pH‐Dependent Electroreduction of Nitrate on Fe Single‐Atom Catalyst

Electrochemical nitrate reduction reaction (NO 3 RR) has received considerable attention due to its potential for the denitrification of wastewater and sustainable NH 3 production. Among various catalysts for NO 3 RR, Fe−N−C single‐atom catalyst has attracted significant interest due to its well‐defined active sites and high stability across various media. Here, we investigate the pH dependence of NO 3 RR on Fe−N−C by combining experiments and density functional theory (DFT) calculations. The Fe−N−C catalyst achieves high activity and >80% Faradaic efficiency for NH 3 production in the NO 3 RR across acidic, neutral, and alkaline electrolytes, while the hydrogen evolution reaction (HER) exhibits the strongest competition with NO 3 RR in alkaline electrolyte. DFT calculations identify the NHO*‐mediated pathway as the most favorable for NO 3 RR on Fe−N−C and further reveal the pH dependence of the potential‐determining steps for both NO 3 RR and HER, elucidating the origin of the pH‐dependent selectivity. Our studies provide new mechanistic insights into the NO 3 RR on single‐atom catalysts and guide the design of broad pH‐range electrocatalysts for efficient and versatile nitrate recycling.