Size-dependent selectivity and activity of highly dispersed sub-nanometer Pt clusters integrated with P25 for CO2 photoreduction into methane fuel

Integration of sub-nanometer-sized Pt cocatalysts on semiconductor materials is a promising approach to improve the activity and selectivity of CO2 photoreduction. However, the practical realization of such an integrated catalyst is a challenging task. We rationally integrated sub-nanometer Pt nanoclusters (Pt NCs) on the surface of commercial P25 catalyst by adjusting the amount of Pt loading. The lateral reduction in the size of Pt NCs resulted in high metal dispersion, increased active metal surface area, better CO2 adsorption, and hindered photoexcited charge-carrier recombination. The sub-nanometer Pt NCs integrated with P25 with a weight percentage of 0.5% (Pt-NC/P25-0.5) exhibited exceptional CO2 photoreduction activity for CH4 production and excellent stability during successive test runs. This catalyst outperformed its counterparts with larger Pt NCs and several previously reported state-of-the-art photocatalysts in terms of CH4 generation. Importantly, compared to its counterparts, Pt-NC/P25-0.5 had a higher proportion of edge and corner sites, which have a strong affinity for CO molecules, resulting in a high CH4 selectivity of 95% against H-2. The size-dependent selectivity and activity of Pt NCs for CO2 reduction demonstrated in this study offer insights into the development of sub-nanometer metal based catalysts for photocatalytic energy applications.