Progress in the design and performance evaluation of catalysts for low-temperature direct ammonia fuel cells

Ammonia, a hydrogen-rich and carbon-free energy carrier, possesses advantages such as high energy density and convenient liquefaction storage and serves as an optimal medium for hydrogen storage. Low-temperature direct ammonia fuel cells (DAFCs) represent a highly promising pathway for the efficient utilization of ammonia energy. However, the sluggish kinetics of the low-temperature ammonia oxidation reaction (AOR), requires high loading of platinum-group metals (PGMs) catalysts, and their poisoning significantly hampers the performance of DAFCs, thereby limiting their large-scale commercial application. Therefore, it is crucial to design efficient, cost-effective, and stable catalysts. In this work, a detailed review of recent research efforts aimed at elucidating the mechanism underlying the AOR is presented. Building on this knowledge base, progress in the design and synthesis of both PGM and PGM-free catalysts for the AOR is discussed, as well as membrane electrode assembly (MEA) preparation processes for DAFCs. Furthermore, the results of the performance evaluation of AOR catalysts in single-cell tests are summarized. Finally, based on our findings from this research area thus far, potential design strategies for AOR catalysts that can promote the rapid development of low temperatures DAFCs are proposed.