Cu Atom-doped CsPbBr3 Nanocrystals for Enhanced Photocatalytic CO2 Reduction Reaction
Kuan-Chang Wu, Yu-Dian Chen, Yi-Chia Chen, Srimanta Das, Ishika Bhullar, Chia-Che Chang, Ying-Huang Lai, Soumitra Satapathi, Di-Yan Wang*
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 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 Cu element 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 that a partial reduction of Cu²⁺ in Cu-CsPbBr₃ PNCs. The results represented that the occurrence of photoexcited electron transfer from CsPbBr₃ to the doped Cu sites during 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 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.