Molecule-Driven Shape Control of Metal Co-Catalysts for Selective CO2 Conversion Photocatalysis

In photocatalysis of CO2 conversion, metal co-catalysts draw photo-generated electrons from semiconductor components and act as reaction sites by adsorbing CO2 and its intermediates. Optimization of the metal co-catalyst structure is indispensable to improving the efficiency of the photocatalyst, which is currently not meeting performance requirements. By performing a series of experiments and simulations, we demonstrate the effect of selective particle shape control of metal co-catalysts (Au, Ag, Cu and Pt) by the CO2 induced gas ligands (CO2 and CO) on photocatalytic CO2 conversion activity and selectivity. Indeed, facet formation for adsorption of CO2 and CO proves to be an effective way to improve the CO2 conversion activity. In particular, proper interaction between the gas ligand and the metal co-catalyst surface, realized by strengthening the metal-CO2 adsorption and weakening the metal-CO adsorption, is identified as essential factor for increasing the CO2 conversion activity. Pt and Cu, which exhibit relatively strong interaction with gas molecules, have the improved photocatalytic CO2 conversion activity when grown under CO2. In contrast, Au and Ag, which exhibit relatively weak interaction with gas molecules, have the enhanced photocatalytic CO2 conversion activity when grown under CO. This systematic understanding can be a guideline for controlling the metal co-catalyst surface structure and will maximize the photocatalytic selectivity of the CO2 conversion.