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

Abstract

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.