Enhanced photocatalytic activity of nonstoichiometric crystalline TaO2F and Ta2O5 with carbon coating

Pure and carbon-coated tantalum-based oxides photocatalysts were synthesized via the mesocrystalline precursor transformation method by annealing pure and polydopamine-coated (NH4)2Ta2O3F6 mesocrystals in Ar. The oxygen-poor atmosphere thermal annealing process assisted the formation of nonstoichiometric TaO2F mesocrystals with more F and Ta2O5 nanorods with oxygen vacancies and the associated lower valence state Ta ions (Ta4+). Furthermore, the carbon coating, decomposed from coated polydopamine, helped to control their particle size within 100 nm by isolating the connection of (NH4)2Ta2O3F6 subunits. Hence, as-synthesized products, particularly carbon-coated Ta2O5 nanosheets, owning large surface area (67.6 m2 g-1), fine particle size (<100 nm), excellent electronic conductivity, decreased bandgap energy, enhanced and extended absorption in the visible range, exhibited preferable photocatalytic activity in the photodegradation of methylene blue, reaching a 76.54 % and 41.71 % removal under ultraviolet and visible light illumination, suggesting a promising candidate for wide-range responsive photocatalytic applications.