AI Article Synopsis

  • There is limited understanding of how ammonia decomposes on TiO and the influence of water on this process.
  • Using First-Principles Molecular Dynamics (FPMD) and Density Functional Theory (DFT) calculations, researchers found that pure ammonia leads to surface changes that hinder proton transfer, complicating the decomposition reaction.
  • Introducing water alters the hydrogen bonding environment, resulting in increased positive charge on H atoms and shorter hydrogen bond distances, which lowers activation energy barriers and changes hydroxyl coverage on TiO surfaces.
  • This study enhances knowledge about water's effect on ammonia decomposition, paving the way for better reaction optimization.

Article Abstract

There is still a paucity of fundamental understanding about the reaction of ammonia decomposition over TiO, especially the role of water. Herein, FPMD and DFT calculations were used to address this concern. The results reveal that ammonia decomposition in pure ammonia causes the hydroxylation of the surfaces and reduction of the proton acceptor sites, making proton transfer (PT) difficult, increasing the distances between the NH and O sites and changing the adsorption configurations of NH, which are not favourable for accepting protons from NH dissociation. When water is introduced, the local hydrogen bonding environment, consisting of NH and HO with the HO dynamically close to the OH, promotes the increase of the positive charge of H atoms from 0.133 to 1.47 e, which increases the OH bond dipole moment from 1.136 to 1.400 Debye, resulting in the shortening of the H-bond distances between NH and OH (1.858 1.945 Å of only NH) and enlarging the OH bonds (0.980 1.120 Å). This reduces the activation energy barriers of OH deprotonation and causes the surfaces to have low hydroxyl coverage from 0.425 to 0.382 eV. Our study reveals the role of water and provides new insights into ammonia decomposition on TiO.

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Source
http://dx.doi.org/10.1039/d3cp06328cDOI Listing

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