Unlocking the potential of ammonia for hydrogen production: A review of electrocatalytic ammonia oxidation reaction

With the impending catastrophic impact of climate change and global warming due to greenhouse gas emissions from fossil fuel use and the growing global energy demand, the world stands at a critical crossroads in the search for and development of alternative energy sources. Ammonia, widely used as a hydrogen carrier, offers a practical means to store and transport hydrogen efficiently. The electrochemical decomposition of ammonia into hydrogen presents a promising pathway to unlock its potential as a sustainable energy resource, enabling cleaner energy production while mitigating storage and transportation challenges. However, the industrial application of this process is hindered by the need for robust, highly active catalysts, and advanced reactor configurations, mainly involved in ammonia oxidation reaction (AOR). This review begins with an in-depth discussion of the fundamentals of AOR, including electrocatalyst history and catalyst development, focusing on active components, promoters, support materials, and synthesis strategies. Various metal-based catalysts, from non-noble to noble metals, are rigorously assessed for their potential in electrocatalytic AOR. The side and competing reactions involved in AOR are discussed, while the application of Density Functional Theory (DFT) is explored to provide insights into the atomistic simulation of catalyst surfaces and electrochemical reactions. Additionally, the review examines factors that influence electrocatalyst activity, identifying both challenges and opportunities for improvement. Overall, this work presents new perspectives and future research directions to address current challenges and advance the development of highly effective catalysts, thereby driving the process toward industrial application.