Electrochemical conversion of NO3- to NH3 production is of great environmental significance for water pollution treatment and can artificially close the nitrogen cycle. However, direct nine proton and eight electron transfer leads to low Faraday efficiency (FE) and yield. Herein, the single copper site immobilized on N, P co-doped carbon substrates (Cu-N4/P) was prepared for efficient NO3–to-NH3 conversion. Benefiting from electronic redistribution of Cu site induced by the introduction of the less electronegative element P, Cu-N4/P catalyst has superior catalytic properties to the comparison sample, including 100% NO3- conversion, high FE (96.12%) and NH3 yield (124.22 mmol/(h·gcat)). Density functional theory (DFT) explains the effective operation mechanism that P doping can promote the spontaneous hydrogenation of *NO to form *NOH, thus promoting the formation of NH3 from NO3- reduction reaction. The heteroatom doping strategy mentioned proposes a new approach for promoting NO3–to-NH3 conversion at atomic level catalytic sites.
