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

Scientists have developed a novel catalyst for ammonia synthesis that operates efficiently at relatively low temperatures and pressures, potentially reducing costs and environmental impact. Ammonia (NH₃) is commonly used in fertilizer production, but its synthesis typically requires high temperatures and pressures, making it unsustainable for large-scale applications.

In their study published in the Journal of the American Chemical Society, researchers led by Dr. Yihao Jiang from the MDX Research Center for Element Strategy at Science Tokyo introduce a hierarchically structured antiperovskite-supported cobalt catalyst. This catalyst is supported on a barium-based antiperovskite shell, which incorporates molecular dinitrogen anions (N₂)⁻.

These negatively charged nitrogen species enable efficient nitrogen activation by weakening the nitrogen–nitrogen bond, making it easier to break and synthesize ammonia. The researchers achieved remarkable results, with the optimized catalyst demonstrating ammonia synthesis rates of 15.9 mmol per gram of catalyst per hour under mild conditions of 300 °C and 0.9 MPa.

This rate outperforms existing ruthenium-based and industrial iron catalysts, suggesting the potential for more sustainable and cost-effective ammonia production. The study also uncovered a previously unknown mechanism where activated N₂⁻ ions at the interface between cobalt, barium, and aluminum facilitate the ammonia synthesis process.

This discovery could pave the way for the development of new, highly active ammonia production technologies that rely less on precious metals, contributing to the emergence of a low-carbon hydrogen economy.