Synthesis of high-purity, layered structured K2Ta4O11 intermediate phase nanocrystals for photocatalytic water splitting

Abstract

High-purity K₂Ta₄O₁₁ (kalitantite) intermediate phase with a layered structure, as a new family member of alkali-metal tantalate semiconductors, was successfully prepared via a simple and cost-effective flux growth technique using potassium chloride (KCl) at a low temperature of 800 °C for only 4 h. The as-synthesized K₂Ta₄O₁₁ was characterized by XRD, SEM, TEM, STEM/EDS, and UV-Vis DRS, etc. It was found that the K₂Ta₄O₁₁ single nanocrystals were non-stoichiometric in the size range of 100–500 nm, and the indirect band gap of K₂Ta₄O₁₁ was correctly determined to be 4.15 eV. The K₂Ta₄O₁₁ not only exhibited a high and stable photocatalytic H₂ generation rate of ∼45.3 μmol h⁻¹ g⁻¹ in an aqueous methanolic solution with the photodeposition of Pt as co-catalysts, but also possessed the photocatalytic ability for simultaneous evolution of H₂ and O₂ in a stoichiometric ratio, with loading of NiO particles as cocatalysts. Thus, it can be mainly attributed to the benefits of KCl flux lowing the reaction temperature, and increasing the surface area and crystallinity of K₂Ta₄O₁₁, that the charge efficiency and enhancement of the photoreactivity for water splitting are improved.