Regulating the Competitive Adsorption of Urea and OH ⁻ via Brønsted Base Intercalated Nickel Sites for Highly Selective Urea Oxidation

Abstract The competitive adsorption of urea and OH − induces undesired oxygen evolution reaction (OER), severely hindering the development of urea electrolysis. Herein, Brønsted base SnO 3 2− intercalated NiOOH (NiOOH─SnO 3 2− ) is constructed through in situ surface reconstruction of intermetallic Ni 3 Sn 2 . The incorporation of SnO 3 2− renders the catalyst surface negatively charged to inhibit OH − adsorption via electrostatic repulsion. Concurrently, theoretical calculations reveal that SnO 3 2− intercalation into NiOOH upshifts the d ‐band center of Ni by stretching Ni─O bonds, thus strengthening urea adsorption. Furthermore, SnO 3 2− in NiOOH increases the conversion energy barrier from * O to * OOH intermediates, inhibiting OER while improving urea oxidation reaction (UOR) activity. Hence, the catalyst almost completely suppresses OER and achieves ≈100% UOR selectivity, reaching a large urea electrolysis current density of 1.0 A cm −2 at a voltage of 1.88 V in the membrane electrode assembly. This study proposes an effective strategy for developing highly selective UOR catalysts by regulating competitive adsorption on active sites.