Direct ammonia solid oxide fuel cells: a comprehensive review of principles, materials, and recent advances

The global ambition to achieve net-zero emissions by 2050 is driving intense research into low-carbon energy vectors to mitigate the climate impact of the dominant use of fossil fuels. This challenge creates significant demand for sustainable energy sources to support the transition. While hydrogen is a key component of the green energy economy, ammonia has emerged as a highly promising alternative. Its distinctive qualities as a carbon-free fuel and an efficient hydrogen carrier offer a viable pathway to reduce emissions. Ammonia can both complement existing energy infrastructure (such as natural gas or grey/blue hydrogen) to accelerate near-term decarbonization and ultimately serve as a mainstream renewable energy vector in a fully net-zero economy. This review details the potential of ammonia as a renewable energy carrier, its storage, production, and distribution. It encompasses technologies such as the traditional Haber-Bosch process and new ammonia production methods, including electrochemical synthesis, and focuses on their efficiency, scalability, and environmental impact. The recent advances, principles, and challenges of direct ammonia fuel cells are discussed, with a focus on different cell mechanisms, electrolyte materials, and catalysts. The review also discusses applications of ammonia-based solid electrolyte fuel cells across sectors, highlighting their flexibility and economic potential as critical decarbonization technologies.