Size regulation of Pt cocatalysts and its effect on the performance of photocatalytic CO2 transformation to CH4

Abstract

Platinum is one of the most efficient cocatalysts for photocatalytic reduction of carbon dioxide (CO₂) to methane (CH₄), but it still suffers from low CO₂ reduction rate and low selectivity of CH₄. In this study, Pt/TiO₂ catalysts with adjustable Pt particle size (0.55-1.80 nm) were prepared by atomic layer deposition (ALD) and used for photocatalytic reduction of CO₂ to CH₄. The CH₄ yield and selectivity of the Pt/TiO₂ catalysts showed a volcanic variation trend with the increase of Pt particle size. The 10Pt/TiO₂ with Pt particle size of 1.35 nm exhibit the highest methane yield (71.9 μmol/(g·h)). Especially, a high electron-based selectivity of 81.69% for CH₄ (product-based selectivity of 90.20%), and 100% for hydrocarbons (CH₄, C₂H₆, and C₃H₈) are achieved, no H₂ formation was detected. The CO-DRIFTS, XPS, CO₂-TPD, H₂O-TPD, and H₂-TPD characterizations suggest that the 10Pt/TiO₂ exhibited optimal CO₂ adsorption/activation capacity, suitable H₂O activation capacity, and higher hydrogen desorption temperature, making the generation rate of active hydrogen species from H₂O matches their consumption rate for CO₂ hydrogenation. This study opens an avenue for rationally designing highly efficient and selective photocatalysts for photocatalytic CO₂ reduction.