Overcoming undesired fuel crossover: Goals of methanol-resistant modification of polymer electrolyte membranes

With ever-increasing energy demand and an eagerness for sustainable and green energy, the Chinese government has deployed policies to support methanol fuel applications. The direct methanol fuel cell (DMFC) in the role of a notable energy conversion technology has immense potential in the era of green development in the world. One of the most significant obstacles hindering the commercial application of such a cell is methanol crossover. Reducing methanol permeability of the polymer electrolyte membrane (PEM) is a fundamental way to lessen or annihilate methanol crossover, which, in turn, stimulates research for gaining an in-depth understanding and building a development strategy for methanol-permeation resistant PEM. To provide engineers and researchers with a basis in their efforts to increase the DMFC efficiency, this paper reviews critical strategies in developing methanol-permeation resistant PEM and discusses prominent examples in this area, including the latest design scheme of a zero-fuel-crossover proton-selective membrane. Furthermore, the defects of the existing methanol-permeation testing methods are evaluated based on the difference between the testing environment and application environment of the PEM, and a new method for measuring methanol permeability with closer value to the actual condition proposed. Besides, the current challenges and future opportunities of methanol resistant membranes are presented. This work will serve as a guide for the DMFC research community in selecting a suitable PEM modified method.