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The complete degradation of tetracycline still is a challenge for TiO2-based photocatalysts under simulated solar light irradiation. To tackle this challenge, we devise Ag nanoparticles (Ag NPs) confined in shell-in-shell hollow TiO2 photocatalyst (HTAT). This strategy mainly involves the construction of CPS@TiO2 core-shell composites, the form of TiO2 inner shell, AgNPs loading by photo-deposition, the assembly of TiO2 outer shell, and phase transition of anatase TiO2 by calcination at 450℃. All characterizations including TEM, STEM Mapping, BET, and XPS confirm the unique structure of the as-synthesized HTAT photocatalyst. As expected, the complete degradation of tetracycline (TC and TCH) can be realized by using HTAT photocatalyst under simulated solar light irradiation because its TiO2 two shells simultaneously take part in the photodegrading reaction of TC or TCH. The transformation intermediates and degradation pathway were analyzed by LC/MS. Our work effectively overcomes the disadvantages of many previously reported TiO2-based photocatalysts for the incomplete degradation of tetracycline.

TiO has been widely investigated as an electrode material because of its long cycle life and good durability, but the relatively low theoretical capacity restricts its practical application. Herein, we design and synthesize novel hierarchical SiO@C/TiO (HSCT) hollow spheres via a template-directed method. These unique HSCT hollow spheres combine advantages from both TiO such as cycle stability and SiO with a high accessible area and ionic transport. In particular, the existence of a C layer is able to enhance the electrical conductivity. The SiO layer with a porous structure can increase the ion diffusion channels and accelerate the ion transfer from the outer to the inner layers. The electrochemical measurements demonstrate that the HSCT-hollow-sphere-based electrode manifests a high specific capacitance of 1018 F g at 1 A g which is higher than those for hollow TiO (113 F g) and SiO/TiO (252 F g) electrodes, and substantially higher than those of all the previously reported TiO-based electrodes.

TiO2 has been widely used as a photocatalyst and an electrode material toward the photodegradation of organic pollutants and electrochemical applications, respectively. However, the properties of TiO2 are not enough up to meet practical needs because of its intrinsic disadvantages such as a wide bandgap and low conductivity. Incorporation of carbon into the TiO2 lattice is a promising tool to overcome these limitations because carbon has metal-like conductivity, high separation efficiency of photogenerated electron/hole pairs, and strong visible-light absorption. This review would describe and discuss a variety of strategies to develop carbon-doped TiO2 with enhanced photoelectrochemical performances in environmental, energy, and catalytic fields. Emphasis is given to highlight current techniques and recent progress in C-doped TiO2-based materials. Meanwhile, how to tackle the challenges we are currently facing is also discussed. This understanding will allow the process to continue to evolve and provide facile and feasible techniques for the design and development of carbon-doped TiO2 materials.

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