This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A new approach to producing ammonia using renewable electricity has overcome a fundamental energy limitation of the technology, opening new possibilities for cleaner and potentially more cost-effective production of one of the world's most important chemicals. Researchers from Monash University in Melbourne, Australia, have developed a new type of lithium-alloying electrode that significantly reduces the energy required to convert nitrogen gas into ammonia, a breakthrough that could help advance the transition away from fossil-fuel-based ammonia production.
Ammonia is essential to global agriculture, particularly as the basis of nitrogen fertilizers, and is increasingly being explored as a carbon-free fuel and energy carrier. However, conventional ammonia production relies on large, centralized facilities that cannot readily exploit geographically dispersed or stranded renewable energy. Published in Cell Press Blue, the research tackles one of the major obstacles facing electrochemical ammonia production: energy efficiency.
The most established electrochemical approach uses lithium to help activate nitrogen gas, an exceptionally stable molecule that is otherwise difficult to convert into ammonia. While the method can produce ammonia at practical rates, its chemistry imposes an intrinsic limit on how energy-efficient the process can become. The researchers, also working with colleagues at RMIT University, have now demonstrated that changing the chemistry of the cathode itself can overcome that limitation.
Rebecca Hodgetts, from the Monash University School of Chemistry, said the new cathode materials effectively changed the boundaries of what was thought possible. "Electrolytic synthesis of ammonia from renewables is possible, but present-day technology is fundamentally limited by low energy efficiencies and high costs," Hodgetts said. "Our new cathode materials change the rules of the game by redefining this fundamental limit and opening up previously unexplored opportunities for more energy- and cost-effective production of green ammonia." Instead of producing lithium metal on a conventional electrode, the researchers used gallium-based materials that combine with lithium.
This allows the lithium-mediated reaction to occur at substantially more favorable electrical potentials while retaining the ability to activate nitrogen and produce ammonia. Under optimized experimental conditions, the researchers achieved ammonia production with a faradaic efficiency of 96% ± 6%, meaning almost all the electrical current was directed toward producing ammonia. The research findings could support future electrochemical ammonia production with an estimated energy efficiency of at least 22%.
While further improvements are required to reach proposed commercial targets, the researchers say the study provides proof of concept that the longstanding energy barrier can be overcome through electrode design. Emeritus professor Douglas MacFarlane, also with the School of Chemistry, said the discovery also expands the chemistry available to researchers working on renewable ammonia production. "The field has essentially been limited to a single cathode process based on lithium-mediated nitrogen reduction," MacFarlane said.
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