pH-controlled Pt valence states modulation over Pt/g-C3N4 for highly active photocatalytic CO2 methanation at room-temperature

Pt 2 + - and Pt 4+ -loaded g-C 3 N 4 (Pt/CN) catalysts were synthesized for the reduction of CO 2 to CH 4 at room temperature (25 °C) by adjusting the solution pH during the photodeposition process. Acidic conditions (pH = 4) favored the formation of Pt 2+ , while Pt 4+ was the predominant species under alkaline conditions (pH = 10) in the Pt/CN photocatalyst . A strong electronic metal-support interaction between Pt and N atom was constructed, enhancing charge transfer from N to Pt. Pt 2+ exhibited superior electron-trapping capabilities. The influence of Pt species on the bandgap of Pt/CN photocatalyst was minimal, but the positions of the conduction band and valence band changed significantly. An increased presence of Pt 2+ resulted in a more negative valence band position and improved separation efficiency of photogenerated carriers , which enhances the reactivity of photocatalytic CO 2 -to-CH 4 reduction process. Furthermore, the amount of Pt loading played a crucial role in the photocatalytic performance for CO 2 methanation . Consequently, the as-prepared 3 %-Pt/CN-4 photocatalyst (3 wt% Pt content, pH = 4) demonstrated the highest photocatalytic activity for CO 2 -to-CH 4 conversion, achieving a rate of 11.69 μmol·g −1 ·h −1 under xenon lamp AM1.5 G light irradiation at 25 °C. • pH-driven Pt 2+ /Pt 4+ modulation enhances CO 2 methanation at room temperature. • Acidic condition favors Pt 2+ formation. • Pt 2+ enhances photogenerated carriers separation efficiency. • 3 %-Pt/CN-4 photocatalyst achieves 11.69 μmol·g −1 ·h −1 CH 4 yield. • Strong Pt-N interaction optimizes band structure and charge separation.