Hydrothermal Synthesis, Characterization And Properties Of Composite Electrode Based On The Keggin-type Fe/Mn-substituted Polyoxometallates

Polyoxometallates(POM), including heteropolyacid and heteropolyacid salt. Which are formed by simple oxysalt combine and dehydrate in a certain pH condition, POMs are as isoplyacid by only one oxysalt combine and dehydration, and POMs are as heteropolyacid by two oxysalts or more oxysalts combine and dehydration. The most traditional structures of POMs are Keggin-type, Anderson-type, Dawson-type, Silverton-type, Waugh-type and Lindquist-type such as H3PW12O40 and H6P2MO18O62. Polyoxometallates have an inch structure and theirs molecular excellent properties including polarity, oxidation reduction potential(ORP), surface charge distribution, morphology and acid, whose properties lead polyoxometallates have a wide application prospect in many areas, especially materials,catalysis, medicine etc.The paper use the traditional Keggin-type polyoxometallates are as basic unit, bringing in transition mental ions, to get a new series of polyoxometallate compounds by coordinate-cvatent bond, these compounds and their derivatives have a high catalytic activity.(1) A composite electrode of Cs4PW11O39Fe(III)(H2O)/C[CsPW11Fe/C] is fabricated with the hydrothermal method by using CsPW11 Fe as a precursor growing on the surface of a graphite electrode. After the composite electrode CsPW11Fe/C is characterized by infrared spectroscopy(IR), scanning electron microscope(SEM), transmission electron microscope(TEM) and X-ray diffraction(XRD) and the cycle voltammetry(CV). Its electrochemical properties and electrocatalytic activity towards H2O2 reduction are using the cycle voltammetry(CV) and alternating current impedance(EIS). The experimental results show that CsPW11 Fe has grown on the surface of the graphite electrode in the shape of cube. The size of CsPW11 Fe is 500 nm~1um. The study of CV and EIS imply that CsPW11Fe/C has an electrocatalytic activity towards H2O2, it is an excellent electrocatalyst.(2) A composite electrode of(NBu4)4PW11O39Fe(III)(H2O)/C [NBu4PW11Fe/C] is prepared by the hydrothermal method with NBu4PW11 Fe as a crystal precursor and a graphite electrode as substrate. And NBu4PW11Fe/C is characterized by IR, SEM, XRD, TEM and CV.And the electrochemical and electrocatalytic properties of the composite electrode are studiedusing electrochemical methods. The experimental results show that the NBu4PW11 Fe crystals grow on the surface of the graphite electrode in the size of micro-nanometer and keep diversiform geometrical shapes of dodecahedron. The crystalline layer is stable. The composite electrode has a remarkable electrocatalytic activity towards H2O2 reduction.(3) Cs5PW11O39Mn(II)(H2O)/C [CsPW11Mn/C] nanocrystal composite electrode is prepared by the hydrothermal method with Cs5PW11O39Mn(II)(H2O) [CsPW11Mn] powder as reactant and C12H25NaO3 S as surfactant. The composite electrode is characterized in details by IR, RS, UV-Vis, DRS, XRD, SEM, TEM and CV. The experimental results show that the growth of CsPW11 Mn nanocrystal on the surface of the graphite electrode is influenced by the reaction temperature, the reaction time and the surfactant amounts. The stable and complete CsPW11Mn/C nanocrystal composite electrode could be obtained for reaction time 30 hrs at hydrothermal temperature 180℃ and the mass ratio of surfactant and CsPW11 Mn 1:10.(4) Cs5PW11O39Mn(II)(H2O)/FTO[CsPW11Mn/FTO] is prepared by hydrothermal preparation method, which is that Cs5PW11O39Mn(II)(H2O) [CsPW11Mn] is loaded on the surface of FTO(the Fluorine mixed Tin oxide), and CsPW11Mn/FTO is characterized by IR,UV-Vis DR, SEM, CV. Influence factors of the crystal growth on the FTO surface are studied by a series of experiments such as different reaction time, the amount of C12H25NaO3 S,different acidity. The results show CsPW11 Mn could grow on the FTO surface at temperature180℃ for 30 hrs. At the same time, we study the photoelectric conversion properties of the solar battery. The experiments indicate that the CsPW11Mn/FTO has an excellent photoelectric performance.