Electrocatalytic Ammonia Oxidation Reaction: Selective Formation of Nitrite and Nitrate as Value-Added Products.

Abstract

Ammonia (NH₃) plays a pivotal role as a hydrogen carrier, offering a carbon-free energy alternative for sustainable energy systems. The ammonia electrooxidation reaction (AmOR) emerges as a promising avenue to leverage NH₃ in energy conversion and environmental applications. This review explores the multifaceted importance of NH₃ oxidation through three primary strategies: its integration into fuel cell technology for clean energy generation, its use in wastewater treatment for ammonia removal, and its application in electrolyzer setups for producing value-added products. Special emphasis is placed on oxidizing NH₃ to nitrite (NO₂ ^-) and nitrate (NO₃ ^-) in electrolyzers as a potential alternative to the energy-intensive Ostwald process. The review highlights recent advances in catalyst development for efficient NO₂ ^-/NO₃ ^- synthesis, the influence of the pH on reaction selectivity, and various reported experimental AmOR solutions. By addressing these critical aspects, this work aims to underscore the potential of NH₃ oxidation in electrolyzers for sustainable energy solutions. Potential future research directions and challenges are also discussed.