Qingyin Wu

A facile one-step method to produce Ni/graphene nanocomposites and their application to the thermal decomposition of ammonium perchlorate

A facile one-step method was used to prepare Ni/graphene nanocomposites under solvothermal conditions. During this one-step process graphene oxide was reduced to graphene and Ni nanoparticles were simultaneously anchored on graphene sheets as spacers to keep the neighbouring sheets separated under the conditions generated in the solvothermal system. The size and content of the Ni nanoparticles distributed on the graphene sheets can be easily controlled by altering the starting concentration of NiCl2·6H2O. The catalytic performance of the as-synthesized Ni/graphene nanocomposites on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermal gravimetric and differential thermal analysis (DTA). The results show that Ni/graphene nanocomposites exhibit high catalytic activity. The peak temperature of the high-temperature decomposition of AP decreased by 97.3 °C and at the same time the peak of the low-temperature decomposition disappeared. When 1% Ni/graphene nanocomposites are used, the catalytic performance is the best. As a result, the Ni/graphene nanocomposites could be a promising candidate material for an AP-based propellant.

Thermoregulated polyoxometalate-based ionic-liquid gel electrolytes

A series of vanadium-substitutive polyoxometalate-based ionic liquids, [PyPS]6PW9V3O40, [PyPS]4PW11VO40, [PyPS]4PMo11VO40 and [PyPS]7P2W17VO62, bearing sulfo-group grafted ammonium (PyPS), are transformed to reversible thermal-response gel-type compounds. Interestingly, these gel-type compounds exhibit an obvious increase in their conductivity during the reversible phase transformation, which means that they are a novel series of reversible thermal-response gelation electrolytes. The relationship between the component elements of the polyoxometalate-based ionic liquids and their electrochemical performances has been studied. The Dawson-type compound ([PyPS]7P2W17VO62) has a higher conductivity than the Keggin-type one ([PyPS]4PW11VO40) with the same number of vanadium atoms in the structure. What’s more, the W-containing compounds ([PyPS]6PW9V3O40 and [PyPS]4PW11VO40) have higher conductivities than the Mo-containing one ([PyPS]4PMo11VO40).

Synthesis and conductive performance of indium-substituted ternary heteropoly acids with Keggin structures

Two new high-proton conductors, indium-substituted ternary heteropoly acids with Keggin structures, H4[In(H2O)PW11O39]·11H2O and H5[In(H2O)SiW11O39]·8H2O, have been synthesized and characterized using elemental analysis, IR, UV, XRD and TG-DTA. Their proton conductivities were measured using electrochemical impedance spectroscopy (EIS), and the results indicate that H4[In(H2O)PW11O39]·11H2O and H5[In(H2O)SiW11O39]·8H2O are solid high-proton conductors with a conductivity of 2.60 × 10(-4) S cm(-1) and 5.25 × 10(-4) S cm(-1), respectively, at 18 °C and 80% relative humidity (RH). Their activation energies are 33.40 kJ mol(-1) and 28.52 kJ mol(-1), which suggests that the mechanism of proton conduction is the vehicle mechanism. In the range of the measured temperatures, the conductivity of both heteropoly acids increases with higher temperatures.

Synthesis and conduction mechanism of high proton conductor H6SiW10V2O40⋅14H2O

A ternary heteropoly acid (HPA) H6SiW10V2O40⋅14H2O was prepared and investigated in this paper. The structure feature and hydration of this HPA was characterized by IR, XRD, UV, and TG-DTA. This HPA exhibits a high proton conductivity, which is 7.4×10−3S⋅cm−1 at 25∘C and 70% relative humidity. It is a novel high proton conductor. The conductivity increases with higher temperature, and it exhibits Arrhenius behavior, with the activation energy value of 21.02kJ⋅ mol−1 for proton conduction, indicating the proton conduction mechanism is dominated by vehicle mechanism.

Solid high-proton conductor tungstovanadozincic acid with transition metal as central atom: Synthesis and conductivity

A Keggin-type vanadium-substituted tungstovanadozincic heteropoly acid H7ZnW11VO40 ⋅ 8H2O, with the transition metal as central atom, was firstly synthesized and characterized. Its proton conductivity was measured by the electrochemical impedance spectrum (EIS), and the result indicates that the H7ZnW11VO40 ⋅ 8H2O is a solid high-proton conductor with conductivity of 3.26 × 10-3S ⋅ cm-1 at 58°C, 50% relative humidity. Its activation energy is 29.50 kJ ⋅ mol-1, which suggests that the mechanism of proton conduction is the Vehicle mechanism.

Syntheses and electrochemical properties of polyoxometalate salts with Dawson structure

Two new solid hybrid molecular materials [PyPS]H6P2W17VO62 and [PyPS]H8P2W15V3O62 have been synthesized from 1-(3-sulfonic group) propyl-pyridine ionic liquid cation and tungstovanadophosphoric anion with the Dawson structure. They were characterized by element analysis, impedance spectroscopy (IS), IR- and UV-spectroscopy. The formation of the hybrid molecular compounds with the Dawson structure was showed. Ion conductivity of [PyPS]H6P2W17VO62 and [PyPS]H8P2W15V3O62 are 3.99 × 10−3 and 7.37 × 10−3 S cm−1 at 18°C and 55% relative humidity respectively. The activation energies of proton conductivity are 28.2 and 26.7 kJ mol−1 respectively.

PREPARATION AND ELECTROCHEMICAL PERFORMANCE OF HYBRID MATERIALS CONTAINING HETEROPOLY ACID WITH DAWSON STRUCTURE AND POLYMERS

Highly proton-conducting hybrid materials (P2W17V/PEG and P2W17V/PEG/SiO2) were prepared by heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure (P2W17V, 90 wt.%), polyethylene glycol (PEG, 10 wt.% and 5 wt.%) and silica gel (SiO2, 0 wt.% and 5 wt.%). The products were characterized by the infrared (IR) spectrum, X-ray powder diffraction (XRD) analysis and electrochemical impedance spectrum (EIS). The result reveals that their conductivity values are 1.02 × 10-2 and 2.58 × 10-2S ⋅ cm-1 at room temperature (26°C) and 75% relative humidity (RH), respectively. Their conductivities increase with higher temperature and these activation energies of proton conduction are 9.51 and 14.95 kJ⋅mol-1, which are lower than that of pure heteropoly acid (32.23 kJ⋅mol-1). These mechanisms of proton conduction for these two materials are Grotthuss mechanism.

PW9V3/rGO/SPEEK hybrid material: an excellent proton conductor

To improve the proton conductive performance of heteropoly acids, sulfonated polyether ether ketone (SPEEK) and reduced graphene oxide (rGO) were introduced into a tungstovanadophosphoric acid (H6PW9V3O40, abbreviated as PW9V3) to prepare a hybrid film material. The results indicate that the Keggin framework of the PW9V3O406− anion still remains in the hybrid material and confirm the homogeneous dispersion of PW9V3 on the surface of graphene sheets, which results in a better stability of PW9V3. The obtained PW9V3/rGO/SPEEK hybrid material exhibits appreciable proton conductivity of 6.2 × 10−2 S cm−1 at 17 °C and 70% relative humidity because the introduction of rGO and SPEEK into PW9V3 can help to form more hydrogen bonds in the HPA-based material. The conductivity of the PW9V3/rGO/SPEEK hybrid material enhances with the increase of temperature, and it shows Arrhenius behavior with the activation energy value of 18.7 kJ mol−1, indicating that the proton conduction in this film occurs by a mixing mechanism. It is an alternative hybrid film material which may be applied in the field of proton exchange fuel cells.

Reversible phase transformation-type layer shape electrolyte based on POM and quaternary ammonium salt

A novel kind of organic–inorganic layer shape material, polyoxymetalates (POM)-type ionic liquid (IL) with Keggin structure and simple quaternary ammonium salt, (TOAMe)4PW11VO40 (trioctylmethylammonium = TOAMe,…) is synthesized and characterized by IR, UV, X-ray diffraction (XRD), TG–DTA. Its electrochemical property was investigated by cyclic voltammgram. Research results released the vanadium and the POM structure in the compound can process reduction in DMSO, which is unlikely in water solution as a simple hydrated ion because water will protonize substrate.

Synthesis and performance of solid proton conductor molybdovanadosilicic acid

A molybdovanadosilicic acid H5SiMo11VO40·8H2O was synthesized and investigated in this work. The structure features and hydration degree of this acid were characterized by IR, UV, XRD and TG-DTA. Its proton conductivity was studied by electrochemical impedance spectroscopy (EIS). The EIS measurements demonstrated that H5SiMo11VO40·8H2O showed excellent proton conduction performance with proton conductivity reaching 5.70 × 10−3 S cm−1 at 26 °C and 70% relative humidity. So, it is a new solid high proton conductor. The conductivity enhances with the increase of temperature, and it exhibits Arrhenius behavior. The activation energy value for proton conduction is 21.4 kJ mol−1, suggesting that the proton transfer in this solid acid is dominated by Vehicle mechanism.