Regulation of excitation energy transfer in Sb-alloyed Cs4MnBi2Cl12 perovskites for efficient CO2 photoreduction to CO and water oxidation toward H2O2

Lead (Pb)-free halide perovskites have recently attracted increasing attention as potential catalysts for CO2 photoreduction to CO due to their potential to capture solar energy and drive catalytic reaction. However, issues of the poor charge transfer still remain one of the main obstacles limiting their performance due to the overwhelming radiative and nonradiative charge-carrier recombination losses. Herein, Pb-free Sb-alloyed all-inorganic quadruple perovskite Cs4Mn(Bi1−xSbx)2Cl12 (0 ≤ x ≤ 1) is synthesized as efficient photocatalyst. By Sb alloying, the undesired relaxation of photogenerated electrons from conduction band to emission centers of [MnCl6]4− is greatly suppressed, resulting in a weakened PL emission and enhanced charge transfer for photocatalyst. The ensuing Cs4Mn(Bi1−xSbx)2Cl12 photocatalyst accomplishes efficient conversion of CO2 into CO, accompanied by a surprising production of H2O2, a high value-added product associated with water oxidation. By optimizing Sb3+ concentration, a high CO evolution rate of 35.1 μmol g−1 h−1 is achieved, superior to most other Pb and Pb-free halide perovskites. Our findings provide new insights into the mixed-cation alloying strategies for improved photocatalytic performance of Pb-free perovskites and shed light on the rational design of robust band structure toward efficient energy transfer.