The impact of imidazolium with steric hindrance on the dissociation of phosphoric acid and the performance of high-temperature proton exchange membranes

The low conductivity and poor stability of high-temperature proton exchange membranes (HT-PEMs) are still the main reasons limiting the practical application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, a strategy of blending polyimidazolium (P-Im) with strong steric...

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Published inJournal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 36; pp. 24499 - 24507
Main Authors Sun, Xi, Yu, Huiting, Guan, Jiayu, Zhang, Bin, Zheng, Jifu, Li, Shenghai, Zhang, Suobo
Format Journal Article
LanguageEnglish
Published Cambridge Royal Society of Chemistry 18.09.2024
Subjects
Addition polymerization
Benzimidazoles
Blending effects
Bonding strength
Conduction
Conductivity
Functional groups
High temperature
Hydrogen bonding
Ion association
Ionic interactions
Leaching
Low conductivity
Membranes
Phosphoric acid
Polymers
Proton conduction
Proton exchange membrane fuel cells
Protons
Stability
Steric hindrance
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Summary:The low conductivity and poor stability of high-temperature proton exchange membranes (HT-PEMs) are still the main reasons limiting the practical application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, a strategy of blending polyimidazolium (P-Im) with strong steric effect in HT-PEMs is proposed to accelerate proton conduction and improve operating stability. For one thing, the steric hindrance facilitates the formation of stable ion-association complexes between imidazolium and dihydrogen phosphate, promoting the dissociation of phosphoric acid (PA). For another, it helps to enhance acid–base interaction and hydrogen bonding between P-Im and PA, thus inhibiting the leaching of PA. The proton conductivity of the blend membrane reaches 0.149 S cm −1 at 200 °C, which is 1.16 times higher than that of the poly[2,2′-( p -oxydiphenylene)-5,5′-benzimidazole] (OPBI) membrane with a 24.1% lower PA uptake under the same conditions. And the corresponding peak power density is 746 mW cm −2 without backpressure. This work presents a novel approach to enhance proton conduction efficiency in HT-PEMs from the perspective of accelerating PA dissociation by introducing additional ionic interactions and regulating the steric effect of functional groups in the polymer matrix.
ISSN:2050-7488
2050-7496
DOI:10.1039/D4TA03948C