Measuring and predicting accurate spectroscopic signatures of catalytic systems is essential to monitor and validate reaction mechanisms to provide a basis for rational catalyst design. Here, we to predict the binding and vibrational features of adsorbate species (H, N, NH2, NH3, and N-2) important for ammonia synthesis on pure and doped Fe-bcc(111), Fe-bcc(211), and reconstructed (Fe-bcc(211)R) surfaces. We focus on configurations predicted to be dominant under realistic reaction conditions. For each configuration, the vibrational modes with expected high IR intensity (motions perpendicular to the surface or signature modes of complex species such as NH2 or NH3) are singled out and discussed in terms of the following: (a) a comparison with previous experiments to validate the accuracy of our results, and (b) a perspective use in operando/in situ monitoring of catalytic processes. We find that calculated frequencies and intensities are in good agreement with available experimental data, thus, validating our predictions. We then show that changes in the frequencies of characteristic modes as a function of doping and reaction conditions (giving different dominant configurations) could be observable via vibrational spectroscopy. Monitoring these signatures could enable determination of the catalytically active configurations in the complex catalytic process as well as the surface orientations most influential on reaction rates. This could allow unambiguous identification of reaction mechanisms.
Vibrational Spectroscopy Signatures of Catalytically Relevant Configurations for N-2 Reduction to NH3 on Fe Surfaces via Density Functional Theory
Fortunelli Alessandro;
2021
Abstract
Measuring and predicting accurate spectroscopic signatures of catalytic systems is essential to monitor and validate reaction mechanisms to provide a basis for rational catalyst design. Here, we to predict the binding and vibrational features of adsorbate species (H, N, NH2, NH3, and N-2) important for ammonia synthesis on pure and doped Fe-bcc(111), Fe-bcc(211), and reconstructed (Fe-bcc(211)R) surfaces. We focus on configurations predicted to be dominant under realistic reaction conditions. For each configuration, the vibrational modes with expected high IR intensity (motions perpendicular to the surface or signature modes of complex species such as NH2 or NH3) are singled out and discussed in terms of the following: (a) a comparison with previous experiments to validate the accuracy of our results, and (b) a perspective use in operando/in situ monitoring of catalytic processes. We find that calculated frequencies and intensities are in good agreement with available experimental data, thus, validating our predictions. We then show that changes in the frequencies of characteristic modes as a function of doping and reaction conditions (giving different dominant configurations) could be observable via vibrational spectroscopy. Monitoring these signatures could enable determination of the catalytically active configurations in the complex catalytic process as well as the surface orientations most influential on reaction rates. This could allow unambiguous identification of reaction mechanisms.File | Dimensione | Formato | |
---|---|---|---|
prod_462033-doc_180344.pdf
solo utenti autorizzati
Descrizione: published article
Tipologia:
Versione Editoriale (PDF)
Licenza:
NON PUBBLICO - Accesso privato/ristretto
Dimensione
4.58 MB
Formato
Adobe PDF
|
4.58 MB | Adobe PDF | Visualizza/Apri Richiedi una copia |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.