Oxygen vacancies induced by Ce3+/Ce4+ doping mediate the formation of Bi0/Bi2O3/Bi2O2.75 nanosheets for visible light-driven photocatalytic degradation of lignin

Fluorite bismuth oxide (δ-Bi2O3) has been extensively investigated in the fields of environmental and energy photocatalysis, owing to its exceptional charge transport performance and remarkable resistance to photocorrosion. However, the limited absorption spectrum of light and rapid recombination of photogenerated charge results in a low quantum efficiency. Herein, abundant oxygen vacancies Bi0/Bi2O3/Bi2O2.75 ultrathin nanosheets materials with a thickness of approximately 4.8 nm are constructed by Ce doping. It is shown that doping Ce in Bi2O3 lattice can generate oxygen vacancies, which induces phase transition rearrangement of δ-Bi2O3 to form tetragonal phase Bi2O2.75 locally, and finally forming Bi2O3/Bi2O2.75 heterojunction. In addition, the addition of Ce in the solvothermal process inhibits the conversion of Bi3+ to bismuth at high temperature, making the content of each component in the Bi0/Bi2O3/Bi2O2.75 heterostructure controllable. The optimized Bi0/Bi2O3/Bi2O2.75 catalyst exhibits excellent performance in visible light catalytic degradation of lignin, owing to the synergistic effect of high specific surface area, Bi plasma resonance effect and charge mobility. The degradation rate is approximately 35.0 times and 30.6 times higher than that of pure Bi2O3 and non-doped Bi/Bi2O3, respectively. Both the formation mechanism and S-type charge transfer mechanism of Bi0/Bi2O3/Bi2O2.75 heterojunction have been deeply analyzed through experimental investigation and DFT theoretical calculations.