Abstract
Polymer composite membrane technology is promising for enhancing the performance of membrane electrode assemblies for high-temperature fuel cells. In this study, we developed a novel anhydrous proton-exchange polybenzimidazole (m-PBI) composite membrane using Al-substituted mesoporous silica (Al-MCM-41) as a proton-carrier support. The surface-substituted Al-MCM-41 formed effective proton-transport pathways via its periodic hexagonal channel and improved the proton conductivity. The proton conductivity of an m-PBI filled with 9 wt.% filler was 0.356 S cm-1 at 160 °C and 0% humidity, representing an increase of 342% compared to that of a pristine m-PBI. Further, the current density at 0.6 V and maximum power density of m-PBI composite membranes were increased to 0.393 A cm-2 and 0.516 W cm-2, respectively. The enhanced fuel-cell performance was attributed to the proton-transfer channels and H3PO4 reservoirs formed by the mesopores of the Al-MCM-41 shell. The results indicated that Al-MCM-41 is suitable with respect to the hybrid homologues for enhancing the proton transport of the m-PBI membrane.
Highlights
Mechanical instability during high-temperature operation); they are currently not a viable replacement for Nafion-based membranes
Stable operation was achieved under dry conditions at 150 °C for 600 h, which is a significant milestone in HT-PEMFC development
The main objective of this study was to develop new organic–inorganic composite membranes that are applicable to the HT-PEMFC
Summary
Mechanical instability during high-temperature operation); they are currently not a viable replacement for Nafion-based membranes. Polymer composite membrane technology is promising for enhancing the fuel-cell performance under high-temperature operating conditions. Substantial effort has been directed towards the development of acid-doped PBI membranes reinforced by nano- and mesoporous materials (e.g., silica[29,30,31], titanium oxide[32,33,34], zeolite[35], and solid acid19,36) in recent years. The main challenge for composite membranes is the harmonious architecture design of the proton-conducting groups, proton-transport channels, and acidic reservoirs. The introduction of an Al-substituted hexagonally ordered mesoporous silica (Al-MCM-41) channel into a poly(2,2′-m-(phenylene)-5,5′-bibenzimidazole) (m-PBI) membrane significantly enhanced the cell performance and durability at the high end of the operating-temperature regime. Stable operation was achieved under dry conditions at 150 °C for 600 h, which is a significant milestone in HT-PEMFC development
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