Selectivity Modulated by Surface Ligands on Cu₂O/TiO₂ Catalysts for Gas-Phase Photocatalytic Reduction of Carbon Dioxide

We report gas-phase photocatalytic CO₂ reduction with Cu₂O/TiO₂ photocatalysts of varying surface passivation. With taurine adsorbed on the photocatalyst surface, the CH₄ production rate increases and CO production rate decreases compared to photocatalysts with no ligand treatment. When ethylenediamine is present on Cu₂O/TiO₂ photocatalysts, CO selectivity enhances significantly. In situ Fourier transform infrared spectroscopy and density functional theory calculation reveal that the surface ligands on the photocatalyst surface alter the binding strength of reaction intermediates (e.g., CO) on surface atoms of the photocatalysts. Our findings cast light on a new design principle for the catalyst surface in selective CO₂ conversion.