Fahe Cao

Synthesis and electrochemical properties of substituted heteropoly acid with Dawson structure H-7[In(H2O)P2W17O61]center dot 23H(2)O

A new solid high-proton conductor, substituted heteropoly acid with Dawson structure H(7)[In(H(2)O)P(2)W(17)O(61)]·23H(2)O, has been synthesized by the degradation/ion exchange/freezing method. The pH of the synthesis reaction was given. The product was characterized by chemical analysis, IR, UV, XRD and TG-DTA. The determination of conductivity shows that H(7)[In(H(2)O)P(2)W(17)O(61)]·23H(2)O is an excellent solid high-proton conductor with conductivity of 1.34 × 10(-3) S cm(-1) at 18 °C, and 70% relative humidity (RH). Its activation energy is 37.72 kJ mol(-1), which suggests that its mechanism of proton conduction is the 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.