Z-Scheme Hydrothermal Carbonaceous Carbon/MoO₂ Heterojunction via One-Pot Synthesis for Photocatalytic H₂O₂...

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⁺, SO₄^2-) 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.