A urotropine-induced g-C3N4 membrane enhancing CO2 transition for robust and active urea-assisted water splitting

To address the kinetic limitations of CO2 desorption in the urea oxidation reaction (UOR), we develop a urotropine-induced strategy to engineer NiS–Ni3S2@g-C3N4 electrocatalysts. Urotropine, serving as both a structure-directing agent and g-C3N4 precursor, forms a dandelion-like architecture with narrowed columnar fluffs to maximize the surface area. The electronegativity difference between g-C3N4 and NiS–Ni3S2 induces local electron interactions, converting inactive sites to electron-enriched active sites and reducing adsorption energy barriers for CO2 desorption, the rate-limiting step. This catalyst exhibits outstanding UOR performance with a 1.24 V onset potential, 1.34 V to reach 100 mA cm−2, and 90% activity retention over 40 hours, while also demonstrating superior trifunctional activity rivaling IrO2 (OER: η10 = 90.9 mV) and Pt/C (HER: η10 = 13 mV). The urea electrolyzer requires only 1.26 V for 10 mA cm−2 with 48-hour stability. This work provides a breakthrough in designing efficient electrocatalysts through synergistic structural and electronic regulation.