(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 crosscutting applications. Applied, early-stage fuel cell research and development (R&D) efforts predominantly focus on 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 could 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). In addition, improved alkaline exchange membranes (AEMs) have crosscut benefits to applications beyond fuel cells, including electrolysis for hydrogen production and reversible fuel cells. Alkaline membrane R&D is targeted to increase conductivity over a wider range of operating temperature and relative humidity and to increase membrane mechanical, chemical, and thermal stability with diminished fuel crossover. In 2016, an expert-led workshop on AEMs was convened by the DOE based on intense interest in the field [2]. There was consensus on the need for AEM-specific standardized protocols and testing and for further improvement in MEA performance. Furthermore, 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 AMFC development. In order to increase coordination in the polymer electrolyte membrane community (including AEMs) to accelerate R&D success in fuel cells and other devices (electrolyzers, redox flow batteries, etc.), the FCTO has recently organized the National Laboratory-led Membranes Working Group. Stable, conductive polymer materials and durable hydrogen oxidation catalysts are key to realizing commercially relevant AMFCs. This presentation will highlight recent advancements in AMFCs 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. This presentation will also provide an outlook on future activities.