High methane selective Pt cluster catalyst supported on Ga2O3 for CO2 hydrogenation

In heterogeneous catalysis, the CO2 hydrogenation reaction is an important class of reactions that has been widely studied for decades. Particularly, the particle size of the metal plays a crucial role in controlling the selectivity of the CO2 hydrogenation reaction. However, there have only been a few studies investigating the selectivity for sub-nanometer sized particles. Here, we report the effect of Pt particle size on the catalytic activity and selectivity of CO2 hydrogenation. The size of the Pt particles was tuned by changing the amount of loading. With low Pt loading on gallium oxide, Pt clusters were formed; however, Pt nanoparticles were synthesized with high Pt loading. The Pt clusters were mainly edge and step sites where CO2 adsorbs more strongly, while the Pt nanoparticles were mainly composed of terrace sites. The catalytic performance of the Pt catalysts was examined using CO2 hydrogenation. The Pt clusters showed a higher methane selectivity than that of the Pt nanoparticles. The reaction mechanism was analyzed by diffuse reflectance infrared fourier transform (DRIFT) spectroscopy at reaction conditions. The Pt clusters mainly showed the formate peak, while showing fewer carbonate peaks than the support. These results suggest that the formation of CH4 follows the formate route.