Hollow mesoporous carbon supported Co-modified Cu/Cu₂O electrocatalyst for nitrate reduction reaction

The electroreduction of nitrate (NO₃^-) pollutants to ammonia (NH₃) provides a sustainable approach for both wastewater treatment and NH₃ synthesis. However, electroreduction of nitrate requires multi-step electron and proton transfer, resulting in a sluggish reaction rate. Herein, we synthesized a Co-modified Cu/Cu₂O catalyst supported on hollow mesoporous carbon substrates (Co/Cu/Cu₂O-MesoC) by a one-step microwave-assisted reduction method. At -0.25 V vs. reversible hydrogen electrode (RHE), Co/Cu/Cu₂O-MesoC shows a Faradaic efficiency (FE) of 100 ± 1% in 0.1 M NO₃^-. Notably, the maximum NH₃ yield rate (Yield_NH3) reaches 6.416 ± 0.78 mmol mg_cat^-1h^-1 at -0.45 V vs. RHE, which is much better than most of the previous reports. Electrochemical evaluation and in-situ Fourier transform infrared (FTIR) spectroscopy reveal that the addition of Co could promote water electrolysis, and the generated H* is involved in the following hydrogenation of intermediates, ultimately leading to faster kinetics and energetics during electrocatalytic conversion of NO₃^- to NH₃. This synergetic electrocatalysis strategy opens a new avenue for the development of high-activity, selectivity, and stability catalysts.