Hydroxide exchange membranes towards water electrolysis and fuel cells: A review on the recent advances, challenges and opportunities

Abstract

Hydroxide exchange membranes (HEMs) featuring high-performance and low-cost have attracted numerous attention due to their potential in water electrolysis and fuel cell applications. The main challenges of their relatively low ionic conductivity and insufficient stability have been alleviated by the rapid advancements in the latest years, especially with the emerging new materials with fine regulation of ion transport channels and the molecular design of the nonvolatile HEM in the operation condition. This review provides a comprehensive overview of the latest advancements in HEMs, focusing on the mechanism, influencing factors, and mitigation approaches of ionic conductivity and stability. In particular, we systematically overview the importance and regulation approaches of ion transport channels, including the channel size, channel orientation, and newly emerging membranes with intrinsic channels. Moreover, the influences of the operation conditions in practical devices on the performance of HEM are also overviewed and discussed. By offering insights into the fundamental mechanism, design strategies of ion transport channel and polymer chemistry, discussion of the challenges of each material, and potential opportunities, this work will contribute to the development of advanced HEM for hydrogen-electricity conversion devices.