(639b) Electrochemical Nitrogen Reduction Reaction: Quasi-Reference Electrodes for Improved Parameter Control

The electrochemical reduction of nitrogen has received a significant amount of attention in recent years as many researchers seek to find more sustainable methods for producing ammonia to meet a growing global demand. The competing hydrogen evolution reaction (HER) remains the most significant obstacle to an efficient reaction, and much research has been devoted to finding more efficient catalysts for the nitrogen reduction reaction (NRR) [1].

One major issue confronting researchers investigating the electrochemical NRR is the lack of consistent experimental procedures. Different catalysts, materials and loadings can make results in different research articles difficult to accurately compare. Many works utilize fuel cell type setups, as well as gas phase reactions at the working electrode [2-5]; however, this has a significant drawback in that traditional reference electrodes cannot be used. Without a reference electrode the potential of the cathode cannot be accurately measured, and as a result this makes experimental comparisons challenging. To that end, a novel approach using a quasi-reference electrode has been investigated in order to develop a methodology to more accurately investigate and compare different electrocatalysts for the NRR. The ability to identify the potential of the cathode in an electrochemical NRR cell is critical due to the fact that at high overpotentials the dominance of the HER is believed to be even greater; for this reason, the overpotential used for various electrocatalysts is an important parameter to quantify for the electrochemical NRR. In this work, the importance of such standard methodologies as well as other important techniques such as the use of controls is demonstrated in order to contribute to the growing discussion regarding the challenges facing the electrochemical production of ammonia.

[1] X. Y. Cui, C. Tang, and Q. Zhang, "A Review of Electrocatalytic Reduction of Dinitrogen to Ammonia under Ambient Conditions,", Advanced Energy Materials, Review vol. 8, no. 22, p. 25, Aug 2018, Art no. 1800369, doi: 10.1002/aenm.201800369.

[2] J. N. Renner, L. F. Greenlee, A. M. Herring, and K. E. Ayers, "Electrochemical Synthesis of Ammonia: A Low Pressure, Low Temperature Approach,", Electrochemical Society Interface, Article vol. 24, no. 2, pp. 51-57, Sum 2015.

[3] J. H. Park et al., "Anion-exchange-membrane-based electrochemical synthesis of ammonia as a carrier of hydrogen energy,", Korean Journal of Chemical Engineering, Article vol. 35, no. 8, pp. 1620-1625, Aug 2018, doi: 10.1007/s11814-018-0071-3.

[4] X. Y. Cui, C. Tang, X. M. Liu, C. Wang, W. J. Ma, and Q. Zhang, "Highly Selective Electrochemical Reduction of Dinitrogen to Ammonia at Ambient Temperature and Pressure over Iron Oxide Catalysts,", Chemistry-a European Journal, Article vol. 24, no. 69, pp. 18494-18501, Dec 2018, doi: 10.1002/chem.201800535.

[5] R. Lan, J. T. S. Irvine, and S. W. Tao, "Synthesis of ammonia directly from air and water at ambient temperature and pressure,", Scientific Reports, Article vol. 3, p. 7, Jan 2013, Art no. 1145, doi: 10.1038/srep01145.