Rational design of electrocatalytic system to selective transform nitrate to nitrogen

Nitrate (NO₃^-) is one of the most common pollutants in natural bodies of water and as such threatens both human health and the safety of aquatic environment. There are efficient electrochemical techniques to directly remove NO₃^-, but inexpensive, selective and electrocatalytic strategies to eliminate NO₃^- by converting it into benign nitrogen (N₂) remain challenging. This work studied Cu particles that were formed directly on a Ni foam (Cu-NF) and evaluated their electrocatalytic NO₃^- reduction performance. The use of carbon nanotubes (CNT) functionalized with titanium suboxides (TiSO) as the anode facilitated the generation of active chlorine species that had a key role in the removal of NH₄⁺. An electrochemical system that integrated a Cu-NF cathode with a TiSO-CNT anode could remove 88.5% of NO₃^- with a >99% N₂ selectivity when operated over 6 h (4.1 × 10^-4 h^-1) at a potential of -1.2 V vs Ag/AgCl. Because the chloride ions are very common in natural sources of water, this technique offers a sustainable and environmentally friendly approach for the removal of NO₃^- from contaminated water sources.