Uniting Synergistic Effect of Single-Ni Site and Electric Field of B- Bridged-N for Boosted Electrocatalytic Nitrate Reduction to Ammonia.

Electrochemical conversion of nitrate, a prevalent water pollutant, to ammonia (NH 3 ) is a delocalized and green path for NH 3 production. Despite the existence of different nitrate reduction pathways, selectively directing the reaction pathway on the road to NH 3 is now hindered by the absence of efficient catalysts. Single-atom catalysts (SACs) are extensively investigated in a wide range of catalytic processes. However, their application in electrocatalytic nitrate reduction reaction (NO 3 - RR) to NH 3 is infrequent, mostly due to their pronounced inclination toward hydrogen evolution reaction (HER). Here, Ni single atoms on the electrochemically active carrier boron, nitrogen doped-graphene (BNG) matrix to modulate the atomic coordination structure through a boron-spanning strategy to enhance the performance of NO 3 - RR is designed. Density functional theory (DFT) study proposes that BNG supports with ionic characteristics, offer a surplus electric field effect as compared to N-doped graphene, which can ease the nitrate adsorption. Consistent with the theoretical studies, the as-obtained NiSA@BNG shows higher catalytic activity with a maximal NH 3 yield rate of 168 µg h -1  cm -2 along with Faradaic efficiency of 95% and promising electrochemical stability. This study reveals novel ways to rationally fabricate SACs' atomic coordination structure with tunable electronic properties to enhance electrocatalytic performance.