New Type of Nanocomposite CsH2PO4-UiO-66 Electrolyte with High Proton Conductivity

Abstract

New (1−x)CsH2PO4–xUiO-66 electrolytes with high proton conductivity and thermal stability at 230–250 °C were developed. The phase composition and proton conductivity of nanocomposites (x = 0–0.15) were investigated in detail. As shown, the UiO-66 matrix is thermally and chemically suitable for creating composites based on CsH2PO4. The CsH2PO4 crystal structure remains, but the degree of salt crystallinity changes in nanocomposites. As a result of interface interaction, dispersion, and partial salt amorphization, the proton conductivity of the composite increases by two orders of magnitude in the low-temperature range (up to 200 °C), depending on the UiO-66 fraction, and goes through a maximum. At higher temperatures, up to 250 °C, the conductivity of nanocomposites is close to the superprotonic values of the original salt at low UiO-66 values; then, it decreases linearly within one order of magnitude and drops sharply at x > 0.07. The stability of CsH2PO4-UiO-66 composites with high proton conductivity was shown. This creates prospects for their use as proton membranes in electrochemical devices.

Novel Highly Dispersed Additive for Proton-Conducting Composites

“…In addition, the intro-duction of a non-conducting matrix led to an increase in the low-temperature conductivity within a specific range of compositions, but reduced the superprotonic conductivity. The composite effects observed in this system were comparable to the conductivity values seen in the CsH 2 PO 4 -SrZrO 3 and CsH 2 PO 4 -NdPO 4 systems [48,52], but somewhat lower than for a number of the studied composite systems based on CsH 2 PO 4 [50,51,55,58]. This may be due to an insufficiently high specific surface area and the adhesion energy that determine the interface interaction.…”

“…CsH 2 PO 4 is a promising proton membrane for medium-temperature fuel cells [44,45]. Currently, investigations are focused on creating highly conductive composite and polymer electrolytes with modified salts in a larger temperature range, as well as searching for electrochemically active electrode compositions for medium temperature fuel cells based on cesium dihydrogen phosphate [46][47][48][49][50][51][52][53][54][55][56][57][58].…”