Alkaline membrane fuel cells: anion exchange membranes and fuels

Alkaline anion exchange membrane fuel cells (AAEMFC) are attracting ever-increasing attention, as they are promising electrochemical devices for energy production, presenting a viable opponent to the more researched proton exchange membrane fuel cells (PEMFCs). Consequently, great progress has been made in the area of designing and developing synthetic or naturally-derived anion exchange membrane (AEM), the properties of which have been discussed in this review, i.e. ionic conductivity, ion exchange capacity, fuel crossover, durability, stability and cell performance. Major groups of natural polymers (e.g. chitosan (CS)) and nanocellulose, together with modification/crosslinking routes, have been mentioned as more ecologically and economically viable raw materials for AEM processing compared to synthetic ones. Performances of fuel cells are also discussed, with different fuels used as anode feeds. Although the AEMFC technology is promising, the longevity challenges remain, originating from the still-limited long-term stability of hydroxide-conducting ionomers, particularly when operating at higher cell temperatures.