Carbon nitride (CN) polymers sensitized with N-doped tantalic acid were prepared by pyrogenation of the mixture of urea and tantalic acid at 400 °C. X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectrometry (EDS), and Fourier transform infrared spectroscopy (FTIR) results indicated that the CN polymers were successfully modified on the surface of the N-doped tantalic acid. UV−vis diffusion reflectance spectra (DRS) showed that the absorption edge of the CN polymers sensitized with N-doped tantalic acid red-shifted remarkably to the visible light region compared with bare tantalic acid. This new kind of CN polymers sensitized with N-doped tantalic acid showed a high photocatalytic activity and good stability for hydrogen evolution from an aqueous methanol solution under visible light (λ ≥ 410 nm) irradiation, and up to 4.8% of the apparent quantum yield was achieved at 420 nm. The protonic acidity of the tantalic acid makes themselves interact more intenser with the CN polymers, and easily hydrate in the aqueous solutions, so the separation probabilities of the photogenerated charge carriers would be improved.

Colorful rutile TiO2 was prepared by heating Ti2O3 at 550–900 °C to develop novel visible-light-sensitive and eco-friendly photocatalysts for environmental remediation under visible-light irradiation. The colors of the prepared samples, which ranged from grayish green to yellowish off-white via yellow differed from the reported colors of reduced TiO2, such as blue and black. The TiO2 prepared in this study was characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and UV–Visible spectroscopy. These measurements showed that the TiO2 contained Ti3+-interstitial sites. The TiO2 was sensitive to visible light, and calculation of the band diagram demonstrated that this visible-light absorption is caused mainly by formation of Ti3+-interstitial sites in rutile TiO2. Among the prepared samples, the TiO2 prepared by heating Ti2O3 at 700 °C shows the highest photocatalytic activity under visible-light irradiation. In addition, the sample was further and mildly ground using a bead-milling machine. The ground sample possessed higher surface area and better photocatalytic activity.

Sn2+-incorporated potassium titanate (K2Ti6O13) nanoribbons were prepared by a facile acid-free ion-exchanged method in a dehydrated methanol solution at room temperature. XRD patterns suggested that K2Ti6O13 (KTO) and Sn2+-incorporated KTO (SKTO) are well crystallized with monoclinic phase structures. The mole ratio of incorporated Sn2+ to K+ in SKTO was estimated to be 2. X-ray photoelectron spectrum showed that the Sn species of SKTO consisted of 90% of Sn2+ and 10% of Sn4+, suggesting that part of Sn2+ was oxidized to Sn4+ in the incorporation process. The band gap of SKTO was 0.7 eV narrower than that of KTO, which was derived from lift of the top of the valence band due to the hybridization of Sn5s and O2p orbitals. The SKTO nanoribbons showed remarkable photocatalytic activities for H2 evolution and rhodamine B degradation under visible light irradiation (λ ≥ 420 nm). The photocatalytic mechanism and durability were studied in detail. The advantage of this acid-free ion-exchange method is ease of ion-exchange of K+ with H+ and maintenance of the integrity of the 1D nanoribbon structures. This method can be applied to preparation of other Sn2+-incorporated compounds with special nanostructures.

Titanate network films were grown in situ on a Ti foil by a fast microwave-assisted hydrothermal method. The titanate network (STN) films were formed by twisting of long one dimensional (1D) multi-walled titanate nanotubes. Compared with the traditional hydrothermal method, the applied microwaves can accelerate the reaction rate and this method can save time. To expand the light absorption capability, PbS and CdS nanocrystals were uniformly sensitized on the STN film. After sensitization, the light absorption was remarkably shifted to the long wavelength direction, while the network structures of the film were kept. The PbS-STN and CdS-STN films showed enhanced photocatalytic activities for MO degradation compared to the bare STN film and N-TiO2 film. These enhanced photocatalytic activities were possibly due to the large BET surface areas of the titanate nanotubes, more light harvesting in the channels of the surface network structure, and the high separation probability of the photo-generated electron–hole pairs. Furthermore, it is interesting that all of the STN, PbS-STN, and CdS-STN films showed the super-amphiphilicity without any light irradiation, which may be due to the roughness of the surface network structures. And this super-amphiphilicity was kept even after exposure to air for more than 6 months.

WO3 modified titanate network film was prepared by an improved low-temperature two-step hydrothermal method. It showed a high mineralization yield (over 90%) for 2-propanol (IPA) photo-decomposition by only 2 h of visible light (λ ≥ 420 nm) irradiation. Furthermore, it exhibited quite good stability in this photocatalytic mineralization.

Prevention against H2S-derived catalyst deactivation on Pd catalyst (Pd/TiO2) was investigated using TiO2 photocatalytic reaction. The catalytic activity was evaluated by CO oxidation. In the dark, the catalytic activity reduced and completely deactivated in the presence of H2S. In contrast, under UV light illumination condition, even in the presence of H2S with the same concentration, it was found that the catalyst kept the activity because of the photocatalytic reaction of TiO2, resulting in the oxidation of H2S to sulfate. The completely deactivated catalyst was also regenerated by the photocatalytic reaction.

Titanate network films were grown in situ on a Ti foil by a fast microwave-assisted hydrothermal method. The titanate network (STN) films were formed by twisting of long one dimensional (1D) multi-walled titanate nanotubes. Compared with the traditional hydrothermal method, the applied microwaves can accelerate the reaction rate and this method can save time. To expand the light absorption capability, PbS and CdS nanocrystals were uniformly sensitized on the STN film. After sensitization, the light absorption was remarkably shifted to the long wavelength direction, while the network structures of the film were kept. The PbS-STN and CdS-STN films showed enhanced photocatalytic activities for MO degradation compared to the bare STN film and N-TiO2 film. These enhanced photocatalytic activities were possibly due to the large BET surface areas of the titanate nanotubes, more light harvesting in the channels of the surface network structure, and the high separation probability of the photo-generated electron–hole pairs. Furthermore, it is interesting that all of the STN, PbS-STN, and CdS-STN films showed the super-amphiphilicity without any light irradiation, which may be due to the roughness of the surface network structures. And this super-amphiphilicity was kept even after exposure to air for more than 6 months.

WO3 modified titanate network film was prepared by an improved low-temperature two-step hydrothermal method. It showed a high mineralization yield (over 90%) for 2-propanol (IPA) photo-decomposition by only 2 h of visible light (λ ≥ 420 nm) irradiation. Furthermore, it exhibited quite good stability in this photocatalytic mineralization.