Spontaneous Urea-to-Water Electrolysis Driven by Anion Engineered Catalysts for Continuous Urea Treatment and...

UOR/OER bifunctional catalysts are essential to environmental remediation and hydrogen production from industrial wastewater with varied urea concentrations. Although a few studies attempt on catalysts with adaptive active centers for varying urea concentration, urea decomposition is inhibited when urea is adsorbed on OER-active phase with UOR-inertness. It can result in incomplete urea removal and passivated OER. In this work, carbonate-modified NiCo-γ-NiOOH was synthesized by utilizing the UOR byproduct CO₃ ^2-, which increased density of states at Fermi level and consequently formed UOR/OER bifunctional active phase. As a result, the catalyst only required 1.360 and 1.592 V vs. RHE for UOR and OER at 100 mA cm^-2, respectively, which also realized continuous urea-to-water electrolysis via spontaneous transition and gradual shift from UOR-dominating to OER-dominating electrolysis. Moreover, complete urea removal at the end implied the capability of the bifunctional active phase for sustained urea decomposition, thus mitigating the issue of residual urea and passivated OER. Density functional theory simulation indicated that CO₃ ^2- modification facilitated the deprotonation in UOR and *OOH intermediate formation in OER, thus enhancing bifunctional catalytic performance. This work presents a feasible strategy for complete urea removal and continuous hydrogen production via boosting both UOR and OER aided by anion engineering.