Hydrogen peroxide fuel cell membrane stability

To compare different polymers with respect to their chemical stability, the Fenton test is widely applied in fuel cell membrane research. In these tests, membrane samples are immersed in hydrogen peroxide solution containing a small amount of Fe " ", e.g., iron(lI)sulfate. In the presence of the metal ion, the decomposition of hydrogen peroxide is accelerated. The ongoing reactions are very complex, and several reactive intermediates are formed. Just as an example and demonstrating the catalytic nature, the following partial reactions of the so-called Haber-Weiss mechanism are highlighted, as shown in (6.28)-(6.31) [49, 50]. 

Hydrogen peroxide decomposition catalysts can be added to ionomer membranes in small amounts to slow down the decomposition of the ionomer during fuel cell operation. Additions of cerium and manganese, in both oxide and ionic forms, have been shown to increase the oxidative stability of membranes by orders of magnitude, and fuel cells prepared with such membranes have shown substantial increases in hfetime under aggressive hot and dry operation [60-62]. Unfortunately, these metal ions and oxides can consume ion exchange capacity and negatively impact fuel cell performance. 

Abstract Sulfonated polyimides have been designed to be used as proton conducting membranes in fuel cells. These materials present most of the required properties for this application, including a high level of ionic conductivity, a low gas and methanol permeability, and good mechanical properties. However, they exhibit a low stability when immersed in liquid water and in hydrogen peroxide solutions at elevated temperature due to a high sensitivity of the imide functions to hydrolysis. The aim of this article is to review the different routes of synthesis, the membrane-specific properties, the structural and transport property characteristics, and finally their behavior in fuel cells in terms of performance and stability. 

---