Photochemical CO2 Reduction Using a Lead-Free Cs2AgMCl6 (M= Bi, In, and Sb) Double Perovskite toward Selective Formic Acid Production

Abstract

Perovskite materials have been identified as promising photocatalysts for CO₂ reduction due to their unique physicochemical and optical characteristics. This study employs lead-free halide double perovskites based on Cs₂AgMCl₆ (M–Bi, In, and Sb or their mixed composition) as photocatalysts for carbon dioxide reduction. It was found that double perovskite materials are highly selective toward formic acid production, with more than 80% selectivity. The Cs₂AgInCl₆ material shows the best performance, with a formic acid conversion of 85.5 μmol g^–1 h^–1. These materials show excellent structural stability over 24 h under photocatalytic conditions. Furthermore, the selectivity of the product was investigated using density functional theory calculations, and the results show a low free-energy barrier toward the formation of formic acid as compared to other reduction products, including carbon monoxide and methane. The Ag site of the [110] terminated surface is identified to be a favorable site for catalytic reduction.