Enhanced Photocatalytic Hydrogen Evolution Via Efficient Electron Transfer Mechanism in Ni/NiO/CeO₂/MoS₂-MoO₃ Heterostructures Under UV Light Irradiation

NiO/CeO2/MoS2-MoO3 heterostructured photocatalysts were synthesized via a hydrothermal method and evaluated for photocatalytic hydrogen evolution from formic acid under UV and visible light irradiation. The design strategy integrated oxygen vacancies in CeO2, sulfur vacancies in MoS2, and the electron-trapping capacity of Ni/NiO to enhance charge separation and light harvesting. Four compositions (NCM-145, NCM-334, NCM-352, NCM-523) with varied Ni, CeO2, and MoS2/MoO3 mass ratios were comprehensively characterized using TEM, SAED, XRD, UV-DRS, PL, Raman, and XPS analyses. Among these, NCM-334 (3 wt% Ni / 3 wt% CeO2 / 4 wt% MoS2) achieved the highest hydrogen production rate (386 mu mol g(-)(1) h(-)(1)) under UV light, sustained notable activity under visible light, and exhibited an optimal band gap (3.17 eV), high crystallinity, and efficient electron-hole separation. PL confirmed reduced recombination, and XPS verified the presence of Ni-2(+), Ce-4(+)/Ce-3(+), and Mo-4(+)/Mo-6(+) species contributing to redox activity. The optimized NCM-334 achieved a conversion of 91.7% and selectivity of 94.4%, underscoring the critical role of compositional tuning in heterostructure catalysts for sustainable hydrogen production from formic acid.