Alkaline fuel cells: Status and prospects

Abstract

Alkaline fuel cells (AFC) have proven to provide high power densities and can attain considerable lifetimes, thus making them a worthy competitor to proton exchange membrane fuel cells (PEMFC). The electrolytes are based on aqueous bases and are relatively inexpensive. The non-corrosive nature of their electrolyte facilitates diverse usage of various catalyst materials apart from platinum, thus enabling the mass production of low-cost fuel cells. This review provides a summarized overview of AFCs. It sheds light on its fundamental operational principles, the most recent research trends related to catalyst developments, its system components and stack designs, and also provides a brief performance analysis section that highlights how the performance of an AFC is impacted upon varying different system parameters (e.g. electrolyte concentration, electrolyte thickness, and operating temperatures). This parametric study has shown that increasing the electrolyte concentration from 1–61 mol/L results in an increase in the AFC’s peak power density from 72.9 to 169 W/m2. Similarly, increasing the cell’s operating temperatures from 243–283 K yields increased peak power densities from 112 to 140 W/m2. This is mainly attributed to the enhancement of the electrolyte’s specific conductivity and the cell’s overall electrochemical kinetics. Increasing the electrolyte thickness, however, decreases the performance of an AFC, where peak power densities fall from 123 to 66 W/m2 when the thickness increases from 1 to 5 μm. This is a consequence of the increased internal resistances encountered by the hydroxyl ions as they migrate through the electrolyte.

Keywords

• Alkaline fuel cell
• HOR catalysts
• ORR catalysts
• Modeling
• Electrode design