Direct liquid fuel cells: A review

Direct liquid fuel cells (DLFCs) are one of the most promising types of fuel cells due to their high energy density, simple structure, small fuel cartridge, instant recharging, and ease of storage and transport. Alcohols such as methanol and ethanol were the most common types of fuel used, although glycols and acids are also used. The main problem that arose in direct liquid fuel cells (DLFCs) was the high cost of the catalyst and the high catalyst loading. Other issues, such as fuel crossover, cathode flooding, the generation of various side products, fuel safety and unproven long-term durability, must also be solved to improve the performance of DLFCs. More research studies were required to increase its performance and foster commercialization. Currently, there were some commercial products using direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs), but the other types of DLFCs were generally still in the research stage. This paper aims to review the different types of liquid fuels directly used in fuel cells and identify their properties, challenges and applications.