Ammonia as a renewable energy carrier from synthesis to utilization

Ammonia has potential to play a key role in large-scale, long-term storage and transport of renewable energy. Renewable energy generation, particularly from solar and wind sources, has increased substantially but faces challenges such as intermittency and decentralization. Energy storage technologies are vital for addressing these issues, with chemical energy storage, especially ammonia, offering long-term (weeks) and large-scale (10–1,000 MW) energy storage. In this Review, we explore the role of ammonia in the energy landscape, focusing on its synthesis and utilization. Ammonia has advantages over hydrogen, such as higher volumetric energy density (12.7 MJ l−1) and simpler storage requirements (readily liquefied at ~10 bar or −33 °C). It can be synthesized using renewable electricity and later decomposed to release hydrogen or used directly in fuel cells, including direct-ammonia fuel cells, indirect-ammonia fuel cells and ammonia solid-oxide fuel cells. We show that although decentralized ammonia synthesis under mild conditions offers potential for localized, low-carbon production, it remains limited by high energy costs and scalability challenges, underscoring the need for breakthroughs in catalyst efficiency and system design. The successful integration of ammonia into renewable energy systems will require coordinated efforts across technology development, policy support and infrastructure expansion. Ammonia can store and transport renewable energy for large-scale and long-term use. This Review discusses its synthesis under mild conditions through metal-mediated electrochemical, direct plasma-catalytic and tandem plasma-electrocatalytic processes, along with economic considerations and utilization in hydrogen production and fuel cells.