(Invited) Fuel Cells Fueled By Sustainable Liquid Fuels

Abstract

The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical technologies for energy transformation and storage for distributed, grid scale and automotive applications. Recently hydrogen PEM fuel cells (FC) made great progress in performance, durability and cost that reflected in the emerging of multiple commercial vehicles powered by FCs. However their market penetration is hampered mostly by the absence of hydrogen infrastructure including transportation and storage, and high cost of its implementation. On the other side, carbon-neutral liquid fuels (CNLFs) have energy density higher than of liquid hydrogen, better safety, low footprint and cost of transportation and storage. Easily liquefied ammonia and dimethyl ether as well as more traditional lower alcohols are the most promising CNLFs. They can be used with or without internal reforming in direct liquid fuel cells (DLFCs) or as a hydrogen carrier for PEM fuel cells thus allowing the use of existing liquid fuels infrastructure. History of DLFCs started in 1960s from first GE attempts to use diesel fuel in a FC and continued with development of direct methanol fuel cells (DMFCs). In spite intensive research, the latter found very limited application because of low efficiency and power density. As conventional low temperature PEMs and AEMs content a lot of water to support high H+ or OH- conductivity, high crossover rate of most CNLFs is inevitable and leads to low cell voltage and energy efficiency. In addition, traditional platinum group metal catalysts are easily poisoned by CNLFs or by intermediate oxidation products. Therefore, to realize high energy density of CNLFs and provide high FC power density, it is necessary to increase operation temperature of DLFCs, develop more active and less expensive electrocatalysts, develop selective ion conducting membranes and design electrodes and cells for using liquid fuels. Recent advances in the development of novel DLFCs that is being funded by ARPA-E via REFUEL and OPEN 2018 programs will be presented. Possible future ARPA-E program targeting the use of such fuel cells for transportation (in hybrids, range extenders, APUs for aviation and ground transportation) will be also discussed.