An in-situ spectroscopic study on the photochemical CO2 reduction on CsPbBr3 perovskite catalysts embedded in a porous copper scaffold

Photocatalytic CO2 reduction is a technology which converts carbon dioxide into high value-added chemicals, simultaneously resulting in a reduction of carbon dioxide and the production of useful chemicals. To increase the conversion efficiency and product selectivity, various parameters such as the light absorption efficiency, catalytic reaction activity on the electrode surface, and charge separation efficiency must be considered. In this study, photocatalytic CO2 reduction was investigated using an inorganic halide perovskite-based photocatalyst with a copper scaffold as a co-catalyst. We found that, when the two catalyst materials are used together, the photosensitized perovskite-based photocatalyst efficiently delivers excited electrons to the copper scaffold and produces a higher variety of products (for example, CH4, C2H4, and C2H6) than that without the copper scaffold. During photo-irradiation, a multi-scattering process occurs in the copper scaffold, which generates more photo-induced carriers, resulting in an enhanced light harvesting ability compared to that of the planar structure without the porous scaffold. Therefore, the CsPbBr3 perovskite catalysts embedded in a porous copper scaffold exhibit superior photocatalytic performance toward CO2 reduction. In the photocatalytic reduction reaction of CO2 on the perovskite photocatalyst with a copper scaffold, ethylene (C2H4, 46.5 μmol/g) was a major product and methane (CH4, 18.9 μmol/g), ethane (C2H6, 17.1 μmol/g), and propane (C3H8, 11.3 μmol/g) were additionally detected. On the other hand, the planar perovskite photocatalyst has very low catalytic activity for CO2 reduction and only methane (CH4, 17.2 μmol/g) was observed as a main conversion product from CO2 after light irradiation. Additionally, in this work, in-situ ATR-IR analysis was performed to understand the photocatalytic CO2 reduction mechanism.