Electrochemical ammonia oxidation reaction: From mechanistic understanding to practical applications

Electrochemical ammonia oxidation reaction (AOR) presents a promising avenue for realizing sustainable nitrogen cycling in various energy and environmental applications. However, sluggish catalytic activity, catalyst poisoning effects, and low stability pose significant challenges. Developing efficient electrocatalysts with high activity and stability necessitates a thorough understanding of the complex mechanisms and various reaction intermediates. In this review, we first discuss the AOR mechanism and the operando/in-situ characterization techniques employed for elucidating the reaction mechanisms. Subsequently, we summarize the development of AOR electrocatalysts, including noble-metal-based catalysts, non-noble-metal-based catalysts, and homogeneous catalysts. We also highlight the primary practical applications of AOR in energy, environment and chemical production fields, including direct ammonia fuel cells, chemical production of nitrates, nitrites, hydrogen, and wastewater treatment. Finally, based on the progress in electrochemical AOR, we discuss the challenges and propose future directions for advancing this field.