Proton-conducting membranes based on CsH₂PO₄ and copolymer of tetrafluoroethylene with vinylidene fluoride

Abstract

In this work, proton conductivity, morphology and mechanical properties of (1–x)CsH2PO4–xF-42 (x=0.05–0.3, weight ratio) membranes were investigated for the first time. Thin flexible membranes for x≥0.15 with the uniform distribution of the components were obtained by a tape casting method. Mechanical properties of the membranes were measured by Vickers microhardness tests for a low polymer content (x˂0.15), also the tensile strength for membranes with high polymer content x=0.2–0.3 were evaluated. Proton conductivity of the (1–x)CsH2PO4–xpF-42 composite polymer electrolytes decreases monotonically with increasing x due to the effect of a «conductor-insulator» percolation. The combination of conductivity, mechanical strength and hydrophobic properties of (1–x)CsH2PO4–xF-42 makes certain compositions of proton-conducting membranes (x~0.2–0.25) promising for their use in intermediate-temperature fuel cells, despite decreased conductivity.

High-Conductive CsH2PO4 Membranes with PVDF-Based Polymers Additives

“…It was shown that the P2 1 /m structure of the acid salt was retained in the composite electrolytes with different FPs (UPTFE, F42, SKF26, and PVDF) [ 27 , 31 , 32 , 33 ]. A more intensive peak in relation to the polymer can be observed on the PXRD patterns only at x ≥ 0.15 for the membranes based on FPs with a sufficiently high degree of crystallinity.…”

“…The XRD pattern for fluoroelastomer SKF26 consists of only an amorphous halo at 2Θ~17 • due to the low crystallinity owing to bulky HFP parts in a VDF structure. It was shown that the P2 1 /m structure of the acid salt was retained in the composite electrolytes with different FPs (UPTFE, F42, SKF26, and PVDF) [27,[31][32][33]. A more intensive peak in relation to the polymer can be observed on the PXRD patterns only at x ≥ 0.15 for the membranes based on FPs with a sufficiently high degree of crystallinity.…”

Copolymer of VDF/TFE as a Promising Polymer Additive for CsH2PO4-Based Composite Electrolytes

“…The properties of fluoropolymers make their use as dopants for cesium dihydrogen phosphate promising. Earlier the reports were made of “CDP—fluoropolymer” systems, where such polymers as ultrafine polytetrafluoroethylene (UPTFE), polyvinylidene fluoride (PVDF), VDF copolymers with hexafluoropropylene (SKF-26), with tetrafluoroethylene (F-42), were used as additives [ 26 , 28 , 33 , 34 ]. Specifically, fluoroplastic-2M, with a commercial name F-2M, can be used as it consists of modified PVDF composition.…”