Oxygen Vacancy-Controlled CuO x /N,Se Co-Doped Porous Carbon via Plasma-Treatment for Enhanced Electro-Reduction of Nitrate to Green Ammonia.

The electrochemical nitrate reduction reaction (NO 3 RR) is of significance in regards of environmentally friendly issues and green ammonia production. However, relatively low performance with a competitive hydrogen evolution reaction (HER) is a challenge to overcome for the NO 3 RR. In this study, oxygen vacancy-controlled copper oxide (CuO x ) catalysts through a plasma treatment are successfully prepared and supported on high surface area porous carbon that are co-doped with N, Se species for its enhanced electrochemical properties. The oxygen vacancy-increased CuO x catalyst supported on the N,Se co-doped porous carbon (CuO x -H/NSePC) exhibited the highest NO 3 RR performance with faradaic efficiency (FE) of 87.2% and yield of 7.9 mg cm -2  h -1 for the ammonia production, representing significant enhancements of FE and ammonia yield as compared to the un-doped or the oxygen vacancy-decreased catalysts. This high performance should be attributed to a significant increase in the catalytic active sites with facilitated energetics from strategies of doping the catalytic materials and weakening the N─O bonding strength for the adsorption of NO 3 - ions on the modulated oxygen vacancies. This results show a promise that co-doping of heteroatoms and regulating of oxygen vacancies can be key factors for performance enhancement, suggesting new guidelines for effective catalyst design of NO 3 RR.