Copper-Based Catalyst Yields Unusual Ammonia Yield in Nitrate Electroreduction

Abstract

The electrochemical reduction of nitrate (NO3 -) ions into ammonia (NH3) provides an alternative method to produce highly valuable NH3 as well as eliminating harmful NO3 - pollutants. A variety of catalysts have been explored in recent times, however the NH3 production rate is far behind that of industrial Haber Bosch process which poses a major challenge for large scale synthesis. Herein, we have adopted an electrochemical synthetic route to produce highly porous copper nanoparticle enriched with (100) facets over copper foil containing which efficiently catalyzes NO3 - to NH3. Cu(100) rich electrocatalyst shows a significantly high NH3 production rate of greater than 1.0 mmol h-1 cm-2 even in the dilute NO3 - concentration of 14 mM, which is 4 to 5 times higher than the best reported values. Increasing the NO3 -concentration to 140 mM resulted in an NH3 production rate greater than 3.0 mmol h-1 cm-2, demonstrating that the catalyst is active in a wide range of NO3 - concentrations. Furthermore, durability test conducted in a flow system shows more than 100 h stability while maintaining a faradaic efficiency of greater than 98 %. Thus, we have successfully demonstrated the suitability of our catalyst at an industrially relevant scale.