Abstract
Polymer electrolyte membrane fuel cells (PEMFCs) expect a promising future in addressing the major problems associated with production and consumption of renewable energies and meeting the future societal and environmental needs. Design and fabrication of new proton exchange membranes (PEMs) with high proton conductivity and durability is crucial to overcome the drawbacks of the present PEMs. Acid-doped polybenzimidazoles (PBIs) carry high proton conductivity and long-term thermal, chemical, and structural stabilities are recognized as the suited polymeric materials for next-generation PEMs of high-temperature fuel cells in place of Nafion® membranes. This paper aims to review the recent developments in acid-doped PBI-based PEMs for use in PEMFCs. The structures and proton conductivity of a variety of acid-doped PBI-based PEMs are discussed. More recent development in PBI-based electrospun nanofiber PEMs is also considered. The electrochemical performance of PBI-based PEMs in PEMFCs and new trends in the optimization of acid-doped PBIs are explored.
Highlights
Fuel cells, as attractive energy-conversion devices, are able to directly convert chemical energy stored in hydrogen and other simple organic substances into electrical energy via an electrochemical reaction
Given the doping level of where Ea is the activation energy, σ0 is the pre-exponential factor of proton conductivan acid-doped PBI membrane, proton conductivity increases with temperature and relative humidity (RH)
With phosphoric acid as a general acid agent for doping PBI membranes, the activation energy decreases with increasing doping level, as a result of excess phosphoric acid in the level of an acid-doped PBI membrane, proton conductivity increases with temperature and RH
Summary
As attractive energy-conversion devices, are able to directly convert chemical energy stored in hydrogen and other simple organic substances into electrical energy via an electrochemical reaction. Low fuel gas permeability; Superior electrochemical and thermal stabilities in a harsh environment; Excellent mechanical properties in both dry and hydrated states; Sufficient water uptake and moderate swelling; Outstanding long-term durability (>10 years) in the operating PEMFCs; Low cost (
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