Colloidal Synthesis of Palladium Nanocluster‐Decorated Cs 3 Sb 2 Cl 9 Perovskite Heterostructural Nanorods for Enhanced CO 2 Photoreduction

ABSTRACT Developing efficient and sustainable photocatalysts for CO 2 reduction remains a significant challenge, particularly with environmentally benign materials. Here, we report the first one‐step synthesis of metal–lead‐free perovskite heterostructural nanocrystals by decorating Cs 3 Sb 2 Cl 9 perovskite nanorods with size‐controlled Pd nanoclusters via a one‐step hot‐injection method. The resulting Pd‐Cs 3 Sb 2 Cl 9 heteronanorods (HNRs) exhibit strong interfacial electronic coupling, enhanced charge separation, and excellent colloidal stability. Transient absorption spectroscopy and DFT calculations reveal a built‐in electric field that drives directional electron transfer from the perovskite host to the Pd domains. Under UV irradiation, the Pd‐Cs 3 Sb 2 Cl 9 HNRs demonstrate excellent CO 2 photoreduction activity with high CH 4 selectivity, achieving a record apparent quantum yield (AQY) of 2.62% among halide perovskite nanocrystal‐based systems with a large electronic yield of 689.3 ± 12.2 µmol·g cat −1 . In situ spectroscopic monitoring and Gibbs free energy analysis further unveil a Pd‐facilitated reaction pathway involving stabilization of key intermediates. This work introduces a new class of lead‐free perovskite‐based heterostructures through a facile one‐step synthesis strategy and offers a new design principle for next‐generation photocatalysts for solar fuel production.