Liangpeng Wu

Nano-CdS confined within titanate nanotubes for efficient photocatalytic hydrogen production under visible light illumination

CdS nanoparticles were confined within titanate nanotubes (TNTs) by an ion-exchange reaction and a subsequent sulfurization process. Prior to the ion-exchange reaction, the exterior surfaces of the TNTs were modified by a silane coupling agent to make CdS nanoparticles selectively deposit on the inner wall. The composites were characterized by high-resolution transmission electron microscopy, powder x-ray diffraction, inductively coupled plasma atomic emission spectrometry, N2 adsorption–desorption and UV–vis absorption spectra. The results confirm that CdS in the range of 2–3 nm in diameter are confined within the inner cavity of the TNTs. CdS confined within TNTs shows a significant blue-shift of the absorption band edge compared with CdS nanoparticles deposited on the exterior surface of TNTs. Also the TNTs-confined CdS composite exhibits enhanced photocatalytic activity and photostability for hydrogen evolution under visible light illumination due to the quantum size effect of CdS as a result of the spatial confinement effect of the TNTs.

Effect of MWCNT Inclusion in TiO2 Nanowire Array Film on the Photoelectrochemical Performance

Rutile TiO2 nanowire array films with multi-walled carbon nanotube (MWCNT) inclusion perpendicularly grown on fluorine-doped tin oxide (FTO) substrate were prepared by a facile hydrothermal method. The absorption edges of the TiO2 nanowire array films are blue-shifted with increasing MWCNT content. The resistance of the TiO2 nanowire array film is decreased by MWCNT inclusion. The optimum TiO2/MWCNT molar ratio in the feedstock is 1:0.1. For the TiO2 nanowire array film with MWCNT inclusion served as electrode in dye-sensitized solar cell (DSSC), an overall 194% increase of photoelectric conversion efficiency has been achieved.

Hierarchical flower-like titanium phosphate derived from H-titanate nanotubes for photocatalysis

Nanosheet-assembled hierarchical flower-like titanium phosphate (TiP) is synthesized via hydrothermal treatment of H-titanate nanotubes (Ti-NT) at the optimized conditions of 0.1xa0M of H3PO4 and hydrothermal temperature of 130xa0°C. A possible formation mechanism for the TiP flowers, involving the disintegration of Ti-NT and the growth and assembling of TiP nanosheets, is proposed. The main compositions of the uncalcined TiP flowers are titanium hydrogen phosphate hydrates (Ti(HPO4)2·xH2O), which can be transformed to titanium phosphate (TiP2O7) after high temperature calcination. The photocatalytic activity of the prepared TiP flowers is increased with the increased calcination temperature, which may be attributed to the better photocatalytic activity of TiP2O7 than Ti(HPO4)2·xH2O and the increased crystallization of TiP2O7.

Fabrication of TiO2 nanotubes-assembled hierarchical microspheres with enhanced photocatalytic degradation activity

TiO2 nanotubes-assembled hierarchical microspheres were fabricated by a one step hydrothermal route using P25 in NaOH aqueous solution with the assistance of H2O2, followed by temperature-programmed calcinations treatment at 400 °C. The photocatalytic activity of the sample was investigated by degradation of methyl orange under UV-light irradiation. The results show that TiO2 nanotubes-assembled hierarchical microspheres exhibit much higher photocatalytic degradation activity compared with that of TiO2 nanotubes, which could be attributed to its larger surface area, greater light reflection and the good light multiple scattering property.

Preparation of Titanate/N-Doped Anatase Composite Hierarchical Microspheres with Enhanced Visible Light Photocatalytic Activity

Titanate/N-doped anatase composite hierarchical microspheres have been obtained by calcination treatment of NH4-titanate hierarchical microspheres at proper temperatures. The phase structure is dependent on the calcination temperature and varies from titanate to anatase with increasing calcination temperature, with the heterophase in-between. The composite structure is verified by the results of XRD, visible and UV Raman spectra. The titanate/N-doped anatase composite sample calcined at 300xa0°C for 1xa0h exhibits enhanced activity in the degradation of Rhodamine B under visible light irradiation compared to the other samples. The enhanced activity can be ascribed to the synergistic effect of titanate and N-doped anatase.Graphical Abstract

TiO2 nanotube/ZnO nanorod/CdS on Ti mesh with three-dimensional array structure for photocatalytic degradation under visible light irradiation

The three-dimensional (3D) TiO2 nanotube arrays (TNTA) were prepared by electrochemical anodization of Ti mesh in a mixed electrolyte solution of (NH4)2SO4 and NH4F. Well-defined CdS-sensitized ZnO nanorod arrays (ZNRA/CdS) were successfully built on TNTA by the hydrothermal method and chemical bath deposition. The as-prepared samples were characterized by means of XRD, FESEM, and UV–Vis. The photocatalytic activities of the samples were evaluated by measuring the photodegradation of methylene blue (MB) in aqueous solution under visible light irradiation. The photocatalytic efficiencies for MB degradation were 49 and 60xa0% for Ti mesh/ZNRA/CdS and Ti mesh/TNTA/ZNRA/CdS after irradiation for 6xa0h, respectively. This can be attributed to the presence of TNTA at the bottom of a ZNRA/CdS composite, which provides a direct pathway for photoinjected electrons transferring along the photoanode to enhance charge-collection efficiency and consequently reduce electron–hole recombination. Furthermore, it can enlarge the practical applications range of TiO2 due to its 3D nanoarray structure with good light-harvesting ability and flexibility.