Electrical Pulse-Driven Periodic Self-Repair of Cu-Ni Tandem Catalyst for Efficient Ammonia Synthesis from Nitrate.

Abstract

Electrocatalytic nitrate reduction sustainably produces ammonia and alleviates water pollution, yet challenging due to the kinetic mismatch and hydrogen evolution competition. Cu/Cu2O heterojunction is proven effective to break the rate-determining NO3--to-NO2- step for efficient NH3 conversion, while it is unstable by electrochemical reconstruction. Here we report a programmable pulsed electrolysis strategy to achieve reliable Cu/Cu2O structure, where Cu is oxidized to CuO during oxidation pulse, then regenerating Cu/Cu2O upon reduction. Alloying with Ni further modulates hydrogen adsorption, which transfers from Ni/Ni(OH)2 to N-containing intermediates on Cu/Cu2O, promoting NH3 formation with a high NO3--to-NH3 Faraday efficiency (88.0 ± 1.6%, pH 12) and NH3 yield rate (583.6 ± 2.4 μmol cm-2 h-1) under optimal pulsed conditions. This work provides new insights to in situ electrochemically regulate catalysts for NO3--to-NH3 conversion.