Efficient p-n Heterojunction Photocatalyst Composed of Bismuth Oxyiodide and Layered Titanate

Bismuth oxyhalides and layered alkali titanates are promising components to design high-performance hybrid photocatalysts. In this work, a hybrid photocatalyst composed of lepidocrocite-type layered cesium titanate (Cs_0.7Ti_1.77Li_0.23O₄, CsTLO) and bismuth oxyiodide (BiOI) was designed rationally based on lattice matching. BiOI formed on the layered titanate by ion exchange of CsTLO with Bi cations and subsequent growth of BiOI nanodisks (6 nm in the thickness and 125 nm in the lateral size) in an aqueous solution of cesium iodide, resulting in the hybrid where BiOI nanodisks were lying flat on the layered titanate and exposed the (001) facet predominantly. The present hybrid exhibited efficient photodegradation of methylene blue (4, 10, and 14 times higher than that of CsTLO, Bi-TLO, and BiOI, respectively), which was ascribed to the efficient charge transfer in the bulk and at the interface assisted by the built-in internal electric fields and the high activity of (001) BiOI for direct oxidation of the pollutant.