Fabrication of TiO2-BiOBrxI1-x heterojunctions with adjustable band structure for enhanced visible light photocatalytic activity

Abstract TiO2-BiOBrxI1-x heterojunctions were systematically synthesized by a hydrothermal method, followed by a solvothermal route. BiOBrxI1-x solid solutions with controllably modulated band gaps were fabricated by altering the ratio of Br/I, and coupled closely with TiO2 nanorods (TiO2 NRs) to form heterojunctions with overlapping band structure. TiO2-BiOBrxI1-x with the optimal ratio of x = 0.75 displayed significantly enhanced photocatalytic activity towards Rhodamine B (RhB), compared to other TiO2-BiOBrxI1-x heterojunctions (x = 1, 0.5, 0.25, 0), BiOBr0.75I0.25 and TiO2 NRs by virtue of broadened visible light adsorption region, optimized redox potentials and accelerated carrier separation. The results demonstrated that solid solution fabrication and heterojunction construction played a synergistic role in improving photocatalytic performance in contrast to the single modification strategy. The enhancement mechanism and the synergistic effects were also elucidated on basis of band structure engineering and interface engineering. The joint utilization of multiple modification strategies is significantly instructive for the design and synthesis of highly efficient photocatalysts for practical application in the fields of environment and energy.