Highly selective urea electrooxidation coupled with efficient hydrogen evolution

Abstract Electrochemical urea oxidation offers a sustainable avenue for H 2 production and wastewater denitrification within the water-energy nexus; however, its wide application is limited by detrimental cyanate or nitrite production instead of innocuous N 2 . Herein we demonstrate that atomically isolated asymmetric Ni–O–Ti sites on Ti foam anode achieve a N 2 selectivity of 99%, surpassing the connected symmetric Ni–O–Ni counterparts in documented Ni-based electrocatalysts with N 2 selectivity below 55%, and also deliver a H 2 evolution rate of 22.0 mL h –1 when coupled to a Pt counter cathode under 213 mA cm –2 at 1.40 V RHE . These asymmetric sites, featuring oxygenophilic Ti adjacent to Ni, favor interaction with the carbonyl over amino groups in urea, thus preventing premature resonant C⎓N bond breakage before intramolecular N–N coupling towards N 2 evolution. A prototype device powered by a commercial Si photovoltaic cell is further developed for solar-powered on-site urine processing and decentralized H 2 production.