Constructing Ionic Liquid-Filled Proton Transfer Channels within Nanocomposite Membrane by Using Functionalized Graphene Oxide

Abstract

Herein, nanocomposite membranes are fabricated based on functionalized graphene oxides (FGOs) and sulfonated poly(ether ether ketone) (SPEEK), followed by being impregnated with imidazole-type ionic liquid (IL). The functional groups (acidic group or basic group) on FGOs generate strong interfacial interactions with SPEEK chains and then adjust their motion and stacking. As a result, the nanocomposite membranes possess tunable interfacial domains as determined by its free volume characteristic, which provides regulated location for IL storage. The stored ILs act as hopping sites for water-free proton conduction along the FGO-constructed interfacial channels. The microstructure at SPEEK-FGO interface governs the IL uptake and distribution in nanocomposite membrane. Different from GO and vinyl imidazole functionalized GO (VGO), the presence of acidic (-SO3H) groups confers the p-styrenesulfonic acid functionalized GO (SGO) incorporated nanocomposite membrane loose interface and strong electrostatic attraction with imidazole-type IL, imparting an enhanced IL uptake and anhydrous proton conductivity. Nanocomposite membrane containing 7.5% SGO attains the maximum IL uptake of 73.7% and hence the anhydrous conductivity of 21.9 mS cm(-1) at 150 °C, more than 30 times that of SPEEK control membrane (0.69 mS cm(-1)). In addition, SGOs generate electrostatic attractions to the ILs confined within SGO-SPEEK interface, affording the nanocomposite membrane enhanced IL retention ability.

Polymer Nanocomposite Membranes of Sulfonated Poly(Styrene‐Isobutylene‐Styrene) With Sulfonated Graphene Oxide for Fuel Cell and Protective Clothing Applications

“…The second region in the 220-280 C range is attributed to the desulfonation (i.e., loss of the sulfonic groups) of the polymer and the third (410-430 C) to the degradation of the polymer backbone [37,42,44,45]. Similar to other studies that incorporated fillers into SIBS or other polymers, the thermal stabilities of the membranes were unaffected by the incorporation of GO/sGO [11,28,30,33,37,42,47,50]. The limited enhancement in thermal stability due to GO/sGO addition could be due to the large heat conductivity of the nanosheets, which makes it difficult to slow down the heat transfer [11].…”

“…The major vibration bands associated with SO 3 H and Si − O stretching (both at ca . 1,100 cm −1 ) were overlapped by the 1,054 cm −1 band of GO and thus, could not be discriminated . Upon sulfonation, the intensity of the characteristic bands of GO was reduced.…”

“…Incorporation of sGO to the state-of-the-art Nafion ® increases the proton conductivity (σ) [34]. Previous studies with alternative polymer matrices have stated that σ increases as the GO/sGO loading increases [26][27][28][29][30]47]. Cao et al [25] showed that GO increases the ion conductivity.…”

Multiblock poly(Phenylene ether nitrile)s with pendant sulfoalkoxyl side chain for H2/air fuel cells at low humidity condition

“…In the last three decades, many research efforts have focused on the design and synthesis of aromatic ionomers as potential alternatives for PFSA membranes, such as sulfonated poly(ether ether ketone)s (SPEEKs), sulfonated poly(arylene ether sulfone)s (SPAESs), sulfonated polyimides (SPIs), and sulfonated polyphenylenes (SPPs), among others. In general, these membranes exhibited quite comparable electrochemical performance to Nafion, in terms of their proton conductivities or maximum power generations, under high relative humidity (RH) conditions.…”

Sulfonated graphene oxide‐doped proton conductive membranes based on polymer blends of highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole

“…Moreover, the intensity of diffraction peak further decreases and becomes wider with the incorporation of s‐GO. The peak intensity reduction could be interpreted by the hydrogen bonds generated between polar groups in s‐GO and the sulfonic acid groups in polymers thus destroyed the originally ordered stacking, making the nanocomposite membrane more flexible, which may be effective for improvement of ionic conductivity …”