ulfonated poly(ether sulfone) (SPES)/boron phosphate (BPO_4) composite membranes for high-temperature proton-exchange membrane fuel cells

摘要

A new series of sulfonated poly(ether sulfone) (SPES)/boron phosphate (BPO_4) composite membranes for proton-exchange membrane fuel cells (PEMFCs) applications, with a BPO_4 content up to 40 wt%, were prepared by a sol-gel method using tripropylborate and phosphoric acid as precursors. Compared to a pure SPES membrane, BPO_4 doping in the membranes led to a higher thermal stability and glass-transition temperature (Tg) as revealed by TGA-FTIR, DSC and DMTA. Water uptake and oxidative stability were significantly increased by increasing the content of BPO_4. At both operating temperature conditions, namely 20 ℃ and 100 ℃, the tensile strength of all the composite membranes were lower than that of the SPES membrane. However, even when the content of BPO_4 was as high as 30%, the composite membrane still possessed strength similar to the Nation 112 membrane. SEM-EDX indicated that the BPO_4 particles were uniformly embedded throughout the SPES matrix, which may facilitate proton transport. Proton conductivities increased from 0.0065 to 0.022 S cm~(-1) at room temperature as BPO4 increased from 0 to 40%. The conductivities also increased with the temperature. The SPES/BPO_4 composite membrane is a promising candidate for PEMFCs applications, especially at higher temperatures.