Scientists at Tokyo Metropolitan University have revealed how copper oxide catalysts transform during reactions to dramatically increase ammonia yields. This breakthrough in electrochemical nitrate reduction could lead to cleaner alternatives to the energy-intensive Haber-Bosch process. The findings highlight a key metallic copper formation that enhances efficiency at ambient conditions.
Ammonia, essential for fertilizers and global agriculture, is traditionally produced via the Haber-Bosch process, which requires high temperatures and pressures, consuming vast energy and contributing about 1.4% of worldwide carbon dioxide emissions. Seeking sustainable options, a team led by Professor Fumiaki Amano at Tokyo Metropolitan University explored the electrochemical nitrate reduction reaction, which generates ammonia from nitrates at room temperature and normal atmospheric pressure.
Using advanced operando X-ray absorption techniques, the researchers attached copper oxide particles to carbon fibers and applied varying voltages to an electrolyte solution. Initially, under positive voltage, nitrate ions bind to the catalyst surface, passivating it and promoting nitrite ion formation while preventing conversion to metallic copper. As voltage shifts more negative, metallic copper particles emerge, marked by increased copper-copper bonds, coinciding with a sharp rise in ammonia production.
This metallic copper facilitates hydrogen addition to nitrite ions, driving the reaction toward ammonia. The study demonstrates that surface passivation and in-situ copper formation are crucial for catalyst performance in this process. Published in ChemSusChem in 2025, the work by Rizki Marcony Surya, Surya Pratap Singh, Kosuke Beppu, and Fumiaki Amano (DOI: 10.1002/cssc.202501785) suggests strategies for designing more efficient electrochemical catalysts, potentially reducing the environmental footprint of ammonia synthesis and supporting greener industrial chemistry.