Review — Ammonia oxidation electrocatalysis for hydrogen generation and fuel cells

Multitude of complications involved with handling hydrogen fuels has propelled many to consider instead an ammonia economy. Ammonia electrooxidation reaction (AOR) herein is discussed as a means for energy application either by electrochemical decomposition for onsite hydrogen generation or by direct employment of ammonia as a fuel in a direct ammonia fuel cell. The development of a robust and stable AOR catalysts are pivotal for both applications, alongside the development of a high-performing HER and ORR catalysts. Examined here are the different operating conditions for both applications and different hurdles to overcome for the catalyst development. The kinetics and mechanism of ammonia electrooxidation are elucidated to provide a foundation to better understand the issues associated with this technology and a comprehensive review on Pt-free catalysts that have been explored for AOR is presented in order to facilitate future research direction in this promising technology.