A Critical Review of Electrolytes for Advanced Low- and High-Temperature Polymer Electrolyte Membrane Fuel Cells

Abstract

In the 21st century, proton exchange membrane fuel cells (PEMFCs) represent a promising source of power generation due to their high efficiency compared with coal combustion engines and eco-friendly design. Proton exchange membranes (PEMs), being the critical component of PEMFCs, determine their overall performance. Perfluorosulfonic acid (PFSA) based Nafion and nonfluorinated-based polybenzimidazole (PBI) membranes are commonly used for low-and high-temperature PEMFCs, respectively. However, these membranes have some drawbacks such as high cost, fuel crossover, and reduction in proton conductivity at high temperatures for commercialization. Here, we report the requirements of functional properties of PEMs for PEMFCs, the proton conduction mechanism, and the challenges which hinder their commercial adaptation. Recent research efforts have been focused on the modifications of PEMs by composite materials to overcome their drawbacks such as stability and proton conductivity. We discuss some current developments in membranes for PEMFCs with special emphasis on hybrid membranes based on Nafion, PBI, and other nonfluorinated proton conducting membranes prepared through the incorporation of different inorganic, organic, and hybrid fillers.

Scalable synthesis of pyrazine-linked conjugated microporous polymers for high-performance proton conduction

“…Initially, H 3 PO 4 @HD-CMP had a proton conductivity of 3.97 × 10 −2 S cm −1 at 303 K. When the temperature was increased to 353 K, the value of proton conductivity dramatically increased to as high as 1.05 × 10 −1 S cm −1 , which is 11 times of magnitude higher than the HD-CMP without loading H 3 PO 4 under the same conditions. Although the proton conduction of H 3 PO 4 @HD-CMP cannot be compared with some polymer films, 59–61 however, when compared with the reported proton-conducting materials under the similar conditions, such as commercial Nafion ( ca. 1.0 × 10 −1 S cm −1 at 353 K under 98% RH), 62 and other porous materials (4.8 × 10 −3 S cm −1 for aza-COF-2 H at 323 K under 97% RH; 9.04 × 10 −3 S cm −1 for H 3 PO 4 @NKCOF-10 at 353 K under 90% RH), 29,31 the remarkable conductivity still could be ranked top level (Table S2, ESI†).…”

All-Perfluorosulfonated-Ionomer Composite Membranes Containing Blow-Spun Fibers: Effect of a Thin Fiber Framework on Proton Conductivity and Mechanical Properties

“…Polymer electrolyte membranes (PEMs) are a crucial component of PEFCs, determining their performance and durability. 3 Perfluorosulfonated (PFSA) ionomers, a random copolymer consisting of semicrystalline polytetrafluoroethylene (PTFE) backbone and pendant side chains terminated by sulfonic acid groups, are commonly used as PEMs for PEFCs because of their high proton conductivity and excellent chemical stability. 4 Conventional PEMs that are used in commercial PEFCs are the PFSA ionomer membranes reinforced with porous expanded PTFE (such as Gore-Select and Nafion XL).…”

“…Recently, polymer electrolyte fuel cells (PEFCs) have become the most attractive electrochemical power converter because of their wide variety of applications, such as in automotive power, stationary power, and microelectronics. , PEFCs convert the chemical energy of hydrogen and oxygen fuels directly into electricity, affording devices with a high power density, zero CO 2 emissions, and low operating temperatures. Polymer electrolyte membranes (PEMs) are a crucial component of PEFCs, determining their performance and durability …”

“…Polymer electrolyte membranes (PEMs) are a crucial component of PEFCs, determining their performance and durability. 3 …”

Sulfonated Cobalt Metal–Organic Framework Embedded Mixed Matrix Membrane towards Fuel-Cell Applications

“…PBI is an aromatic heterocyclic macromolecule that exhibits superior thermal and mechanical stabilities at higher temperatures and resists attacks from acids and bases. 14 Poly(2,5benzimidazole) (ABPBI), a form of PBI prepared from the 3,4diaminobenzoic acid monomer, is due to the π-electron conjugation of its imidazole groups. ABPBI is a neutral polymer with noteworthy mechanical and thermal stability as well as high resistance in acid and alkaline media.…”