This paper reports first on the novel synthesis of hierarchical tin dioxide (SnO2) porous microspheres in the absence of a template using a simple spray reaction technique and annealing at 500–800 °C. The SnO2 microspheres obtained are tetragonal phase and approximately 2.2–2.7 μm in diameter, and they consist of 6.7–23.1 nm crystallites and possess hierarchical pores and Brunauer–Emmett–Teller (BET) surface areas of up to 55 m2 g−1. Using ultraviolet-visible absorption spectra analysis, it is found that SnO2 crystallites demonstrate a quantum size effect, resulting in a widening of the band gap of the SnO2 spheres. This band gap can be tuned from 3.99 eV (800 °C) to 4.26 eV (600 °C) by varying the annealing temperature. Using separated SnO2 porous spheres as the scattering layer of the photoanode for dye sensitized solar cells (DSSCs), the solar light-electricity conversion efficiency (maximum: 6.0%) is increased by up to 31.9% and 28.2% compared to cells using a commercial SnO2 powder and P25 nanopowder as the scattering layers, respectively, under the same conditions.

Poor electrocatalytic activity and carbon monoxide (CO) poisoning of the anode in Pt-based catalysts are still two major challenges facing direct methanol fuel cells. Herein, we demonstrate a highly active and stable Pt nanoparticle/Mo2C nanotube catalyst for methanol electro-oxidation. Pt nanoparticles were deposited on Mo2C nanotubes using a controllable atomic layer deposition (ALD) technique. This catalyst showed much higher catalytic activity for methanol oxidation and superior CO tolerance, when compared with those of the conventional Pt/C and PtRu/C catalysts. The experimental evidence from X-ray absorption near-edge structure spectroscopy and scanning transmission X-ray microscopy clearly support a strong chemical interaction between the Pt nanoparticles and Mo2C nanotubes. Our studies show that the existence of Mo2C not only minimizes the required Pt usage but also significantly enhances CO tolerance and thus improves their durability. These results provide a promising strategy for the design of highly active next-generation catalysts.

Gibbs free energy was applied to analyze the carbothermal reduction process of TiO2. The phase stable diagram of Ti–C–CO was drawn, and it can be found that TiO2 will be reduced to Ti–O Magnéli phase, TinO2n–1 (3 < n < 10) or Ti3O5 first and then further reduced to TiC. However, in the present study, it was found that Ti4O7 can be reduced to TiC directly when the temperature was lower than 800 K and lg(pco/pθ) < −1.1. The reduction route was proved by the results of non-isothermal TG–DTA combined XRD. The isothermal analysis of carbothermal reduction process of TiO2 via TG–DTA under the temperature of 1363, 1413, 1463 and 1513 K was performed. The whole reduction process was divided into two sections: Initially it was rate controlled by an interfacial reaction, and later was rate controlled by three-dimensional diffusion. The modified mathematical expressions were deduced. They fit the experimental curves well. Their activation energy of steps was 241.1 and 323.4 kJ mol−1, respectively.

In this work, sub-stoichiometric tungsten oxide W18O49 was first studied as a support for a Pt catalyst. Metallic monoclinic W18O49 nanorods (NRs) with an isotropic morphology can not only improve electron, reactant, and product transport but can also enhance the utilisation of Pt for the methanol oxidation reaction (MOR). The specific activity for the forward peak (If) of Pt/W18O49 was determined to be 1.14 mA cmPt−2, which is approximately 1.4 and 1.8 times higher than that of Pt-black and Pt/C, respectively. On the other hand, the robust W18O49 NRs improve the stability of Pt/W18O49. After a 5000-cycle accelerated durability test, the electrochemical surface area (ECSA) loss rate of Pt/W18O49 was only 27.12%, less than that of Pt-black and Pt/C. Moreover, numerous oxygen vacancies and two valence states of W (W5+ and W6+) were found to co-exist in W18O49, which may promote hydrogen spillover and oxygen buffering. These effects together contributed to improve the anti-poisoning properties of Pt/W18O49 towards the intermediates in the MOR. The peak current ratio of the forward versus the backward (If/Ib) reaction is 1.12 for Pt/W18O49, 0.99 for Pt-black, and 0.79 for Pt/C. It was found that the Magnéli phase W18O49 may be a promising catalyst support for use in the MOR.

We report on the successful synthesis of fiber-like nanostructured Ti4O7 (NS-Ti4O7) by multistep method. The specific surface area of this NS-Ti4O7 was 26 m2 g−1. The synthesized NS-Ti4O7 was platinized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing. It was found that the monodispersed Pt nanoparticles supported on NS-Ti4O7 with a uniform size of 4.8 nm. The prepared Pt/NS-Ti4O7 catalysts exhibited superior durability as well as enhanced Pt mass activity in comparison to commercial Pt/XC-72 catalyst. After undergoing accelerated durability tests (ADT), the oxygen reduction reaction (ORR) mass activity of Pt/NS-Ti4O7 was nearly thirty times higher than that of Pt/XC-72. The superior durability of Pt/NS-Ti4O7 is attributed to the high stability of Ti4O7 and the strong metal–support interaction between Pt and Ti4O7.

In this work, sub-stoichiometric tungsten oxide W18O49 was first studied as a support for a Pt catalyst. Metallic monoclinic W18O49 nanorods (NRs) with an isotropic morphology can not only improve electron, reactant, and product transport but can also enhance the utilisation of Pt for the methanol oxidation reaction (MOR). The specific activity for the forward peak (If) of Pt/W18O49 was determined to be 1.14 mA cmPt−2, which is approximately 1.4 and 1.8 times higher than that of Pt-black and Pt/C, respectively. On the other hand, the robust W18O49 NRs improve the stability of Pt/W18O49. After a 5000-cycle accelerated durability test, the electrochemical surface area (ECSA) loss rate of Pt/W18O49 was only 27.12%, less than that of Pt-black and Pt/C. Moreover, numerous oxygen vacancies and two valence states of W (W5+ and W6+) were found to co-exist in W18O49, which may promote hydrogen spillover and oxygen buffering. These effects together contributed to improve the anti-poisoning properties of Pt/W18O49 towards the intermediates in the MOR. The peak current ratio of the forward versus the backward (If/Ib) reaction is 1.12 for Pt/W18O49, 0.99 for Pt-black, and 0.79 for Pt/C. It was found that the Magnéli phase W18O49 may be a promising catalyst support for use in the MOR.

We report on the successful synthesis of fiber-like nanostructured Ti4O7 (NS-Ti4O7) by multistep method. The specific surface area of this NS-Ti4O7 was 26 m2 g−1. The synthesized NS-Ti4O7 was platinized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing. It was found that the monodispersed Pt nanoparticles supported on NS-Ti4O7 with a uniform size of 4.8 nm. The prepared Pt/NS-Ti4O7 catalysts exhibited superior durability as well as enhanced Pt mass activity in comparison to commercial Pt/XC-72 catalyst. After undergoing accelerated durability tests (ADT), the oxygen reduction reaction (ORR) mass activity of Pt/NS-Ti4O7 was nearly thirty times higher than that of Pt/XC-72. The superior durability of Pt/NS-Ti4O7 is attributed to the high stability of Ti4O7 and the strong metal–support interaction between Pt and Ti4O7.