(Invited) U.S. DOE Early-Stage Alkaline Membrane Fuel Cell R&D

Abstract

The U.S. Department of Energy (DOE) supports research, development, and demonstration of fuel cell technologies for transportation, stationary, and early market applications. Fuel cell research and development (R&D) efforts predominantly concentrate on R&D of fuel cell stack materials and components to achieve low-cost, high performance fuel cell systems, and include longer term technologies, such as alkaline membrane fuel cells (AMFCs). More favorable oxygen reduction kinetics and increased platinum group metal (PGM)-free catalyst stability at high pH conditions have invigorated interest in alkaline membrane fuel cells as an alternative to polymer electrolyte membrane fuel cells (PEMFCs), on which fuel cell electric vehicles currently available for retail sale are based. The catalyst accounts for >40% of the projected high-volume stack cost in PEMFC electric vehicles, owing largely to the inclusion of PGMs [1]. Achieving cost competitiveness with internal combustion engine vehicles will be expedited by eliminating PGM-based catalysts; AMFCs offer a promising route for successfully incorporating state of the art PGM-free catalysts into membrane electrode assemblies (MEAs). Alkaline membrane R&D is targeted to increase the operating temperature and humidity ranges of fuel cells while improving conductivity and to increase membrane mechanical, chemical, and thermal stability with diminished fuel crossover. In 2016, an expert-led workshop on alkaline electrolyte membranes (AEMs) was convened by the DOE based on intense interest in the field and recent advances including performance of >1 W/cm2 in H2/O2 MEA testing [2]. There was consensus on the need for AEM-specific standardized protocols and testing and for further improvement in MEA performance. In order to accelerate materials development within the field, the DOE has set an AMFC-specific 2020 technical milestone of PGM-free MEA demonstration of >600 mW/cm2 performance in H2/air. Stable, conductive polymer materials and durable hydrogen oxidation catalysts are key to realizing commercially relevant AEMFCs. Existing efforts in the DOE R&D portfolio include increasing performance and durability in perfluorinated and hydrocarbon-based ionomers, increasing cation group stability, diminishing catalyst deactivation due to ionomer-catalyst interaction, and PGM-free MEA performance of 350 mW/cm2. Going forward, the profound lack of readily available, stable AEMs or ionomers for high pH MEAs must be addressed in order to expand entry into the field and foster more rapid progress in AEMFC development.