Structural evolution from TiO2 nanoparticles to nanosheets and their photocatalytic performance in hydrogen generation and environmental pollution removal

Abstract

The rapid depletion of the fossil fuel reserves, and the increase of green-house gas emissions and other environmental pollutants, bring up an urgent need for the development of clean energy and sustainable environmental solutions. The ability to use sunlight to produce fuels such as H₂ from abundant, non-toxic resources, and to decompose environmental pollutants with benign photocatalysts, would revolutionize our civilization. TiO₂ has attracted substantial interest due to its activity for generating hydrogen from water under ultraviolet (UV) light irradiation. The discovery of (001) facet control with the fluoride additive in the reactants has triggered intensive studies for model photocatalysis. Here, we found that small TiO₂ nanoparticles were formed at the very beginning stage of the reaction, then were transformed into large TiOF₂ crystals, and finally turned into (001)-faceted TiO₂ nanosheets. TiOF₂ acted as a metastable intermediate medium in the transformation from TiO₂ nanoparticles into (001)-faceted TiO₂ nanosheets. The (001) face showed higher activity for the photocatalytic generation of hydrogen and the photodecomposition of methylene blue and rhodamine B. The synergic effect between TiOF₂ and TiO₂ nanosheets or nanoparticles further improved the photocatalytic activities. This study provides us with a promising solution for solving the energy and environment problems.