Cobalt doping modulation of Cs4MnBi2Cl12 double perovskite induces spin polarization for boosting photocatalytic reduction of CO2

Lead-free halide double perovskites (LFHDPs) show great potential for solar-to-fuel conversion due to their unique photoelectrochemical properties, but they suffer from easy carriers recombination and insufficient active sites. In this work, a series of Co-doped Cs 4 MnBi 2 Cl 12 (denoting as Cs 4 MnCo x Bi 1-x Cl 12 ) microcrystals were synthesized for CO 2 photocatalytic reduction. Results of various characterizations, Kelvin probe microscopy mode (KPFM) and density functional theory simulation (DFT) calculations showed that Co doping into the Cs 4 MnBi 2 Cl 12 could induce spin polarization, resulting in fast carriers separation and extending carriers lifetime. The Cs 4 MnCo 0.9 Bi 0.1 Cl 12 (CMC 0.9 B 0.1 C) microcrystals exhibited the CO yield of 69.16 μmol·g −1 ·h −1 , which was 177 times of that of CMBC (0.39 μmol·g −1 ·h −1 ). Notably, CO 2 reduction performance from the CMC 0.9 B 0.1 C was significantly enhanced by applying an external magnetic field (300 mT) to the system, with CO yield reaching 99.96 μmol·g −1 ·h −1 . The main intermediates during CO 2 reduction were carboxylate (COOH*) and chelating-bridged carbonate (C-CO 3 2− ), and CO 2 reduction pathways and mechanism were proposed accordingly. These findings highlight the great potential of Co-doped Cs 4 MnCo x Bi 1-x Cl 12 as a promising photocatalyst for light-driven CO 2 reduction, opening up new avenues for the development of LFHDPs-based photocatalytic system.