MXene quantum dots induced Ni site d-band center self-optimization for advanced photovoltaic-driven urea-assisted water splitting

Urea-assisted electrolytic water splitting for hydrogen production represents an effective contemporary strategy for generating green hydrogen. The sluggish kinetics of the anodic urea oxidation reaction (UOR) and cathodic hydrogen evolution reaction (HER) limit their practical application. The MXene quantum dots (MQDs) promote pronounced d-d orbital hybridization between Ni and Mo sites. The constructed heterostructures facilitate electron transfer and modulate charge redistribution. The extensive formation of heterostructures between numerous quantum dots and nickel molybdate results in the emergence of flower-like clusters at the tips of rod-like NiMoO 4 particles. The augmentation of the specific surface area results in the exposure of a larger quantity of active sites, which facilitates the redistribution of charge across these active sites, consequently enhancing the hydrolytic activity. The electrocatalyst exhibits remarkable performance in both the UOR and HER, achieving 1.31 V and 55 mV at 10 mA cm –2 , respectively. The catalyst for urea–assisted water electrolysis requires only 1.38 V at 10 mA cm –2 . The prepared catalyst can be employed for seawater splitting and photovoltaic-driven hydrogen production. In-situ Raman spectrum confirms that Ni sites on the NiMoO 4 /MQDs surface transform into Ni–OOH under hydrolysis and subsequently govern the hydrolytic reaction. This work indicates that d-d orbital hybridization can provide pathways for electronic transitions, thereby enhancing charge-transfer efficiency and effectively lowering reaction energy barriers.