2D/2D heterojunctions of WO3 nanosheet/K+Ca2Nb3O10− ultrathin nanosheet with improved charge separation efficiency for significantly boosting photocatalysis

Abstract

Harvesting solar energy using semiconductor photocatalysts for wastewater decontamination offers a greener solution to address serious environmental crises. Delamination of layer photocatalysts into ultrathin two-dimensional (2D) nanosheets has induced fascinating properties such as electronic/protonic-conductivity and photocatalytic and fluorescent properties. K⁺Ca₂Nb₃O₁₀⁻ is one prominent type of such materials, which is derived from the Dion–Jacobsen phase KCa₂Nb₃O₁₀ by exfoliation. Here, a Z-scheme WO₃/K⁺Ca₂Nb₃O₁₀⁻ binary 2D–2D heterojunction photocatalyst is successfully constructed through an easy hydrothermal coassembly method at room temperature. The as-synthesized WO₃/K⁺Ca₂Nb₃O₁₀⁻ photocatalyst exhibited remarkable improvement in the photodegradation performance of tetracycline hydrochloride under simulated sunlight irradiation as compared to pristine WO₃ and K⁺Ca₂Nb₃O₁₀⁻ nanosheets. Sample 20%-WO₃/K⁺Ca₂Nb₃O₁₀⁻ exhibited optimum efficiency, which is about 5.1-fold and 2-fold higher than those of WO₃ and K⁺Ca₂Nb₃O₁₀⁻, respectively. Such an improvement is mainly related to its strongly coupled heterointerfaces, enlarged specific surface area and improved charge carrier separation and transfer. Radical capturing experiments and the spin-trapping ESR technique demonstrate that both ˙O₂⁻ and h⁺ are the important active species responsible for the tetracycline hydrochloride degradation process over the nanosheet heterojunctions.