Stability Changes in Iridium Nanoclusters via Monoxide Adsorption: A DFT Study within the van der Waals Corrections

Autor(es)

Yonezawa, Alex F. ^[1] ; Nagurniak, Glaucio R. ^[2] ; Orenha, Renato P. ^[3] ; da Silva, Eder H. ^[3] ; Parreira, Renato L. T. ^[3] ; Piotrowski, Mauricio J. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Pelotas, Dept Phys, BR-96010900 Pelotas, RS - Brazil

^[2] Univ Fed Santa Catarina, Dept Exact Sci & Educ, BR-89036004 Blumenau, SC - Brazil

^[3] Univ Franca, Nucleo Pesquisas Ciencias Exatas & Tecnol, BR-14404600 Franca, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry A; v. 125, n. 22, p. 4805-4818, JUN 10 2021.
• Citações Web of Science: 0

Resumo

Small iridium nanoclusters are prominent subnanometric systems for catalysis-related applications, mainly because of a large surface-to-volume ratio, noncoalescence feature, and tunable properties, which are completely influenced by the number of atoms, geometry, and molecular interaction with the chemical environment. Herein, we investigate the interaction between Ir-n nanoclusters (n = 2-7) and polluting molecules, CO, NO, and SO, using van der Waals D3 corrected density functional theory calculations. Starting from a representative structural set, we determine the growth pattern of the lowest energy unprotected Ir-n nanoclusters, which is based on open structural motifs, and from the adsorption of a XO (X = C, N, and S) molecule, the preferred high-symmetric adsorption sites were determined, dominated by the onefold top site. For protected systems, 4XO/Ir-4 and 6XO/Ir-6, we found a reduction in the total magnetic moment, while the equilibrium bonds of the nanoclusters expanded (contracted) due to mCO and mNO (mSO) adsorption, with exceptions for systems with large structural distortions (4SO/Ir-4 and 6NO/Ir-6). Meanwhile, the C-O and N-O (S-O) bond strength decreases (increases) following an increase (decrease) in the C-O and N-O (S-O) distances upon adsorption. We show, through energetic analysis, that for the different chemical environments, relative stability changes occur from the most stable unprotected nanoclusters, planar square (Ir-4), and prism (Ir-6) to higher energy isomers. The change in the stability order between the two competing protected systems is feasible if the balance between the interaction energy (additive term) and distortion energies (nonadditive terms) compensates for the relative total energies of the unprotected configurations. For all systems, the interaction energy is the main reason responsible for stability alterations, except for 4SO/Ir-4, where the main contribution is from a small penalty due to Ir-4 distortions upon adsorption, and for 4NO/Ir-4, where the energetic effects from the adsorption do not overcome the difference between the binding energies of the unprotected nanoclusters. Finally, from energy decomposition and Hirshfeld charge analysis, we find a predominant covalent nature of the physical contributions in mOX...Ir-n interactions with a cationic core (Ir-n) and an anionic shell (XO coverage). (AU)

• Processo FAPESP: 17/24856-2 - O Mecanismo da Reação de Substituição do Ligante Nitrosil por Aqua em Compostos de Coordenação de Rutênio
• Beneficiário: Renato Pereira Orenha
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado