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

Platinum is one of the most efficient cocatalysts for photocatalytic reduction of carbon dioxide (CO 2 ) to methane (CH 4 ), but it still suffers from low CO 2 reduction rate and low selectivity of CH 4 . In this study, Pt/TiO 2 catalysts with adjustable Pt particle size (0.55-1.80 nm) were prepared by atomic layer deposition (ALD) and used for photocatalytic reduction of CO 2 to CH 4 . The CH 4 yield and selectivity of the Pt/TiO 2 catalysts showed a volcanic variation trend with the increase of Pt particle size. The 10Pt/TiO 2 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 CH 4 (product-based selectivity of 90.20%), and 100% for hydrocarbons (CH 4 , C 2 H 6 , and C 3 H 8 ) are achieved, no H 2 formation was detected. The CO-DRIFTS, XPS, CO 2 -TPD, H 2 O-TPD, and H 2 -TPD characterizations suggest that the 10Pt/TiO 2 exhibited optimal CO 2 adsorption/activation capacity, suitable H 2 O activation capacity, and higher hydrogen desorption temperature, making the generation rate of active hydrogen species from H 2 O matches their consumption rate for CO 2 hydrogenation. This study opens an avenue for rationally designing highly efficient and selective photocatalysts for photocatalytic CO 2 reduction.