Synergistic engineering of doping and vacancy guiding transformation of active phase for efficient urea electrooxidation

The surface dynamic reconstruction of Ni-based catalysts can lead to the transformation into Ni-based active phase (NiOOH) for boosting the urea oxidation reaction (UOR), while a key challenge associated with Ni-based UOR catalysts is the difficulty in triggering and controlling the reconstruction process to achieve the highest catalytic activity, selectivity, and stability. Herein, oxygen-vacancy enriched and molybdenum doped NiCo layered double hydroxide (Mo-NiCo LDH-O_v) are prepared and employed as model to synergistically boost the UOR. The introduction of oxygen vacancies facilitates the formation of active phases of NiOOH and CoOOH, thus efficiently modulating the electronic configuration of its surface. Meanwhile, Mo doping induces an electronic regulation effect that promotes the oxidation of Ni and Co to higher valence states, accelerates the reaction kinetics, and enables the generation of a highly active composite phase (NiOOH–CoOOH–MoOₓ). The modified catalyst exhibits excellent UOR performance, requiring only 1.32 V (vs. RHE) to achieve a current density of 10 mA·cm⁻² in 1 M KOH with 0.33 M urea. This value is 284 mV lower than that needed for water oxidation. As a promising UOR catalyst, synergistic engineering of doping and oxygen vacancy Mo-NiCo LDH-O_v offers new design insights for urea oxidation and degradation.