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.