Cooperative phosphorus and chromium doping induced electronic and morphological dual modulation in NiMoO4 hydrate for energy-efficient urea-assisted hydrogen production

The electrochemical oxidation of urea presents a promising avenue for hydrogen production with reduced energy consumption. Therefore, developing an efficient bifunctional electrocatalyst capable of catalyzing both the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is of prominent importance. Herein, a cooperative P and Cr co-doped NiMoO4 hydrate electrode (P/Cr60-NiMoO4) is developed as a self-supported bifunctional electrode for energy-efficient urea-assisted H2 production. Benefiting from the cooperativity of both dopants, the P/Cr60-NiMoO4 electrocatalyst exhibits remarkable performance in UOR and HER, achieving 1.33 V and 35.7 mV at 10 mA cm−2, respectively. Moreover, the utilization of P/Cr60-NiMoO4 as a dual-functional catalyst only needs 1.35 V to reach 10 mA cm−2 in 1 M KOH electrolyte with 0.33 M urea, representing a reduction of 180 mV compared to conventional water electrocatalysis devices (OER//HER systems). Theoretical calculations based on density functional theory reveal that the superior activity of the P/Cr-incorporation system can be attributed to its ability to enhance interface electron concentration, promote electron transfer, and reduce the free energy barriers associated with both UOR and HER.