Photothermal effect promoting CO2 conversion over composite photocatalyst with high graphene content

•A glucose-assisted solvothermal strategy is developed to fabricate TiO2-graphene.•The photothermal effect increased the surface temperature from 59 to 116 °C.•The optimized composite exhibits 5.1 times higher of CH4 evolution rate than TiO2.•The enhancement is due to the increased electron mobility and surface temperature.•The direct evidence of oxidation cycle presents complete understanding of mechanism.