Researchers at the Institute of Science Tokyo have developed a new antiperovskite-supported cobalt catalyst capable of producing ammonia from nitrogen and hydrogen under mild operational conditions without relying on precious metals. Reported in an experimental study published in the Journal of the American Chemical Society, this self-organizing nanostructured material unlocks a previously unknown cooperative mechanism between cobalt, barium, and aluminum. The catalytic system actively promotes nitrogen activation through the formation of molecular dinitrogen anions, designated as (N2)−. By leveraging this mechanism, the newly engineered catalyst successfully outperforms conventional benchmark ruthenium-based catalysts as well as traditional industrial iron catalysts. The achievement provides an alternative pathway for ammonia generation that avoids expensive and scarce noble metal resources while substantially reducing the energy requirements typically demanded by industrial chemical synthesis.

Ammonia remains best known globally for its indispensable role in agricultural fertilizer production, yet it is also rapidly attracting worldwide attention as a high-density, carbon-free hydrogen carrier. Despite this enormous technological promise, conventional ammonia synthesis continues to depend heavily on legacy industrial processes that operate under extreme high-temperature and high-pressure conditions.

To overcome this longstanding challenge, chemical scientists have dedicated substantial efforts toward creating advanced catalysts that can drive ammonia synthesis under substantially milder reaction conditions. Although several high-performance catalytic formulations have been successfully reported in recent years, they frequently depend on scarce and costly noble metals such as ruthenium. Barium-based materials have emerged as a potentially cost-effective alternative for lowering reaction thresholds; however, highly active compounds such as barium subnitride suffer from severe chemical instability in the presence of hydrogen gas and degrade rapidly during ongoing ammonia synthesis. Consequently, designing a robust and structurally stable barium-containing catalyst capable of activating diatomic nitrogen efficiently without rapid operational degradation has remained a formidable unresolved problem in contemporary catalyst development.

The research initiative to resolve this material challenge was led by Dr. Yihao Jiang, Professor Hideo Hosono, and Professor Masaaki Kitano from the MDX Research Center for Element Strategy at the Institute of Science Tokyo in Japan. Formed through the merger of Tokyo Medical and Dental University and Tokyo Institute of Technology, the research institution set out to synthesize a durable, multifunctional crystal matrix. The team successfully fabricated a new compound possessing the chemical formula Ba3AlO4–xNyHz, characterized by a flexible antiperovskite crystal structure. This distinct structural framework exhibits the unique ability to accommodate several distinct types of negatively charged chemical species simultaneously, including oxide, nitride, hydride, and molecular dinitrogen anions. Within this host matrix, nitrogen atoms exist in a highly activated state marked by a weakened nitrogen–nitrogen bond that makes subsequent chemical cleavage far easier to execute.

To maximize the practical catalytic efficiency of the material, the scientific team implemented a hierarchical nanostructuring approach during preparation. The researchers grew the newly synthesized Ba3AlO4–xNyHz material as an ultrathin protective and active shell directly onto the surface of aluminum oxide nanorods, substantially multiplying the overall accessible surface area available for gas interactions. Furthermore, the team incorporated cobalt into the composite, which self-organized during the synthesis process into discrete nanoclusters situated across the outer shell of the material.

When subjected to catalytic performance evaluations, the optimized cobalt-loaded composite demonstrated exceptional efficiency under remarkably gentle operating parameters. Testing revealed that the Co/Ba3AlO4–xNyHz/Al2O3 catalyst delivered an outstanding ammonia synthesis rate of 15.9 millimoles per gram of catalyst per hour under mild conditions of 300 degrees Celsius and a pressure of only 0.9 megapascals.

To uncover the precise fundamental mechanisms driving these elevated synthesis rates, the research team carried out a rigorous combination of isotope labeling experiments, advanced spectroscopic measurements, and detailed computer simulations. Their multi-technique investigation determined that molecular dinitrogen anions localized at the interface sites connecting cobalt, barium, and aluminum play the central role in catalyzing the reaction. Specifically, the barium-containing sites function to weaken the triple nitrogen–nitrogen bond, facilitating the rapid dissociation of the molecular dinitrogen anion while permitting quick replenishment from ambient nitrogen gas. Simultaneously, the adjacent cobalt and aluminum sites cooperate seamlessly to assist with the subsequent hydrogenation reaction steps that progressively convert the activated nitrogen intermediates into finished ammonia molecules.

The findings presented in the study establish a comprehensive design strategy for engineering robust, multi-element materials that incorporate activated nitrogen species to drastically enhance catalytic efficiency. These experimental insights offer actionable guidance for engineering next-generation ammonia production technologies that do not require expensive precious metals, directly supporting future low-carbon energy systems within an emerging hydrogen economy. As Kitano concluded, the work creates valuable new opportunities for developing highly active synthesis catalysts capable of operating efficiently and sustainably under mild chemical conditions.

Subject of Research: Low-temperature ammonia synthesis using an antiperovskite-supported cobalt catalyst

Article Title: Molecular dinitrogen anions pave the way for low-temperature ammonia synthesis

Article References: Molecular dinitrogen anions pave the way for low-temperature ammonia synthesis. Original publication (Bibliographic details unavailable.)

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Keywords: ammonia synthesis, antiperovskite catalyst, cobalt catalyst, molecular dinitrogen anions, Institute of Science Tokyo, hydrogen carrier, nitrogen activation, barium compounds, aluminum oxide nanorods, Journal of the American Chemical Society, clean fuel, mild reaction conditions, isotope labeling, spectroscopy, computer simulations, catalysis mechanisms, precious-metal-free catalysts