Novel through-holes g-C3N4/BiOBr S-scheme heterojunction: Charge relocation mechanism and DFT insights

Abstract

A novel multiscale through-holes g-C3N4/BiOBr S-scheme heterojunction with homogeneous morphology was fabricated via a solvothermal method. Notably, the prepared through-holes g-C3N4 yielded a subband gap (2.11 eV) attributed to the fracture and reorganization of triazine ring units, leading to a narrow band gap complex. Photocatalyst A-2 (2.73 eV) was significantly broadened at the absorption edge. A reasonable S-scheme heterojunction charge relocation mechanism was demonstrated based on active species trapping experiments, atomic force microscope (AFM) equipped with a Kelvin probe force microscope (KPFM), and density functional theoretical (DFT) theoretical calculations. The S-scheme g-C3N4/BiOBr heterojunction and the constructed internal electric field facilitate the retention of high redox properties and facilitated charge relocation. Hence, the synergistic interaction between the S-scheme heterojunction and through-holes structure enabled specimens to be exhibited high-efficiency degradation activity. The degradation efficiency of photocatalyst A-2 for TC·HCL and RhB was 94.5% (60 min) and 99.9% (30 min), respectively. At pH = 5.1, the TC·HCL photoreaction time was reduced to 30 min, whereas at pH = 2.3, the RhB photoreaction time was shortened to 15 min. Five repeatable recovery tests still maintain excellent stability. This work contributes new insights into the charge relocation mechanism of S-scheme heterojunction high-efficiency photocatalysts.