Complex-Mediated Synthesis of Tantalum Oxyfluoride Hierarchical Nanostructures for Highly Efficient Photocatalytic Hydrogen Evolution

In this work, we have, for the first time, developed a facile wet-chemical route to obtain a novel photocatalytic material of tantalum oxyfluoride hierarchical nanostructures composed of amorphous cores and single crystalline TaO₂F nanorod shells (ACHNs) by regulating the one-step hydrothermal process of TaF₅ in a mixed solution of isopropanol (i-PrOH) and H₂O. In this approach, elaborately controlling the reaction temperature and volume ratio of i-PrOH and H₂O enabled TaF₅ to transform into intermediate coordination complex ions of [TaOF₃·2F]^2– and [TaF₇]^2–, which subsequently produced tantalum oxyfluoride ACHNs via a secondary nucleation and growth due to a stepwise change in hydrolysis rates of the two complex ions. Because of the unique chemical composition, crystal structure and micromorphology, the as-prepared tantalum oxyfluoride ACHNs show a more negative flat band potential, an accelerated charge transfer, and a remarkable surface area of 152.4 m² g^–1 contributing to increased surface reaction sites. As a result, they exhibit a photocatalytic activity for hydrogen production up to 1.95 mmol h^–1 g^–1 under the illumination of a simulated solar light without any assistance of co-catalysts, indicating that the as-prepared tantalum oxyfluoride ACHNs are a novel promising photocatalytic material for hydrogen production