Photocatalytic CO2 conversion to chemical fuels represents a promising approach to alleviate energy shortage and greenhouse effect. Graphene has been extensively employed in fabricating composite photocatalysts due to its excellent conductivity, however another important property as a photothermal material has not been valued enough so far. Here, a remarkable photothermal effect is discovered in the optimized TiO2-graphene composite and demonstrated to have great impact on the photocatalytic CO2 conversion based on the temperature-dependent kinetic analysis which has not been studied previously. The synergetic effect of the increased electron mobility and surface temperature dramatically enhanced the photocatalytic efficiency. More importantly, the enhanced efficiency enables the quantitative oxygen measurement, which provides the direct evidence of oxidation cycle that is seldom achieved in the literatures. This study not only reveals the important role of photothermal characteristic of graphene-based photocatalysts in promoting CO2 conversion but also presents complete understanding of the overall photocatalytic mechanism. (C) 2019 Elsevier Inc. All rights reserved.