Copper-Based Catalyst Yields Unusual Ammonia Yield in Nitrate Electroreduction

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. References: Patil, S. B.; Liu, T.-R.; Chou, H.-L.; Huang, Y.-B.; Chang, C.-C.; Chen, Y.-C.; Lin, Y.-S.; Li, H.; Lee, Y.-C.; Chang, Y. J., Electrocatalytic reduction of NO3 - to ultrapure ammonia on {200} facet dominant Cu nanodendrites with high conversion faradaic efficiency. The Journal of Physical Chemistry Letters 2021, 12 (33), 8121-8128. Hu, Q.; Qin, Y.; Wang, X.; Wang, Z.; Huang, X.; Zheng, H.; Gao, K.; Yang, H.; Zhang, P.; Shao, M., Reaction intermediate-mediated electrocatalyst synthesis favors specified facet and defect exposure for efficient nitrate–ammonia conversion. Energy & Environmental Science 2021, 14 (9), 4989-4997. He, W.; Zhang, J.; Dieckhöfer, S.; Varhade, S.; Brix, A. C.; Lielpetere, A.; Seisel, S.; Junqueira, J. R.; Schuhmann, W., Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia. Nature Communications 2022, 13 (1), 1129.