On the mechanism of the electrochemical conversion of ammonia to dinitrogen on Pt(100) in alkaline environment

Katsounaros, I.; Costa, Figueiredo, M.; Calle Vallejo, F.; Li, H.; Gewirth, A.A.; Markovic, N.M.; Koper, M.T.M. (2018)

Article / Letter to editor

The electrochemical oxidation of ammonia to dinitrogen is a model reaction for the electrocatalysis of the nitrogen cycle, as it can contribute to the understanding of the making/breaking of NN, NO, or NH bonds. Moreover, it can be used as the anode reaction in ammonia electrolyzers for H₂ production or in ammonia fuel cells. We study here the reaction on the N₂-forming Pt(1 0 0) electrode using a combination of electrochemical methods, product characterization and computational methods, and suggest a mechanism that is compatible with the experimental and theoretical findings. We propose that N₂ is formed via an ^∗NH + ^∗NH coupling step, in accordance with the Gerischer-Mauerer mechanism. Other NN bond-forming steps are considered less likely based on either their unfavourable energetics or the low coverage of the necessary monomers. The NN coupling is inhibited by strongly adsorbed ^∗N and ^∗NO species, which are formed by further oxidation of ^∗NH.

• Single-crystal electrochemistry
• Electrocatalysis
• Physical electrochemistry
• Nitrogen cycle
• Ammonia oxidation

• All authors: Katsounaros, I.; Costa, Figueiredo, M.; Calle Vallejo, F.; Li, H.; Gewirth, A.A.; Markovic, N.M.; Koper, M.T.M.
• Date: 2018-03-31
• Journal: Journal of Catalysis
• Volume: 359
• Pages: 82 - 91
• DOI: doi:10.1016/j.jcat.2017.12.028