Photocatalytic reduction of CO₂ offers a promising approach to storing energy from intermittent sunlight in carbon-containing fuels and chemicals, thereby enabling carbon recycling. Single-atom Cu catalysts have attracted attention because they enhance CO₂ photoreduction. However, the roles of single-atom active sites and adjacent atoms in these catalysts have not been well understood.

Now, a new study published in Chem Catalysis has revealed how dynamic Cu and Ti active sites in single-atom Cu-TiO₂ catalysts cooperate under light to reduce CO₂ to CO.

The researchers, led by Prof. BI Yingpu and WANG Kangkang from the Lanzhou Institute of Chemical Physics (LICP) of the Chinese Academy of Sciences (CAS), conducted an experimental study of the dynamic interactions of CO₂ and H₂O molecules at the surface active sites of single-atom Cu-TiO₂ catalysts by integrating in-situ X-ray photoelectron spectroscopy with infrared spectroscopy.

They found that single-atom Cu and adjacent Ti sites play distinct roles during CO₂ photoreduction. Specifically, H₂O adsorption and electron injection at single-atom Cu sites promote CO₂ adsorption and activation at adjacent Ti sites, and their cooperative catalysis significantly improves CO₂-to-CO conversion efficiency.

They further found that single-atom Cu-TiO₂ exhibits substantially enhanced activity for CO₂-to-CO conversion (161.1 μmol g^-1 h^-1) relative to pristine TiO₂ (31.8 μmol g^-1 h^-1).

"These experimental findings challenge the conventional speculations on single-atom Cu catalysts and provide new insights for the re-evaluation of static structure–activity models," said BI.

Schematic illustration of the photocatalytic process of CO₂ reduction over the Cu-TiO₂ catalysts. (Image by LICP)