Improving the Catalytic CO(2) Reduction on Cs(2)AgBiBr(6) by Halide Defect Engineering: A DFT Study

Pb-free double halide perovskites have drawn immense attention in the potential photocatalytic application, due to the regulatable bandgap energy and nontoxicity. Herein, we first present a study for CO(2) conversion on Pb-free halide perovskite Cs(2)AgBiBr(6) under state-of-the-art first-principles calculation with dispersion correction. Compared with the previous CsPbBr(3), the cell parameter of Cs(2)AgBiBr(6) underwent only a small decrease of 3.69%. By investigating the adsorption of CO, CO(2), NO, NO(2), and catalytic reduction of CO(2), we found Cs(2)AgBiBr(6) exhibits modest adsorption ability and unsatisfied potential determining step energy of 2.68 eV in catalysis. We adopted defect engineering (Cl doping, I doping and Br-vacancy) to regulate the adsorption and CO(2) reduction behavior. It is found that CO(2) molecule can be chemically and preferably adsorbed on Br-vacancy doped Cs(2)AgBiBr(6) with a negative adsorption energy of −1.16 eV. Studying the CO(2) reduction paths on pure and defect modified Cs(2)AgBiBr(6), Br-vacancy is proved to play a critical role in decreasing the potential determining step energy to 1.25 eV. Finally, we probe into the electronic properties and demonstrate Br-vacancy will not obviously promote the process of catalysis deactivation, as there is no formation of deep-level electronic states acting as carrier recombination center. Our findings reveal the process of gas adsorption and CO(2) reduction on novel Pb-free Cs(2)AgBiBr(6), and propose a potential strategy to improve the efficiency of catalytic CO(2) conversion towards practical implementation.