Sulfonated MOF‑Enhanced Nafion Membranes for High‑Temperature, Durable Proton Exchange Membrane Water Electrolysis

ABSTRACT High‐temperature proton exchange membrane water electrolysis (HT‐PEMWE) is a promising strategy for low‐energy, high‐efficiency hydrogen production. However, practical implementation relies critically on the development of novel PEMs that simultaneously offer high proton conductivity and long‐term stability at high temperatures. While metal–organic frameworks (MOFs) have been widely investigated as high‐performance proton‐conducting materials, their specific incorporation into Nafion matrices for HT‐PEMWE remains largely unexplored. In this work, we designed and fabricated a sulfonated MOF‐reinforced Nafion (S/N‐Nafion) composite membrane. The S/N‐Nafion membrane achieved a proton conductivity of 154.7 mS cm −1 at 100 °C, which is twice that of recast Nafion (75.6 mS cm −1 ), while also possessing excellent mechanical strength and dimensional stability at elevated temperatures. When used as the solid electrolyte, an electrolyzer with S/N‐Nafion reached only 1.59 V at 120 °C and 3.0 A cm −2 , which is 120 mV lower than recast Nafion (1.71 V) under the identical conditions. Moreover, during a 300‐h durability test at 120 °C and 1.0 A cm −2 , the S/N‐Nafion‐PEMWE exhibited an extremely low voltage decay rate of 6.0 µV h −1 . These results underscore the immense potential of the S/N‐Nafion membrane for enabling highly efficient and stable high‐temperature electrolytic hydrogen production.