Solvent-free nanocomposite proton-conducting membranes composed of cesium salt of phosphotungstic acid doped PVDF–CTFE/PEO blend

Abstract

In this research, novel nanocomposite membranes were prepared using polymer blend of polyethylene oxide (PEO) and polyvinylidene fluoride-chloro tetrafluoro ethylene (PVDF-CTFE) copolymer with cesium salt of phosphotungstic acid (Cs 2.5 H 0.5 PWO 40 ) as proton conductor. Nanocomposite membranes were prepared by solventfree procedure. The DSC studies show a decrease in crystalinity of polymer matrix with increasing PEO to PVDF-CTFE proportional ratio and the filler. The TGA studies show that membranes are stable up to 180°C. The TGA also indicates that addition of cesium salt of phosphotungstic acid increases the thermal stability of membranes. The SEMs exhibit that membranes are nonporous and the additive components are homogenously dispersed. Conductivity tests for membranes were carried out in the range of 25-100°C in dry and hydrated states. Results show that by increasing the temperature, membranes conductivities are increased. In dry state, except at the temperature of 45°C, membranes which have the highest crystalinity, have the highest conductivity. The alteration of the conductivity in the range of temperatures in dry condition may be attributed to segmental motion of polymer which resulted in proton hopping from one site to another or increasing free volume for proton motion. In fully hydrated state, dynamic equilibrium between different proton moieties determines the mode of proton conductivity which can be described by Grothuss mechanism. In the presence of water molecule, the free proton may be formed. The conductivity for the membrane in hydrated state with the blend ratio of PVDF:PEO=95:5 w/w and 10% addition of cesium salt of phosphotungstic acid at the temperature of 90°C is 1.05×10 −4 S cm −1 .

Methanol and proton transport through chitosan‐phosphotungstic acid membranes for direct methanol fuel cell

“…Heteropolyacids (HPAs) are well‐known superionic proton conductors in the fully hydrated states, and are widely used as proton conductor solid electrolytes as well as to enhance proton conductivity of CS membranes 24‐27 . Cui et al proposed polyelectrolyte complexes of CS and an HPA (phosphotungstic acid [PTA]) to be used as PEM in DMFCs demonstrating good swelling properties, good proton conductivity, and low methanol permeability, 28 as also done by Wu et al whose membranes allowed to get a peak power density of 16 mW cm −2 29 .…”

“…Heteropolyacids (HPAs) are well-known superionic proton conductors in the fully hydrated states, and are widely used as proton conductor solid electrolytes as well as to enhance proton conductivity of CS membranes. [24][25][26][27] Cui et al proposed polyelectrolyte complexes of CS and an HPA (phosphotungstic acid [PTA]) to be used as PEM in DMFCs demonstrating good swelling properties, good proton conductivity, and low methanol permeability, 28 as also done by Wu et al whose membranes allowed to get a peak power density of 16 mW cm −2 . 29 On the other hand, HPAs can facilitate the oxidative removal of CO ads poisoning species for methanol oxidation and desorption of O ads species for oxygen reduction reaction on Pt catalysts, 30,31 thus their presence at the electrode/polymer electrolyte interface can reduce the kinetic losses due to the cell reaction.…”

Tailoring poly(vinylidene fluoride-co-chlorotrifluoroethylene) microstructure and physicochemical properties by exploring its binary phase diagram with dimethylformamide

“…The pseudo‐block structure of PVDF‐CTFE offers feasibility for possible grafting modification via atom transfer radical polymerization (ATRP) preserving the high mechanical, thermal, and chemical stabilities . Intense research efforts are underway on the use of the materials for electrical energy storage, as high energy materials, and the development of gel electrolyte membranes. In particular, its key features for energy storage application are its high ionic conductivity and good compatibility with lithium metal electrodes …”