The team addressed a persistent limitation in photocatalysis: the fast recombination of light-generated electrons and holes that reduces reaction efficiency. They engineered cesium lead bromide (CsPbBr3) nanowires with uniform tensile strain by inducing a mismatch with a secondary cesium lead pentabromide (CsPb2Br5) phase. By adjusting strain between 0% and 1%, they identified an optimal level of 0.47%, which yielded approximately 150.2 micromoles of CO per gram per hour with complete selectivity and excellent long-term stability.
Advanced spectroscopy and density functional theory calculations revealed why strain boosts performance. The controlled distortion enhances polaron formation, slowing electron-hole recombination. In optimally strained nanowires, carrier decay lifetimes extended from 672 picoseconds to 2.85 nanoseconds. Strain also shifted the energy of lead p-orbitals upward, strengthening interactions with reaction intermediates and lowering the barrier for forming the critical *COOH step in CO2 reduction.
"This work provides profound insights," said corresponding author Jianping Sheng. "We demonstrate that strain engineering is a powerful tool not just for tweaking electronic properties, but for fundamentally controlling polaron behavior - a key determinant of charge dynamics in soft lattice materials like perovskites. This opens exciting new avenues for designing highly efficient photocatalysts and electrocatalysts."
The findings position strained perovskite nanowires ahead of many state-of-the-art photocatalysts, underscoring the promise of strain engineering for advancing solar fuel technology.
Research Report:Strain-dependent polaron regulation suppresses carrier decay in perovskite nanowires to enhance CO2 photoreduction
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