Development of fuel cell and electrochemical devices using inorganic proton-conducting materials

溶胶-凝胶法被广泛应用于制备具有新成分的新功能玻璃。综述了近年来我们在制备高质子电导率玻璃及其在电子器件中的应用方面的研究进展。用水解法制备了含某些金属氧化物的P_2O_5-SiO_2系玻璃，加热至~600℃。得到的玻璃是多孔的，孔的直径小于几纳米，孔中含有水分子。玻璃中的电导与质子从羟键上解离以及质子在水分子中的跳跃有关。在溶胶-凝胶基质中，磷钼酸(PMA)和磷钨酸(PWA)被认为是最主要的掺杂剂。一种新型杂多酸玻璃材料在室温下可获得较高的质子电导率(10-2 S/厘米)。尽管如此，它们在30℃和30%相对湿度下仍表现出极具吸引力的燃料电池性能(~22.2 mW/cm2)和高稳定性。水合作用破坏了玻璃中的长链磷酸盐结构，质子破坏了链之间的交联键，导致与非桥氧连接。随后，水分子在质子周围形成氢键。该水凝胶在室温下表现出~5ms/cm的高电导率。高的电导率可能是由于大量酸性POH基团和水分子的共存促进了质子的快速转移。用这种水凝胶电解液制备的燃料电池可产生约160 mW/cm2的高功率密度。电极结构的优化正在进行中。使用该水凝胶还可以制备出比容量为~3F/g的双电层电容器(EDC)，具有较低的自放电率和快速充放电能力。

The sol-gel technique is widely used to prepare new functional glasses with new compositions. Our recent researches on the preparation of glasses exhibiting high proton-conductivity and their applications to the electro-devices were ingestigated. P_2O_5-SiO_2 glasses containing some metal oxides were prepared by hydrolysis of their metal alkoxides, followed by heating up to ~600℃. The obtained glasses are porous with pores smaller than few nm in diameter and contain water molecules in pores. The electrical conduction in the glass is related to the dissociation of proton from the hydroxyl bonds and the proton hopping through water molecules. PMA (phosphomolybdic acid) and PWA (phosphotungstic acid) are considered as the most dopants in the sol-gel matrix. A new class of heteropolyacid glass materials yield a high proton conductivities (10-2 S/cm) at room temperature. Though, they exhibit highly attractive fuel cell performance (~22.2 mW/cm^2) and high stability at 30℃ and relative humidity 30 %.Proton conducting phosphate hydrogels are easily derived from the reaction of water with some kinds of metaphosphate glass powders. The hydration breaks the long-chain phosphate structure in the glasses and protons break the cross-links between the chains, resulting in connection to the non-bridging oxygens. Subsequently, water molecules are hydrogen-bonded around the protons. The hydrogels show high conductivities of ~5 mS/cm at room temperature. The high conductivity is suggested to be due to the fast proton transfer promoted by coexistence of large amounts of acidic POH groups and water molecules. A fuel cell prepared using the hydrogel electrolyte generates the high power density of ~160 mW/cm^2. The optimization of the electrode structure is now being investigated. An electric double-layer capacitor (EDC) with capacitance of ~3 F/g can be also prepared by using the hydrogel, which shows low a self-discharge rate and a fast charge/discharge capability.