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Comparing B3LYP and B97 dispersion-corrected functionals for studying adsorption and vibrational spectra in nitrogen reduction
  • Esther Grossman,
  • Damilola DaramolaOrcid,
  • Gerardine Botte
Esther Grossman
Ohio University, Ohio University
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Damilola Daramola
Orcid
Ohio University
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Gerardine Botte
Texas Tech University
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Peer review status:UNDER REVIEW

11 May 2020Submitted to International Journal of Quantum Chemistry
12 May 2020Assigned to Editor
12 May 2020Submission Checks Completed
27 May 2020Reviewer(s) Assigned

Abstract

Electrochemical ammonia synthesis is being actively studied as a low temperature, low pressure alternative to the Haber-Bosch process. This work studied iridium as the electrochemical catalyst, following a previous study of adsorption characteristics on platinum. The characteristics studied include bond energies, bond lengths, spin densities, and free and adsorbed vibrational frequencies for the molecules N2, N, NH, NH2, and NH3. Overall, these descriptive characteristics explore the use of dispersion-corrected Density Functional Theory methods that can model N2 adsorption – the key reactant for electrochemical ammonia synthesis via transition metal catalysis. Specifically, three methods were tested: hybrid B3LYP, a dispersion-corrected form B3LYP-D3, and semi-empirical B97-D3. The latter semi-empirical method was explored to increase the accuracy obtained in vibrational analysis as well as reduce computational time. Two lattice surfaces, (111) and (100), were compared. The adsorption energies are stronger on (100) and follow the trend EB3LYP > EB3LYP-D3 > EB97-D3 on both surfaces.