Abstract
The has been a strong demand for eco-friendly energy conversion and storage devices.1 Anion exchange membrane water electrolyzers (AEMWEs) which produce pure hydrogen and oxygen by water splitting, have gained considerable attention owing to their high efficiency and possible utilization of low-cost nonprecious metals (e.g., Ni, Co, and Fe) as electrocatalysts, separators, and gas diffusion layers.1,2 Anion exchange membranes (AEMs) as an indispensable key component in AEMWEs play several crucial roles including hydroxide ion and water transportation as well as gas separation.1,2 Furthermore, AEMs should possess multiple characteristics such as excellent thin membrane forming capability, mechanical and dimensional stability (or low swelling) in water, and alkaline stability under operating conditions.2 In this work,3 we investigate the effect of cross-linking on partially fluorinated AEMs tethered with trimethylpropyl side chain via radical-mediated cross-linking reaction (Figure 1). The one-pot cross-linking and quaternization reactions were successful as confirmed through NMR spectra. Transparent membranes (xQPAF-C3-VB) were obtained with 9.1-36.0% degree of cross-linking (DOC). TEM images revealed smaller hydrophilic/hydrophobic phase-separated morphology. As well as the suppressed water uptake in the cross-linked membranes, the hydroxide ion conductivity decreased slightly. Among them, xQPAF-C3-VB with 17.4% DOC (ion exchange capacity of 1.16 meq g-1) exhibited the highest hydroxide ion conductivity (56 mS cm-1 at 30 ℃) which was comparable to that of the pristine (uncross-linked) membrane. In addition, the cross-linking strategy helped to improve the thermomechanical properties resulting in higher glass transition temperature. The cross-linked xQPAF-C3-VB was utilized as membrane in AEMWEs to achieve high efficiency (74%) and reasonable performance (1.67 V at 1.0 A cm-2) (Figure 1).
Published Version
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