Ionoelastomers at Electrified Interfaces: Differential Electric Double-Layer Capacitances of Cross-Linked Polymeric Ions and Mobile Counterions
Ionoelastomers at Electrified Interfaces: Differential Electric Double-Layer Capacitances of Cross-Linked Polymeric Ions and Mobile Counterions
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DOI：
10.1021/acs.macromol.3c01092
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发表时间：
2023-09
期刊：
影响因子：
5.5
通讯作者：
Heewoon Shin;Jowon Shin;R. C. Hayward;H. Kim
中科院分区：
文献类型：
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作者：
Heewoon Shin;Jowon Shin;R. C. Hayward;H. Kim
离子弹性体（IEs）仅由聚合离子液体（pil）的交联网络组成，由于其独特的结合了离子液体（ILs）的电化学性能和聚合物网络的固态弹性性能，在各种电化学应用中得到了广泛的关注。然而，IEs在通电表面的双电层（EDL）的结构尚不清楚，特别是当考虑到其中一种离子是共价结合在交联聚合物网络上时。在这里，我们研究了交联聚合物离子和反离子在IEs中的差异EDL电容。制备了一对极性相反的IEs；具有交联咪唑阳离子和游离双（三氟甲基磺酰）亚胺（TFSI）阴离子的聚阳离子IE和具有交联磺酰亚胺阴离子和游离1-乙基-3-甲基咪唑（EMIM）阳离子的聚阴离子IE。通过施加两个比表面积大的电极，交联聚合物离子和移动反离子的EDL电容可以解耦。我们发现，在聚阴离子和聚阳离子离子中，固定离子的EDL电容都低于反离子的EDL电容，导致电容响应高度不对称，取决于施加电压的符号。在没有交联的情况下，我们观察到聚合物离子和反离子的EDL电容相似，这表明在IEs中交联网络的弹性能量限制了聚合物离子在带电表面重排的自由，从而降低了EDL电容。
Ionoelastomers (IEs), consisting solely of cross-linked networks of polymerized ionic liquids (PILs), have gained attention for use in various electrochemical applications due to their unique combination of the electrochemical properties of ionic liquids (ILs) and the solid-state elastic properties of the polymer networks. However, the structure of the electric double layer (EDL) of IEs at electrified surfaces is not well understood, especially when considering that one of the ionic species is covalently bound to the cross-linked polymer network. Herein, we investigate the differential EDL capacitances of cross-linked polymeric ions and counterions in IEs. A pair of IEs with opposite polarity are prepared; the polycationic IE with cross-linked imidazolium cations and free bis(trifluoromethyl sulfonyl)imide (TFSI) anions and the polyanionic IE with cross-linked sulfonimide anions and free 1-ethyl-3-methylimidazolium (EMIM) cations. By applying two electrodes with a large contrast in surface area, the EDL capacitances of the cross-linked polymeric ions and the mobile counterions can be decoupled. We find that the EDL capacitances of the fixed ions are lower than that of the counterions in both the polyanion and polycation IEs, resulting in a highly asymmetric capacitance response depending on the sign of the applied voltage. Without cross-linking, we observe similar EDL capacitances for polymeric ions and counterions, suggesting that the elastic energy of the cross-linked networks in IEs restricts the freedom of polymeric ions to rearrange at the electrified surfaces, thereby reducing the EDL capacitance.