduction of nitrate, paving the way for sustainable ammonia synthesis.