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.