Phosphoric acid doped proton exchange membranes often experience performance degradation above 200 °C due to membrane creeping and phosphoric acid evaporation, migration, dehydration, and condensation. To address these issues, here we present gel-state polybenzimidazole membranes with double cross-linked three-dimensional layered structures via a polyphosphoric acid sol-gel process, enabling stable operation above 200 °C. These membranes, featuring proton-conducting cross-linking phosphate bridges and branched polybenzimidazole networks, effectively anchor and retain phosphoric acid molecules, prevent 96% of its dehydration and condensation, improve creep resistance, and maintain excellent proton conductivity stability. The resulting membrane, with superior through-plane proton conductivity of 0.348 S cm⁻¹, delivers outstanding peak power densities ranging from 1.20–1.48 W cm⁻² in fuel cells operated at 200-240 °C and a low voltage decay rate of only 0.27 mV h⁻¹ over a 250-hour period at 220 °C, opening up possibilities for their direct integration with methanol steam reforming systems.

磷酸掺杂质子交换膜在 200 °C 以上时，由于膜蠕变和磷酸蒸发、迁移、脱水和冷凝，常常会出现性能下降。为了解决这些问题，我们在这里通过多磷酸溶胶-凝胶工艺提出了具有双交联三维层状结构的凝胶态聚苯并咪唑膜，能够在200℃以上稳定运行。这些膜具有质子传导交联磷酸酯桥和支化聚苯并咪唑网络，可有效锚定和保留磷酸分子，防止96%的脱水和缩合，提高抗蠕变性，并保持优异的质子传导稳定性。由此产生的膜具有 0.348 S cm ^-1的卓越平面质子电导率，在 200-240 °C 运行的燃料电池中可提供 1.20-1.48 W cm ^-2的出色峰值功率密度，电压衰减率仅为在 220 °C 下 250 小时内为0.27 mV h ^{−1 ，这为它们与甲醇蒸汽重整系统直接集成提供了可能性。}