Peculiar reactions between interstitial compounds of transition metals and hydrogen peroxide and characterization of resultant materials

研究发现碳化钨与过氧化氢反应形成的过氧化物-草酸盐-多钨酸钨团簇具有较高的质子导电性。在本财政年度，我们研究了一种方法，将这种簇结合到有机基质中，以提高化学稳定性，并评估了由此获得的作为质子导电固体电解质膜的纳米杂化材料。将一水三氧化钨与双氧水在40℃下反应24 h，得到过氧化物钨酸配合物的均匀溶液。在溶液中加入草酸、丙二酸或二甲基丙二酸等羧酸，其与钨原子的比例为0.25-4.0，得到络合物。将该溶液加入到醇烷基化聚环氧乙烷-600的甲醇溶液中，在60℃下采用溶胶-凝胶法进行聚合。形成均匀透明的膜。在饱和水蒸汽压下，用交流阻抗法测定了这些膜在25 ~ 160℃温度范围内的质子电导率。典型膜在80℃时的电导率为1.4 × 10^<-2> sc -1，是单纯将PEO与二水合三氧化钨作为无机高质子导体混合制备的复合膜的10倍。这意味着钨酸盐团簇以纳米级均匀性分散在peo -基质中，形成了快速质子传输的渗透路径。振动谱和x射线衍射也证实了这种情况。虽然电导率在100℃以上随温度升高而下降，但在140 ~ 160℃范围内保持在10^<-4> Scm^<-1>的水平。体积大的配体如二甲基丙二酸盐倾向于抑制高温下的电导率下降。

It has been found that some tungsten oxide clusters like peroxo-oxalato-polytungstate formed by a reaction of tungsten carbide with hydrogen peroxide show high proton conductivity. In this fiscal year have studied a methodology to incorporate such a cluster into an organic matrix to enhance chemical stability, and evaluated nanohybrid materials thus obtained as a proton conductive solid electrolyte membrane.We obtained a homogeneous solution of a peroxotungstate complex by reacting tungsten trioxide monohydrate with hydrogen peroxide at 40℃ for 24 h. A carboxylic acid such as oxalic, malonic or dimethylmalonic acid was added to the solution at the ratio of 0.25-4.0 to tungsten atom, to yield a chelated complex. This solution was added to a methanol solution of alchoxysillilated poly (ethyleneoxide)-600 and polymerized at 60℃ by a sol-gel process. A homogeneous and transparent membrane was formed.Proton conductivity of those membranes was measured in the temperature range of 25-160℃ under suturated water vapor pressure by the ac impedance method. Conductivity of a typical membrane at 80℃ was 1.4x10^<-2> Scm-1, which was 10 times higher that that of a composite membrane fabricated by simply blending PEO and tungsten trioxide dihydrate as an inorganic high proton conductor. This means that tungstate clusters dispersed at a nano-level homogeneity throughout the PEO-matrix form a percolation path for fast proton transport. Such a situation was also confirmed by vibration spectra and X-ray diffraction. Although conductivity fell with raising temperature above 100℃, it remained at a level of 10^<-4> Scm^<-1> in the range of 140-160℃. Bulky ligands such as dimethylmalonate tended to suppress conductivity fall at high temperature.