Abstract
Three-dimensional (3D) TiO2 hierarchical structures with various microstructures have been successfully synthesized via a surfactant-free and single-step solvothermal route, in which hydrochloric acid (HCl), nitric acid (HNO3), and acetic acid (HAc) are employed as the acid medium, respectively. The effects of acid medium on the microstructures and properties of 3D TiO2 hierarchical structure have been studied. The results indicate that 3D dandelion-like microspheres assembled of radial rutile nanorods are obtained in the sample prepared with HCl. Both the fraction of rutile and the diameter of nanorod enhance with the increasing HCl concentration. For the products derived from either HNO3 or HAc, 3D spheres composed of anatase nanoparticles are present. The 3D dandelion-like TiO2 hierarchical structures show low reflectance and efficient light harvesting since this ordered rod geometry offers a light-transfer path for incident light as well as multiple reflective and scattering effects. Moreover, 3D TiO2 with this unique topology shows superior photocatalytic activity despite low surface area, which can be ascribed to the enhanced light harvesting, fast electron transport, and low electron/hole recombination loss.
Highlights
Titania (TiO2) is widely used in various applications such as photocatalysis of pollutants, catalyst for selective catalytic reduction, photosplitting of water, transparent conducting electrode for dye-sensitized solar cells, electrolyte for proton exchange membrane fuel cells, etc. because of its nontoxicity, low-cost, and chemical stability [1,2,3,4,5,6,7,8,9]
Our subsequent study revealed that the acid medium is essential to the microstructures, optical absorption, diffuse reflectance properties and, photocatalytic activities of the synthesized 3D TiO2 structures
The results reveal that the precursor containing hydrochloric acid (HCl) as the acid medium has a tendency to form rod-shaped rutile titania, whereas anatase particles are obtained when either HNO3 or HAc is used
Summary
Titania (TiO2) is widely used in various applications such as photocatalysis of pollutants, catalyst for selective catalytic reduction, photosplitting of water, transparent conducting electrode for dye-sensitized solar cells, electrolyte for proton exchange membrane fuel cells, etc. because of its nontoxicity, low-cost, and chemical stability [1,2,3,4,5,6,7,8,9]. Synthesis of 3D ordered TiO2 assemblies of nanoparticles, nanorods, nanowires, and nanotubes have been reported [23,24,25,26], for instance, interesting dandelion-like structures [23,26], but the performance and properties are rarely investigated. Our subsequent study revealed that the acid medium is essential to the microstructures, optical absorption, diffuse reflectance properties and, photocatalytic activities of the synthesized 3D TiO2 structures. The effects of acid medium on the microstructures and properties of 3D TiO2 hierarchical structures have not been reported. 3D TiO2 hierarchical structures with distinct microstructures have been synthesized in various acid media via a surfactant-free and single-step solvothermal route. The optical absorption and diffuse reflectance as well as photocatalytic performance of 3D TiO2 hierarchical structures were investigated
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