Abstract: Carbon dioxide (CO₂) can be reduced to high-value fuels using the photocatalysis (PC) technique, which holds immense potential for tackling environmental issues and energy crises. The construction of metal-free photocatalyst capable of utilizing infrared light to execute thermal-assisted photocatalysis (TPC) remains a challenge. In this study, reduced graphene oxide (RGO) with full-spectrum absorption was used as a thermal-assisted photocatalyst in CO₂ reduction. It exhibited higher CO₂ reduction efficiency under the visible and infrared irradiation than the sole visible irradiation. RGO-5 (GO treated at 120 °C for 5 h) presented the highest defect density and C-OH/C-O-C content, leading to the best PC and TPC efficiencies. RGO was further engineered with HCl protonated g-C₃N₄ (H-CN) to obtain two-dimensional heterojunction RGO/H-CN, which demonstrated the S-scheme charge transfer process. Owing to the synergistic effect of heterojunction and thermal assistance, RGO/H-CN exhibited better CO₂ reduction efficiencies in both PC and TPC than RGO. The largest yields of CO and CH₄ were achieved in 15% RGO/H-CN. This research provides new insights for applying RGO as thermal-assisted heterojunction photocatalyst for efficient CO₂ reduction.

Key words: CO₂ reduction, Thermal-assisted photocatalysis, Heterojunction, Reduced graphene oxide, g-C₃ N₄