Recent progress in Pt-based electrocatalysts for ammonia oxidation reaction

Abstract

Ammonia oxidation reaction (AOR) has attracted great interest in the context of electrocatalytic hydrogen generation and direct fuel generation. Owing to its low theoretical cell voltage, the ammonia oxidation electrode is considered a promising anode candidate for electrical energy conversion systems. However, its low kinetics causes a high overpotential and results in a loss of cell efficiency. Pt is well known as the best AOR catalyst, and Pt-based catalysts have been mainly studied. Pt-free catalysts have also been reported, but they exhibit insufficient performance compared to Pt-based catalysts. In this review, we briefly discuss the advantages of ammonia fuel and its promising applications in energy-conversion systems. Although the AOR mechanism remains controversial, most experimental studies and theoretical calculations have been conducted on Pt catalysts. We highlight recent progress in electrical ammonia oxidation electrodes based on the fundamentals of the AOR mechanism. In particular, we focus on designing a strategy for achieving high AOR activity and its application to ammonia electrolysis cells and direct ammonia fuel cells. Finally, prospective directions for the study of AOR catalysts and practical devices were discussed. © 2022 Elsevier Ltd