A room-temperature catalyst turns nitrate pollution into fertilizer feedstock

A copper-cobalt catalyst converts agricultural nitrate waste into green ammonia using renewable electricity, cleaning water while making fertilizer.

Researchers at Kochi University of Technology and Nagoya University have built a copper-cobalt oxide catalyst that converts nitrate pollution into ammonia using renewable electricity at ordinary temperature and pressure. The material is a heterostructure of crystalline copper oxide nanoparticles interfaced with amorphous cobalt oxide, made through a simple room-temperature chemical process. The work, led by Chunyu Yuan and colleagues, was published in Advanced Science.

The mechanism is the interesting part. During operation, copper reoxidizes and hydroxylates into hydroxyl-rich species that grab nitrate and hold intermediates in place, while the cobalt oxide splits water into hydrogen that migrates over to complete the reaction. The optimized catalyst reached an ammonia production rate of 54.68 mg per hour per milligram of catalyst, a Faradaic efficiency of 95.4 percent at -0.2 V versus RHE, and ran steadily for more than 60 hours in a flow cell. On simulated wastewater carrying 140 ppm nitrate, it cut the concentration to 7.45 ppm, well under the WHO drinking-water guideline of 50 ppm.

This matters for sustenance because it couples two problems into one solution. Today's ammonia comes from the Haber-Bosch process, which needs high heat and pressure and emits substantial CO2. Here, farm runoff that pollutes water becomes the raw material for cheap fertilizer, driven by clean electricity.

The caveats are real: testing used simulated wastewater, not the messier real thing, and long-term durability, scale-up, and renewable-power integration are all still listed as future work.

Source: Phys.org