Strain-dependent polaron regulation suppresses carrier decay in perovskite nanowires to enhance CO2 photoreduction.

Metal-halide perovskite nanocrystals, as efficient photocatalysts with unique properties, have attracted significant interest for various applications in energy and environmental catalysis applications. However, the full potential of metal-halide perovskite nanocrystals remains untapped. In this study, we synthesised a series of CsPbBr₃ nanowires with tailorable tensile strain (0%-1%) through a strain engineering approach to enhance photocatalytic CO₂ reduction performance. Nanowires with moderate strain (0.47%) attained superior catalytic performance with an electron consumption rate exceeding 300 μmol g^-1 h^-1 and 100% selectivity for CO production, surpassing that of the unstrained sample by five times. Ultrafast spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations revealed that the enhanced performance of the strained sample arises from strain-modulated polaron formation, which retards the carrier decay process (with the longest time component increasing from 672 ps to 2.85 ns), as well as strain-tailored electronic structures that lower the thermodynamic energy barrier for *COOH formation. Our study highlights the significance of strain-modulated polaron behaviour in metal-halide perovskite photocatalysts.