Z-Scheme Hydrothermal Carbonaceous Carbon/MoO ₂ Heterojunction via One-Pot Synthesis for Photocatalytic H ₂ O ₂ Production from Seawater

Utilizing inexhaustible seawater for the photocatalytic H2O2 production presents a significant challenge but offers a promising path toward sustainable energy. Herein, a Z-scheme MoO2-hydrothermal carbonaceous carbon (HTC) heterostructure was developed by a facile one-pot hydrothermal strategy for photocatalytic H2O2 production from seawater. The one-pot synthesis enables intimate MoO2/HTC interfacial contact, which creates efficient charge migration pathways and significantly enhances charge separation. The optimal MoO2/HTC material yielded a remarkable H2O2 production rate of 1078 μmol·g–1·h–1 in natural seawater (859 μmol·g–1·h–1 in ultrapure water). This superior activity arises from efficient charge separation and the robust redox capability of the Z-scheme heterostructure, as well as the favorable effects of certain ions (Mg2+, Na+, SO42–) in seawater on charge transfer. Ultraviolet photoelectron spectroscopy (UPS) characterization confirmed the formation of an internal electric field, which is induced by the Fermi level difference between the two materials. Moreover, zeta potential analysis and coexistence ion experiments demonstrated that MoO2 loading on HTC enhanced H2O2 photoproduction in seawater, which is attributed to the improved utilization efficiency of •O2–. Our findings provide crucial mechanistic insights that set the stage for designing next-generation Z-scheme catalysts capable of efficiently producing H2O2 directly from seawater.