Photocatalytic CO2 Conversion Using MoSe2/g-C3N4 Heterostructured Composites with Enhanced Selectivity and Activity

The photocatalytic conversion of CO2 into value-added hydrocarbons offers a sustainable route for mitigating carbon emissions. In this study, we synthesized MoSe2/g-C3N4 heterostructured composites through a hydrothermal method and used these composites in the photocatalytic reduction of CO2 in the presence of ultraviolet radiation. Photoluminescence characterization, photocurrent analysis, and electrochemical impedance spectroscopy confirmed improved charge separation and interfacial transfer as a result of the composites’ heterojunction structure. The MoSe2/10 wt% g-C3N4 composite exhibited a CH4 production rate of 1.38 μmol g−1 h−1 and a CO2 consumption rate of 2.22 μmol g−1 h−1, which are 4.2 and 3.1 times, respectively, higher than those of pure MoSe2. Gas chromatography revealed the selective formation of C1–C5 hydrocarbons, with minimal oxygenated by-products. Band structure analysis conducted through ultraviolet photoelectron spectroscopy and ultraviolet–visible/near-infrared spectroscopy confirmed the proposed charge transfer pathway and enhanced C–C coupling efficiency. Overall, these results demonstrate the potential of the as-prepared heterojunction composites for highly selective CO2-to-CH4 conversion under mild conditions, with CH4 as the dominant product (80%) among the generated hydrocarbons.