Degradation Mechanism of Membranes for Alkaline Membrane Fuel Cells

Hydroxide-conducting alkaline membranes have received growing attention for alkaline membrane fuel cells (AMFCs) and solid-state alkaline water electrolysis. The harsh operating conditions of the alkaline electrochemical devices require high chemical stability of the membranes. Cation (such as alkylammonium) functionalized polyaromatic membranes have been employed for the above electrochemical devices while such a cation is known to degrade chemically due to the high reactivity of hydroxide anion. Recently, we and other groups reported that the backbone part of polyaromatic membranes is also a site that can react with hydroxide anion, resulting in cleavage of the backbone part of membranes. Such degradation obviously deteriorates the performance of membranes to a large extent. In order to design more robust membranes which is stable under high pH conditions, it is necessary to understand the degradation mechanism at an atomistic level. Mechanistic aspects of the backbone degradation, however, have not been well understood, of which situation calls for contribution from theory. In this presentation, we report results of density functional theory calculations carried out to investigate the mechanism of backbone degradation of polyaromatic membranes.