Abstract:
Platinum is one of the most efficient cocatalysts for photocatalytic reduction of carbon dioxide (CO
2) to methane (CH
4), but it still suffer 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
2H
6, and C
3H
8) are achieved, no H
2 formation was detected. The CO-DRIFTS, XPS, CO
2-TPD, H
2O-TPD, and H
2-TPD characterizations suggest that the 10Pt/TiO
2 exhibited optimal CO
2 adsorption/activation capacity, suitable H
2O activation capacity, and higher hydrogen desorption temperature, making the generation rate of active hydrogen species from H
2O 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.