Phosphoric acid doped composite membranes from poly (2,5-benzimidazole) (ABPBI) and Cs_xH_(3-x)PW_(12)O_(40)_/GeO_2 for the high temperature PEMFC

摘要

Poly (2,5-benzimidazole) (ABPBI) was prepared from 3,4-diaminobenzoic acid via a polymerization reaction. This benzimidazole polymer has a good thermal stability at the desired temperatures of 140-200 ℃. The membranes of ABPBI are readily to be doped with phosphoric acid at room temperature show very promising proton conductivity. A multifunctional catalyst Cs_xH_(3-x)PW_(12)O_(10)/CeO_2 was prepared to mitigate the free radical attack to improve the chemical stability in fuel cell environment. Cs_xH_(3-x)PW_(12)O_(10)/CeO_2 nano-particles synthesized by solution-based hydrothermal method and two-step impregnation method were dispersed uniformly into the resin, and then the composite membrane was prepared using solution-cast method. The particles prepared were characterized by X-ray powder diffraction (XRD) and SEM evaluates the crystallite size, distribution of the nano-particles and the crystal structure. The chemical stability of membrane was investigated via ex situ Fenton test. In the durability tests, the weight loss rate (WLR) reduced 75% by adding Cs_xH_(3-x)PW_(12)O_(10)/CeO_2 nanoparticles into the ABPBI membrane, besides, it could improve proton conductivity up to 0.2 S cm~(-1) in a temperature range of 140-180 ℃ under different relative humidity. The power density of the cell with the composite membrane was up to 530 mW cm~(-2).