Synthesis of small size lead-free Cs3Bi2xSb2−2xBr9 solid-solutions using a spatially confined growth method for efficient photocatalytic CO2 reduction

Abstract

The sustainable reduction of CO₂ to chemical fuels through photocatalysis is a promising research direction. However, most photocatalysts still face the issues of narrow light absorption, small specific surface area, and poor charge separability. Herein, Cs₃Bi_2xSb_2−2xBr₉ (CBSB-X) solid solutions with good visible light absorption are successfully prepared. Moreover, small-sized CBSB-X nanoparticles can be obtained by spatially confined growth of CBSB-X in MCM-41 molecular sieve. The MCM-41@CBSB-X samples with a large specific surface area and efficient carrier transport demonstrate excellent photocatalytic CO₂ reduction to CO activity. In the gas–solid reaction system irradiated by visible light, the optimal MCM-41@Cs₃Bi_0.6Sb_1.4Br₉ (MCM-41@CBSB-0.3) composite shows an excellent photocatalytic activity with a CO yield of 11.2 μmol g⁻¹ h⁻¹, which is 5.9 and 15.1 times higher than that of bulk CBSB-0.3 and Cs₃Bi₂Br₉ (CBB), respectively. Temperature programmed desorption measurement proves that the MCM-41@CBSB-0.3 composite promotes CO₂ adsorption compared to bulk CBSB-0.3. The gradually generated COOH* intermediate detected by in situ infrared spectroscopy is the reason for the high selective CO production. This work provides a new idea for the synthesis of small-sized perovskites, which inspires the design and application of other lead-free perovskites in photocatalysis.