Hongxiao Zhao

First observation of visible light photocatalytic activity of carbon modified Nb2O5 nanostructures

Carbon-modified niobium oxide (Nb2O5) nanostructures, that firstly exhibited good visible light photocatalytic activity of Nb2O5 species, were synthesized by utilizing a low temperature, one-pot nonaqueous sol–gel approach. The resulting products were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption. Unlike the commercial or other reported Nb2O5 products that only respond to the UV-light irradiation, the present carbon-modified Nb2O5 nanostructures obtained at 200 °C in our experiment exhibited much better photocatalytic activity on degradation of RhB under visible light, which was about 39 times of that of commercial Nb2O5, 18 times of that of Degussa P25, and 5 times of that of carbon modified mesoporous TiO2. Moreover, these carbon-modified Nb2O5 nanostructures were also able to efficiently split water under visible light. The growth mechanism and the origin of visible light photocatalytic activity of the resulting Nb2O5 nanostructures were proposed. These carbon-modified Nb2O5 products are expected to be more suitable candidates than that of the most studied TiO2 as visible light photocatalysts.

Fabrication and application of MFe2O4 (M = Zn, Cu) nanoparticles as anodes for Li ion batteries

In this work, MFe2O4 (M = Zn, Cu) nanoparticles were successfully prepared by a hydrothermal method. The structure, morphology, microstructure, specific surface area and electrochemical properties of the resultant particles were characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physical adsorption, charge–discharge test and cyclic voltammetry (CV) method, respectively. The resulting ZnFe2O4 and CuFe2O4 products were sphere-like and cubic-shaped particles and their average size was about 30–40 nm and 60–70 nm, respectively. The initial discharge capacities of ZnFe2O4 and CuFe2O4 electrodes reached 1287.5 mAh g−1 and 1412.3 mAh g−1, respectively, at a current density of 0.2 mA cm−2 in a potential range of 0.0–3.0 V. This indicated that Cu is a better counter ion than Zn. The resulting MFe2O4 nanoparticles are expected to be a promising candidate of anode materials for Li ion batteries. The reaction mechanism of MFe2O4 nanoparticles in Li ion batteries was also discussed based on the CV of Li/MFe2O4 cell.

Substitute of Expensive Pt with Improved Electrocatalytic Performance and Higher Resistance to CO Poisoning for Methanol Oxidation: the Case of Synergistic Pt-Co3O4 Nanocomposite

In this paper, Pt-Co3O4 nanocomposite was synthesized by a sol-gel process combined with electrodeposition method. Its electrocatalytic activity towards methanol oxidation was investigated at room temperature using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and current density-time curve. It is found that the resultant Pt-Co3O4 catalysts with minute amount of Pt exhibite attractive electrocatalytic activity for methanol oxidation reaction (MOR) but with a high resistance CO poisoning due to the synergistic effects from Pt and Co3O4. Together with the low manufacturing cost of Co3O4, the reported nanostructured Pt-Co3O4 catalyst is expected to be a promising electrode material for direct methanol fuel cells (DMFC).

Design and synthesis of ternary semiconductor Cu7.2(SexS1−x)4 nanocrystallites for efficient visible light photocatalysis

A new series of ternary semiconductor compounds, Cu7.2(SexS1−x)4 (0.2 ≤ x ≤ 0.8) nanocrystallites, that exhibited good photocatalytic activity under visible-light irradiation, were facilely synthesized under mild conditions. The Cu7.2(SexS1−x)4 nanocrystallites were characterized by powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and UV-Vis absorption spectra. From X-ray data it is found that the cell constant a of different samples varies linearly with the composition x as: a (A) = 5.5959 + 0.1586x. UV-Vis absorption spectra indicate that the apparent band gap energies can be tuned by adjusting the composition x so as to better match to the whole solar spectrum. Unlike the most studied TiO2 that only responds to the UV-light irradiation, the present Cu7.2(SexS1−x)4 nanocrystallites exhibited much better photocatalytic activity under visible light on degradation of RhB. It is believed that the photocatalytic superiority of the Cu7.2(SexS1−x)4 nanocrystallites is mainly due to the compositional gradient arisen from uneven distribution of Se/S compositions in the compounds, which may induce a more efficient charge separation/transport in the Cu7.2(SexS1−x)4 photocatalysts.

Facile non-injection synthesis of high quality CZTS nanocrystals

We present a facile, non-injection synthesis of high quality CZTS nanocrystals by using simple inorganic salts, sulfur powders and (CH3)3COK (KTB) as precursors. The uniqueness and creativity is the utilization of KTB as sulfur activating agent and stabilizing surfactant agent.

Construction of cross-linked polymer films covalently attached on silicon substrate via a self-assembled monolayer

A new synthetic approach was developed to fabricate cross-linked polymer films covalently attached on a silicon substrate via a self-assembled monolayer (SAM) using a low energy proton beam as the initiator. The widely used silane coupling reagent 3-(mercaptopropyl) trimethoxysilane [HS(CH2)3Si(OCH3)3] was employed as an intermediate SAM to chemically bond the cross-linked polymer film to the silicon substrate. Dotriacontane was selected as a precursor that was spin-coated on the SAM-terminated silicon wafers. The film thickness can be easily controlled by spin-coating precursor solutions of different concentrations. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements confirmed the formation of SAM on the silicon substrate and the subsequent cross-linkage between the SAM and the upper polymer film formed. The resulting cross-linked polymer films are relatively stable, with all layers covalently attached together so that the whole film could not be removed by rinsing in both organic solvent and even more reactive HF solutions. In particular, the resistance of the cross-linked polymer film towards HF etching can be useful for lithography and device fabrication for polymer based electronics. The capability of using different SAMs to attach various polymer films was also demonstrated.

An Au buffer layer for the growth of a ZnO sol–gel film on a Si substrate

In this work, we demonstrate the influence of an Au buffer layer on the structure and photoluminescence (PL) properties of ZnO sol–gel thin films on Si substrates. An Au layer was deposited on the silicon substrate by the evaporation deposition method from highly pure Au (99.99%) wires. Then, a ZnO film was prepared by the sol–gel method with spin-coating technology, followed by calcinations in air at 600 °C for 1 h. The structures and morphologies of the prepared films were characterized by x-ray diffraction, energy dispersive spectrum analysis, atomic force microscopy and PL. The results show that the prepared ZnO thin film with an Au buffer layer exhibits good crystallinity and surface morphology compared with that without an Au buffer layer. Interestingly, different from other previous reports on buffer layers with PL-enhanced properties, the ZnO thin film with Au buffer layer showed an obvious violet PL-quenched property.

Thermal physical properties of Al-coated diamond/Cu composites

To acquire a well bonded interface between the copper and the diamond particles in diamond-copper matrix composites, an available process to apply a vapor deposited aluminum (Al) coating onto diamond particles was used to solve this interfacial problem. The diamond-copper matrix composites were prepared by spark plasma sintering (SPS) process and the effect of Al-coated diamond particles was demonstrated. The experimental results showed that the densification, interfacial bonding and thermal conductivity of Al-coated composites were evidently improved compared to those of the uncoated composites. A maximum thermal conductivity (TC) of 565 W/(m·K) was obtained in the coated composite containing 50vol% diamond particles sintered at 1 163 K. Additionally, the experimental data of thermal conductivity and coefficient of thermal expansion (CTE) were compared with the predictions from several theoretical models.

The synthesis and electrochemical performance of Cu6Sn5 intermetallic nanoparticles as anode material in Li ion batteries

Abstract Cu6Sn5 intermetallic nanoparticles have been successfully prepared by a simple reduction method. The crystallinity and morphology of the synthesized products were characterized by means of X-ray diffraction and scanning electron microscopy, respectively. When used as anode material, Cu6Sn5 intermetallic nanoparticles demonstrated an initial discharge capacity of 3368.2 mAh · g−1 and stable capacities of 840 mAh · g−1 after 70 cycles between 0.05 and 2.5 V at a current density of 100 mA · g−1. The charge–discharge process of Cu6Sn5 intermetallic nanoparticles was also evaluated using cyclic voltammetry. The results indicated Cu6Sn5 intermetallic nanoparticles may be an ideal anode material for Li ion batteries.