Poly(vinyl alcohol) (PVA) is a biodegradable, water-soluble membrane that has low methanol permeation and reactive chemical functionalities. Modification of these features makes PVA an attractive proton exchange membrane (PEM) alternative to Nafion^TM. However, the pristine PVA membrane is a poorer proton conductor than the Nafion^TM membrane due to the absence of negatively charged ions. Hence, modification of PVA matrixes whilst complying with the requirements of projected applications has been examined extensively. Generally, three modification methods of PVA membranes have been highlighted in previous reports, and these are (1) grafting copolymerization, (2) physical and chemical crosslinking, and (3) blending of polymers. The use of each modification method in different applications is reviewed in this study. Although the three modification methods can improve PVA membranes, the mixed method of modification provides another attractive approach. This review covers recent studies on PVA-based PEM in different fuel cell applications, including (1) proton-exchange membrane fuel cells and (2) direct-methanol fuel cells. The challenges involved in the use of PVA-based PEM are also presented, and several approaches are proposed for further study.

中文翻译：

---

聚（乙烯醇）基聚合物质子交换膜的发展及其在燃料电池应用中的挑战：综述

聚乙烯醇（PVA）是一种可生物降解的水溶性膜，具有较低的甲醇渗透性和反应性化学功能。这些功能的修改使PVA成为Nafion ^TM的一种有吸引力的质子交换膜（PEM）替代品。但是，原始的PVA膜比Nafion ^TM的质子导体差膜由于没有带负电的离子。因此，已经广泛地研究了在满足预期应用要求的同时对PVA基质进行改性的方法。通常，PVA膜的三种改性方法已在先前的报告中着重介绍，它们是（1）接枝共聚，（2）物理和化学交联以及（3）聚合物共混。在这项研究中综述了每种修改方法在不同应用中的使用。尽管三种改性方法可以改善PVA膜，但混合改性方法提供了另一种有吸引力的方法。这篇综述涵盖了在不同燃料电池应用中基于PVA的PEM的最新研究，包括（1）质子交换膜燃料电池和（2）直接甲醇燃料电池。