High efficiency photocatalytic conversion of CO₂ with H₂O over Pt/TiO₂ nanoparticles

The objective of this research was to convert CO₂ to CH₄ using photocatalysis. In this investigation, well-crystallized anatase TiO₂ nanoparticles with diameters of ∼18.4 nm and a BET surface area of 108.3 m² g^-1 were synthesized by a solvothermal method and then Pt/TiO₂ nanocomposites with high photocatalytic performance and stability were prepared by photoreduction. The average diameter of the well-dispersed Pt nanoparticles was 1.82 nm. The optimal TiO₂ calcination temperature was 500 °C, while Pt photodeposition time was 1 h. The photoluminescence (PL) spectra demonstrated that the efficiency of photogenerated charge transfer and separation of Pt/TiO₂ was better than that of Pt/P25. For the optimized Pt/TiO₂ photocatalysts, the CH₄ yield reached 60.1 μmol/(g_cat h), together with a H₂ yield of 87.5 μmol/(g_cat h) and an C₂H₆ yield of 2.8 μmol/(g_cat h) at 4 h of irradiation. The photocatalytic CO₂ conversion ability of Pt/TiO₂ was 3.7 times that of Pt/P25. Longer irradiation would result in an increase of H₂ output, but not the output of CH₄ or C₂H₆. With 10.0% CO₂, the CH₄ yield and H₂ yield reached 54.4 μmol/(g_cat h) and 80.2 μmol/(g_cat h), respectively. O₂ was detected and recorded for a systematic analysis of the relationship between CO₂ conversion and water splitting. In addition, the photogenerated electron-hole balance was calculated and an associated reaction mechanism was proposed.