Ultrathin sillenite nanosheets with wide-spectrum response and high photocatalytic oxidation performance

Abstract

Herein, we present a novel approach to synthesize ultrathin sillenite nanosheets (Bi₁₂(MO₄)_xO₁₆, M = Bi³⁺, Si⁴⁺, Mn⁴⁺, Ti⁴⁺, and (Bi^V_0.5Fe^III_0.5)⁴⁺) by employing a phase-switched oriented attachment method in the presence of [CrO₂]⁻. [CrO₂]⁻ and its hydrolyzed counterpart, CrOOH, are demonstrated to have a strong electrostatic interaction with the Bi-layer of an α-Bi₂O₃-phased precursor, inducing the formation of Cr-species coated α-Bi₂O₃ nanosheets. The subsequent phase transition from α-Bi₂O₃ to sillenite is found to weaken the interaction and release the Cr species, resulting in the formation of uncoated sillenite nanosheets. The nanosheets are ca. 1.5 nm thick and exhibit broad solar spectrum absorption above 600 nm. The photocatalytic activity on γ-Bi₂O₃ sillenite nanosheets is investigated by degrading ciprofloxacin pollutants. Remarkably, we observe a 16 times enhancement in photocatalytic performance compared to the particles and a 4.6-fold improvement over the well-known P25-TiO₂ catalyst. This enhancement is attributed to the sillenite nanosheet structure facilitating photogenerated charge separation and, consequently, boosting photocatalytic activity. In addition, it was found that γ-Bi₂O₃ nanosheets exhibited photocatalytic oxygen evolution performance, while γ-Bi₂O₃ nanoparticles did not exhibit oxygen evolution activity. Our discovery of these wide-spectrum-absorption sillenite nanosheets presents a promising avenue for the development of highly efficient photocatalysts, poised to harness sunlight for various applications in the future.