Theoretical insights into electronic structure and NRR catalytic mechanism based on halide perovskites CsPbBr3-xIx

The halide perovskites (CsPbBr3-xIx) with excellent photoelectric properties can be used as electrocatalysts for nitrogen reduction reaction (NRR). Their electronic structures and activation mechanism of the adsorbed species for N2-to-NH3 based on CsPbBr3-xIx (x = 0, 1, 2, 3) have been investigated using first principle calculations based on density functional theory (DFT). The calculated results reveal that CsPbBr3-xIx system can keep the stable perovskite structure as the tolerance factors (t) are 0.8621, 0.8583, 0.8546 and 0.8512 for x = 0, 1, 2 and 3, respectively. The stability, ionic property and energy gap values of CsPbBr3-xIx perovskite decrease with the increase of I doping amount. CsPbBr2I and CsPbBrI2 display the suitable d-band center (−1.792 eV and −1.8311 eV), the lower Gibbs free energy (1.16 eV and 1.13 eV), and the smaller overpotential (η = 1.00 eV and 0.97 eV) for the pronation of *N2 to produce *N2H species, which is the rate-determining step for the NRR. The DFT results indicate the order of NRR performance is CsPbBrI2 > CsPbBr2I > CsPbI3 > CsPbBr3. Compared the alternative, enzymatic and distal reaction paths based on the catalyst of CsPbBrI2 [1 0 0], the distal path has the lowest energy barrier, and it can be concluded that the distal path would be the feasible NRR reaction mechanism for CsPbBr3-xIx system.