Thermal coupled photocatalysis over Pt/g-C₃N₄ for selectively reducing CO₂ to CH₄ via cooperation of the electronic metal–support interaction effect and the oxidation state of Pt

Pt nanoparticle-loaded g-C₃N₄ (Pt/CN) that consisted of integrating Pt⁰ and Pt²⁺ species was prepared for selectively reducing CO₂ to CH₄ with H₂O by thermal coupled photocatalysis. A strong electronic metal-support interaction was constructed between Pt nanoparticles and the g-C₃N₄ substrate, which limited the activity for CO evolution and improved the charge transfer from g-C₃N₄ to Pt for selective CH₄ production. The formed Pt²⁺ species in the Pt nanoparticles completely suppress the side reaction of H₂ production from reducing H₂O. Moreover, a moderate heat input in the photocatalytic reaction facilitated the transfer of the photogenerated electrons from Pt nanoparticles to CO₂, which further increased the photocatalytic activity for CH₄ evolution. As a result, a significant enhancement of CO₂ methanation performance (∼100 % selectivity, 14.8 μmol g⁻¹ h⁻¹) was realized on a 2 % Pt-loaded g-C₃N₄ photocatalyst under low intensity light-emitting diode (420 nm, on the order of solar intensity) irradiation at 125 °C.