Ti₃C₂T_x Filler Effect on the Proton Conduction Property of Polymer Electrolyte Membrane

Abstract

Conductive polymer electrolyte membranes are increasingly attractive for a wide range of applications in hydrogen-relevant devices, for instance hydrogen fuel cells. In this study, two-dimensional Ti3C2Tx, a typical representative of the recently developed MXene family, is synthesized and employed as a universal filler for its features of large specific surface area, high aspect ratio, and sufficient terminated -OH groups. The Ti3C2Tx is incorporated into polymer matrix to explore its function on membrane microstructure and proton conduction property. Both phase-separated (acidic Nafion and sulfonated poly(ether ether ketone)) and non-phase-separated (basic chitosan) polymers are utilized as membrane matrixes. The microstructures, physicochemical properties, and proton conduction properties of the membranes are extensively investigated. It is demonstrated that Ti3C2Tx generates significant promotion effect on proton conduction of the composite membrane by facilitating both vehicle-type and Grotthuss-type proton transfer, yielding several times increased proton conductivity for every polymer-based composite membrane under various conditions, and the composite membrane achieves elevated hydrogen fuel cell performance. The stable Ti3C2Tx also reinforces the thermal and mechanical stabilities of these composite membranes. Since the MXene family includes more than 70 members, this exploration is expected to open up new perspectives for expanding their applications, especially as membrane modifiers and proton conductors.

Sulfonic Acid Functionalized Chitosan as a Sustainable Component for Proton Conductivity Management in PEMs

“…Above comparisons point out that the Nafion‐CS‐SO 3 H composites of our work have enhanced performance in terms of proton conductivity which persist in the whole range of % RH levels (at least up to 80 °C and down to 30 % RH) (Table ). These improvements are rather difficult to achieve, only a limited number of efficient membrane/additive examples exist including sophisticated and recent synthetic 2D conductive fillers such as MXenes in polymer matrixes . It is also highlighted that composite membranes with 5 wt % native chitosan presents lower values compared to that of Nafion/5%wt CS‐SO 3 H, in agreement with the literature results .…”

Mechanotribological Aspects of MXene‐Reinforced Nanocomposites

“…[5,28] MXenes could significantly affect the growth of spherulites as well as the crystallization behavior of polymeric materials. [68,142] According to Liu et al, [57] the addition of Ti 3 C 2 T x considerably changed the glass transition temperature (T g ); further, the mechanical strength improved by 23% from 104.6 MPa for the neat Nafion to 128.4 MPa for the composite sample most probably due to the high aspect ratio and the OH termination groups of MXene sheets providing hydrogen-bonding interactions. MXene's functional groups such as O 2 , OH, and F, offer a quite better affinity with polymeric molecules than graphene.…”

“…To date, most of the MXene-reinforced polymer nanocomposites have been produced by solution mixing techniques due to the hydrophilic nature of MXene nanosheets endowed by the functional groups. In this method, MXene nanomaterials are commonly dispersed in a polar media like water, [57,58] dimethylsulfoxide (DMSO), [59] N,N-dimethylformamide (DMF), [60] among others; polymer material could also be dissolved in the same dispersant or in another one with mutual solubilities. [38] These solutions comprising the polymer and MXene are then mixed and blended together to generate a homogenous slurry of MXene composites.…”

“…It should be noted that the solubility of MXene in nonpolar polymers or those with weakly polar groups is still challenging and hence a suitable surface premodification needs to be adopted for enhancing dispersibility. [61,62] As yet, different MXene nanomaterials have pervaded in many polymers such as polyurethane, [62] polyfluorenes, [63] polylactic acid, [64] polyethyleneimine, [65] Nafion, [57] polyacrylamide, [38,66] cellulose, [8,67] polyethylene oxide, [68] polyvinyl alcohol, [69,70] chitosan, [71] polybenzimidazole, [72] polyvinylidene fluoride (PVDF), [60] and polyacrylate acrylic resin, [73] etc. Although solution mixing is a simple operation taking the advantage of hydrophilicity of MXene nanomaterials, a few serious drawbacks such as the generation of inordinate amount of environmental wastes, poor mechanical properties associated with the ensued composites as well as the laborious evaporation of solvents usually constrain the use of solution mixing.…”

Biocompatible and Biodegradable Functional Polysaccharides for Flexible Humidity Sensors

“…Namely, the proton current in the degradable biocomposite film at 75%RH is threefold higher than that at 65%RH. At 85%RH, more water was adsorbed on the surface of the degradable biocomposite film, forming more hydrogen-bonded proton wires, which increased proton transfer, thus increasing the current [24]. To rationalize the experimental results and estimate the effects of humidity on the proton density in the channels of the degradable biocomposite film, we simulated changes in the proton charge density in degradable biocomposite film using the finite element method (FEM) (detailed parameters are provided in Materials and Methods).…”