Synthesis and Properties of Polysilsesquioxane Functionalized Poly(p‐terphenyl‐co‐N‐methyl‐4‐piperidine) Membrane for High Temperature Proton Exchange Membrane Fuel Cells

Abstract The development of high‐performance, cost‐effective high temperature polymer electrolyte membranes (HT‐PEMs) is a great challenge for HT‐PEM fuel cells. In this study, a new HT‐PEM of polysilsesquioxane functionalized poly(p‐terphenyl‐co‐N‐methyl‐4‐piperidine) (PTP‐CPTMS) is reported. Owing to the incorporation of the polysilsesquioxane network, the PTP‐CPTMS membrane demonstrates an excellent phosphoric acid (PA) doping capacity and controlled swelling, compared to the benchmarks, that is, pristine PTP membrane and propyl group grafted PTP membrane (PTP‐C3). As a result, the PTP‐CPTMS/208%PA membrane exhibits a low volume swelling of 77%, a high conductivity of 0.070 S cm⁻¹ at 180 °C and a satisfactory tensile strength of 4.9 MPa at room temperature. Based on the above membrane, the H₂‐O₂ single cell is assembled and displays a steadily increased peak power density up to 220 °C, which is 769 mW cm⁻² without the need for external humidification or backpressure. This work provides a kind of polysilsesquioxane functionalized HT‐PEMs, which hold substantial potential for application in HT‐PEM fuel cells.