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

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 N-N, N-O, or N-H bonds. Moreover, it can be used as the anode reaction in ammonia electrolyzers for H-2 production or in ammonia fuel cells. We study here the reaction on the N-2-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 N-2 is formed via an *NH + *NH coupling step, in accordance with the Gerischer-Mauerer mechanism. Other N-N bond forming steps are considered less likely based on either their unfavourable energetics or the low coverage of the necessary monomers. The N N coupling is inhibited by strongly adsorbed *N and *NO species, which are formed by further oxidation of *NH. (C) 2018 Elsevier Inc. All rights reserved.