In the present work, a series of poly(phenylene oxide) (PPO) based uncross-linked and cross-linked anion exchange membranes (AEMs) with bis-imidazolium cations were synthesized and characterized. Compared with cross-linked AEMs, uncross-linked membranes with similar ion exchange capacities showed a much higher water uptake and swelling degree. Cross-linked membranes showed vastly improved alkaline stability, oxidation stability and mechanical properties compared with uncross-linked membranes due to the effective cross-linked structure, and a well-developed hydrophilic/hydrophobic phase separated morphology was observed for cross-linked membranes by atomic force microscopy (AFM). A single cell with a cross-linked membrane (Cross-Im-PPO-75) showed a maximum power density of 212.45 mW cm−2. Considering the enhanced alkaline stability and mechanical properties, the cross-linked PPO membranes with bis-imidazolium cations are promising AEM materials for alkaline exchange membrane fuel cells.

Bis-imidazolium based poly(phenylene oxide) anion exchange membranes for fuel cells: the effect of cross-linking

Proton transport in nanochannels under humid conditions is crucial for the application in energy storage and conversion. However, existing materials, including Nafion, suffer from limited conductivity of up to 0.2 siemens per centimeter. We report a class of membranes assembled with two-dimensional transition-metal phosphorus trichalcogenide nanosheets, in which the transition-metal vacancies enable exceptionally high ion conductivity. A Cd0.85PS3Li0.15H0.15 membrane exhibits a proton conduction dominant conductivity of ~0.95 siemens per centimeter at 90° Celsius and 98% relative humidity. This performance mainly originates from the abundant proton donor centers, easy proton desorption, and excellent hydration of the membranes induced by cadmium vacancies. We also observed superhigh lithium ion conductivity in Cd0.85PS3Li0.3 and Mn0.77PS3Li0.46 membranes.

CdPS3 nanosheets-based membrane with high proton conductivity enabled by Cd vacancies.

Phosphoric acid-doped poly(ether sulfone benzotriazole) for high-temperature proton exchange membrane fuel cell applications

High-temperature proton exchange membrane fuel cells based on phosphoric acid-doped polybenzimidazole membranes are a technology characterized by simplified construction and operation along with possible integration with, e.g., methanol reformers. Significant progress has been achieved in terms of key materials, components and systems. This review is devoted to updating new insights into the fundamental understanding and technological deployment of this technology. Polymers are synthetically modified with basic functionalities, and membranes are improved through cross-linking and inorganic–organic hybridization. New insights into phosphoric acid along with its interactions with basic polymers, metal catalysts and carbon-based supports are recapped. Recognition of parasitic acid migration raises acid retention issues at high current densities. Acid loss via evaporation is estimated with respect to the acid inventory of membrane electrode assembly. Acid adsorption on platinum surfaces can be alleviated for platinum alloys and non-precious metal catalysts. Binders have been considered a key to the establishment of the triple-phase boundary, while recent development of binderless electrodes opens new avenues toward low Pt loadings. Often ignored microporous layers and water impacts are also discussed. Of special concern are durability issues including acid loss, platinum sintering and carbon corrosion, the latter being critical during start/stop cycling with mitigation measures proposed. Long-term durability has been demonstrated with a voltage degradation rate of less than 1 μV h−1 under steady-state tests at 160 °C, while challenges remain at higher temperatures, current densities or reactant stoichiometries, particularly during dynamic operation with thermal, load or start/stop cycling.

Polybenzimidazole-Based High-Temperature Polymer Electrolyte Membrane Fuel Cells: New Insights and Recent Progress

Simultaneously enhancing ionic conduction and mechanical strength of poly(ether sulfones)-poly(vinyl pyrrolidone) membrane by introducing graphitic carbon nitride nanosheets for high temperature proton exchange membrane fuel cell application

1,2,4-Triazole functionalized poly(arylene ether ketone) for high temperature proton exchange membrane with enhanced oxidative stability

Conventional fillers have limitations on the modification of proton exchange membranes because of differences in the sizes and physicochemical properties of matrix molecules. Designing skeleton molecules is a vital way to address the limitations by enabling precise distribution in the matrix and inducing automatic nanoscale aggregation and separation of hydrophilic–hydrophobic phases. In this work, a novel SDF-PAEK polymer was synthesized with a rigid hydrophobic backbone, short high-density trifluoromethyl side chains and long flexible aliphatic pendant side chains as a skeleton molecule for the Nafion membrane. Due to the unique molecular interaction selectivity during the membrane formation process, SDF-PAEK automatically matches the Nafion molecular conformation by self-assembly. Combining an improved solution formulation and membrane-casting method, the degree of composition can therefore rise to 20%, which can effectively reduce the cost. Morphological studies show that there is a certain degree of bicontinuous phase microcrystalline domains, and the proton transport channels are highly concentrated. In contrast to the Nafion membrane, SDF-PAEK@Nafion-15% exhibits better performances with higher selectivity (9.73 × 104 S s cm−3) and single-cell maximum power density (PDmax–139 mW cm−2, at 80 °C), which demonstrates the feasibility of SDF-PAEK as a novel PEM skeleton molecule for fuel cell applications.

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Enhancing the selectivity of Nafion membrane by incorporating a novel functional skeleton molecule to improve the performance of direct methanol fuel cells

Enhancing proton conductivity and methanol resistance of SPAEK membrane by incorporating MOF with flexible alkyl sulfonic acid for DMFC

The key challenge for the use of polymer electrolytes is to realize a high ionic conductivity without scarifying their mechanical performance. Herein, we report a facile strategy to prepare a nanos...

https://www.chinesechemsoc.org/doi/pdf/10.31635/ccschem.021.202000608

Jialin Li

Papers

1,2,4-Triazole functionalized poly(arylene ether ketone) for high temperature proton exchange membrane with enhanced oxidative stability

Enhancing the selectivity of Nafion membrane by incorporating a novel functional skeleton molecule to improve the performance of direct methanol fuel cells

Enhancing proton conductivity and methanol resistance of SPAEK membrane by incorporating MOF with flexible alkyl sulfonic acid for DMFC

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Understanding of hydrocarbon ionomers in catalyst layers for enhancing the performance and durability of proton exchange membrane fuel cells