Boosting Electrochemical Nitrate Reduction Over a Wide Concentration Range through Constructing Bidirectional Electron Transfer Channels

Electrocatalytic nitrate (NO 3 – ) reduction reaction (NO 3 RR) to ammonia (NH 3 ) provides a sustainable solution for the nitrogen cycle and a new pathway for green NH 3 synthesis. Nevertheless, the NO 3 RR over a wide concentration range remains challenging due to mass transfer resistance at low concentrations and insufficient *H supply at high concentrations. Herein, we designed the three-layer composite catalyst (Co/Cu/NC) by embedding Co@Cu core–shell nanoparticles into N-doped carbon substrates (Co@Cu x /NC, x = Cu/Co atomic ratio) for NO 3 RR. The optimal catalyst Co@Cu 1.0 /NC exhibits a remarkable FE NH3 over a wide potential window with the increase in the NO 3 – concentration from 1 to 2000 mM. Both experimental and theoretical studies have demonstrated that the electron-deficient Cu sites formed by the bidirectional electron transport to Co and NC are favorable for NO 3 – adsorption and conversion to *NO 2 . Simultaneously, the electron-rich Co sites efficiently facilitate H 2 O dissociation, supplying sufficient *H to the adjacent Cu sites to reduce the *NO 2 intermediate to NH 3 . As a result, the catalyst Co@Cu 1.0 /NC exhibits excellent NO 3 RR performance over a record-wide NO 3 – concentration range covering the textile industry effluents to nuclear waste. The bidirectional electron transport channel provides a novel guideline for the design of NO 3 RR electrocatalysts over the full concentration range.