Ruthenium‐Doped Copper Nanowires for Nitrite/Nitrate to Ammonia Conversion and Their Integration in Zinc–Nitrite Batteries

Abstract The electrochemical reduction of nitrite (NO 2 − ) and nitrate (NO 3 − ) not only enables sustainable, circular routes to produce ammonia (NH 3 ), but also eliminates pollutants in groundwater. In this article, we report a facile synthesis of Ru‐doped Cu nanowires on Cu foam electrodes with low Ru (0.48 wt.%) loading. The composite electrode shows high‐performance in the NO 2 − /NO 3 − to NH 3 electroreduction, giving NH 3 Faradaic efficiency of up to 100% and NH 3 yield rates up to 33.2 mg h −1 cm −2 at −0.2 V versus RHE in NO 2 − reduction. For the nitrate‐to‐ammonia reduction, the electrode also shows high activity with Faradaic efficiency of 88.4% (at −0.6 V versus RHE) and a yield rate of 62.5 mg h −1 cm −2 (at −1.0 V versus RHE). We show that the electrode can easily be integrated into a Zn–nitrite battery, giving a power density of 9.1 mW cm −2 , a NH 3 yield rate of 1.88 mg h −1 cm −2 and a nitrite‐to‐ammonia Faradaic efficiency of 88.9% at a current density of 20 mA cm −2 . The system combines three productive outputs, that is removal of NO x − pollutants, synthesis of valuable NH 3 and generation of “green” electricity.