Electrocatalyst design strategies towards high performance anion-exchange membrane-based direct ammonia fuel cells

Abstract

Direct ammonia fuel cells (DAFCs) with anion-exchange membranes (AEMs) are considered a valuable contributor to a carbon-neutral clean energy society, benefitting from the existence of long-established ammonia infrastructure. However, the relatively low cell performance of DAFCs compared to the hydrogen-based fuel cells and the critical issues related to catalyst poisoning limit the widespread use of DAFCs and have spurred multi-directional efforts to develop tailored catalyst compositions and structures specific to DAFCs. In this review, we outline recent progress in the development of electrocatalysts for DAFCs. First, we summarize the operating principles of DAFCs and address critical challenges in electrode reactions, the ammonia oxidation reaction (AOR) and oxygen reduction reaction (ORR). Subsequently, we present an overview of recent endeavours to enhance activity, selectivity, and durability of catalysts for each electrode reaction. We categorize the electrocatalytic exemplars into platinum group metal (PGM) and non-PGM compositions and provide systematic comparisons of each strategy to provide a more comprehensive understanding of catalyst design. Lastly, this review highlights remaining challenges and offers insights into future directions for optimizing DAFC performance.