Crosslinked Sulfonated Polyphenylsulfone (CSPPSU) Membranes for Elevated-Temperature PEM Water Electrolysis

Abstract

In order to reduce the burden on the environment, there is a need to develop non-fluorinated electrolyte membranes as alternatives to fluorinated electrolyte membranes, and water electrolysis using hydrocarbon-based electrolyte membranes has been studied in recent years. In this paper, for the first time, we report elevated-temperature water electrolysis properties of crosslinked sulfonated polyphenylsulfone (CSPPSU) membranes prepared by sulfonation and crosslinking of hydrocarbon-based PPSU engineering plastics. The sulfone groups of the CSPPSU membrane in water were stable at 85 °C (3600 h) and 150 °C (2184 h). In addition, the polymer structure of the CSPPSU membrane was stable during small-angle X-ray scattering (SAXS) measurements from room temperature to 180 °C. A current density of 456 mA/cm2 was obtained at 150 °C and 1.8 V in water electrolysis using the CSPPSU membrane and IrO2/Ti as the catalytic electrode for oxygen evolution. The stability of the CSPPSU membrane at elevated temperatures with time was evaluated. There were some issues in the assembly of the CSPPSU membrane and the catalytic electrode. However, the CSPPSU membrane has the potential to be used as an electrolyte membrane for elevated-temperature water electrolysis.

Water Electrolysis toward Elevated Temperature: Advances, Challenges and Frontiers

“…Additionally, cross-linked sulfonated poly(phenylene sulfone) (CSPPSU) displayed an excellent proton conductivity of 163 mS•cm −1 at 120 °C under humidified conditions (90% RH) 260 and stability during 2184 h of exposure to water at 150 °C. 261 Chitosan (CS) combined with phosphorylated GO (P-GO) also showed applicability at elevated working temperature at 160 °C, although an inadequate proton conductivity of 5.79 mS•cm −1 occurred under anhydrous conditions, which could be resolved by increasing the amount of proton-conducting channels in humidified environments. 262 Analogous to that of PBI-based membranes, the proton conductivity of polymers with basic sites can be improved through PA doping.…”

“…Materials and performance of membranes for ET-PEMECs (including Nafion-based membranes, − ,− PA-doped PBI-based membranes ,− ,− ,,,,,− and other polymer electrolyte membranes − ,− ).…”

“…Currently, existing ET-PEMECs primarily operate at 100–150 °C, and Table lists the corresponding materials and performance parameters. In this regard, working pressure is a significantly decisive factor, and ET-PEMECs operating with liquid water at an elevated pressure of 2.5–5 bar ,− display notably superior performance over those operating with steam at a lower pressure. ,− In reality, evident performance deterioration was extensively observed under increasing working temperature while maintaining atmospheric pressure, ,, which is contradictory to the supposed enhanced thermodynamics and kinetics. As shown in Figure (a), an extremely high current density of 3000 mA·cm –2 was realized with a lower voltage of 1.86 V at 120 °C and 3 bar, while Figure (b) illustrates the utilized test system for operation and measurements at elevated working temperatures.…”

Review and Prospects of PEM Water Electrolysis at Elevated Temperature Operation

“…[99] Low T g (with respect to the operation window considered for ET) is characteristic for conventional PFSAs. [74] Non-Fluorinated Membranes: In view of the limited mechanical stability of fluorinated electrolyte membranes at ET, Kim and Ohira [100] studied cross-linked sulfonated polyphenylsulfone (CSPPSU) material as an alternative. In this case, the stabilities were assessed by placing the membranes in water at 85 °C and in an autoclave at 150 °C for a prolonged period of time and compared the ion-exchange capacity (IEC), WU, and conductivity before and after the test period.…”

“…As concluded by Jensen et al, [53] lower voltages and higher current densities seem to cur-Figure 12. Shaded regions capture the best performances obtained for steam operation (up to a temperature of 170 °C) [49,[100][101][102][103][104] and liquid operation (studied in the temperature range of 100-140 °C and under a pressure up to 5.5 bar abs on the anode side). [18,22,55,[85][86][87]89,95,98,113,115,127,132,149] rently favor operation with liquid water (signified by the yellow shaded area).…”