Polarization Induced by Chlorine Defect Engineering in High‐Entropy Halide Perovskite to Promote CO2 Photomethanation

The Coulomb electric field formed between positive and negative charges always restricts the generation and separation of photo-irradiated electrons and holes, resulting in the limited CO₂ photoreduction performances of catalysts. Herein, the defect engineering and high-entropy strategies are used to regulate the crystallinity of Cs₂NaInCl₆ perovskite materials, thus resulting in an enhanced internal polarization electric field, which overcame the Coulomb electric field and promoting the separation process of charge carriers. Moreover, the Cs₂Na{InPrSmGdTb}₁Cl₆ with Cl vacancies is prepared using the low-temperature syntheses, which overcame the challenge of extremely high-temperature requirements for high entropy alloy preparation. Compared with Cs₂NaInCl₆, Cs₂Na{InPrSmGdTb}₁Cl₆ with Cl vacancies contribute to an 8fold enhanced polarization electric field, suppressing the recombination of photogenerated electrons and holes and thus achieving an enhanced CO₂ photomethanation activity with improved product selectivity and structural stability. This work provides a promising strategy for designing and preparing low-temperature synthesizing modified high-entropy halide perovskite catalysts used in the field of solar energy conversion.