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.