Regulating the spin state of single Fe atom in BiOBr to enhance photocatalytic nitrogen reduction: insights from theoretical studies

Abstract

Herein, we investigated the effects of the Fe spin state on nitrogen reduction reaction (NRR) in BiOBr, using density functional theory. Our simulations reveal that P doping can reduce the Fe spin state. This leads to an overlap of orbitals between N2 and Fe atom at the Fermi energy level, thereby promoting the activation of N2. The investigation of NRR mechanisms reveals that the enzymatic mechanism is more favorable over the distal and alternating mechanisms. The formation of NNH with an energy barrier of 2.32 eV is identified as the rate-determining step for the NRR process in the Fe-doped BiOBr system. Furthermore, P doping dramatically reduces the energy barrier of the rate-determining step, which involves releasing the second NH₃ molecule, by a factor of 2.37. This study elucidates the influence mechanism of the Fe spin state on the performance of NRR, providing valuable theoretical guidance for designing highly efficient photocatalysts.