The ammonia oxidation reaction (AOR) is an electrochemical reaction that produces hydrogen and nitrogen gas from ammonia. Due to the relevance of hydrogen gas in the implementation of green energy, optimizing the catalysis of this reaction is essential for the application of the AOR [1]. The density functional theory (DFT) models commonly used to study this reaction are often vacuum based, and can lack accuracy in comparison to solvated models [2]. This project will use an explicit solvent model to accurately represent the water-metal interaction, along with the computational hydrogen electrode to observe the effects of this reaction system on the thermodynamics of the AOR. The system will be modelled on iridium, platinum, palladium, and ruthenium surfaces, which allows for direct comparison to our previously published vacuum-only AOR study [3]. A number of different overlayer configurations and molecular orientations are investigated to ensure an accurate picture of the water-metal interaction is established. We investigate two different solvation models: one in which the water hexamer is kept intact with the adsorbate added in (the add. model), and one with the water hexamer interrupted by inserting the adsorbate into the hexamer, replacing one of the water molecules (the rep. model). Our results thus far indicate that the add. model tends to result in a water structure more displaced from the surface, whereas the rep. model experiences disruptions of the perfect hexagonal lattice to form new tessellation patterns. In addition, the water molecules arranged in a predominantly H-up pattern tends to increase the work function compared to a predominantly H-down pattern, consistent with previous studies [4]. The overall effect of solvation on the reaction pathway is a tendency to decrease the limiting potential for Pt and Ru. These results highlight the importance of incorporating solvent effects into DFT models of electrochemical reactions.

1. Vitse, F., Cooper, M. & Botte, G. G. On the use of ammonia electrolysis for hydrogen production. J Power Sources 142, 18–26 (2005).
2. Zhang, Y., Xiong, Y., Wang, Y., Wang, Q. & Fan, J. Advances in computational approaches for bridging theory and experiments in electrocatalyst design. Nanoscale Horizons vol. 10 2211–2238 Preprint at https://doi.org/10.1039/d5nh00216h (2025).
3. Laframboise, B. J. R., Coveny, J., Zhou, J. & Chen, L. D. Computational Design of Pt-M (M = Au, Ir, Pd, Rh, and Ru) Binary Alloys for Enhanced Ammonia Oxidation Electrocatalysis. ChemElectroChem 12, (2025).
4. Groß, A. & Sakong, S. Ab Initio Simulations of Water/Metal Interfaces. Chemical Reviews vol. 122 10746–10776 Preprint at https://doi.org/10.1021/acs.chemrev.1c00679 (2022).