Cu-Atom-Doped CsPbBr 3 Nanocrystals for Enhanced Photocatalytic CO 2 Reduction Reaction

Photocatalytic CO2 reduction (CO2RR) is particularly attractive due to its ability to directly harvest solar energy, representing a promising and sustainable route toward carbon neutrality. All-inorganic halide perovskite nanocrystals, such as CsPbBr3, have emerged as highly promising photocatalysts owing to their exceptional electronic and optical properties. In this work, Cu-atom-doped CsPbBr3 perovskite nanocrystals (Cu-CsPbBr3 PNCs) were successfully developed, and the role of the Cu single atom in CsPbBr3 PNCs for modulating their photocatalytic CO2RR was elucidated. Comprehensive structural characterizations, including X-ray diffraction (XRD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and X-ray absorption spectroscopy (XAS), collectively confirm that the Cu element is atomically distributed as single atoms uniformly within the nanocrystal lattice rather than undergoing phase segregation into clusters or long-range-ordered Cu phases. A slight red shift of the Cu K-edge XANES under illumination was found, indicating a partial reduction of Cu2+ in Cu-CsPbBr3 PNCs. The results represented the occurrence of photoexcited electron transfer from CsPbBr3 to the doped Cu sites during the CO2RR. Moreover, photocatalytic CO2RR revealed that an optimal Cu-doping concentration in Cu-CsPbBr3 PNCs achieves a significantly enhanced CO production rate of 2.80 μmol g-1 h-1, outperforming pristine CsPbBr3 (1.47 μmol g-1 h-1). Time-resolved photoluminescence (TRPL) measurements show a substantial decrease in carrier lifetime from 3.17 ns (pristine CsPbBr3 PNCs) to 0.72 ns (optimal Cu-CsPbBr3 PNCs), evidencing efficient electron trapping by single Cu single atoms. Transient absorption (TA) spectra further reveal modified hot-carrier dynamics and pronounced carrier-trapping behavior. Overall, the enhanced photocatalytic activity of Cu-CsPbBr3 PNCs toward CO2 reduction is attributed to efficient nonradiative charge transfer from photoexcited CsPbBr3 PNCs to the dopant Cu atoms. This design strategy opens a general avenue for the development of metal-atom-doped perovskite-based photocatalysts with improved efficiency for the CO2 reduction reaction.