Tunneling effects in confined gold nanoparticle hydrogenation catalysts

Luza, Leandro; Gual, Aitor; Fernandes, Jesum Alves; Eberhardt, Dario; Dupont, Jairton

Abstract

Clean surface gold nanoparticles (AuNPs) of ?6.6 nm that were confined in ionic liquid (IL) cages of hybrid ?-alumina (?-Al2O3) displayed hydrogenation pathways in the reduction of trans-cinnamaldehyde distinct from those imprinted directly onto ?-Al2O3. Hydrogen activation proceeded via homolytic activation in IL-encapsulated AuNPs and via heterolytic cleavage for IL-free supported AuNPs. Higher negative apparent entropy (?Sapp) values were obtained for the IL-confined AuNPs compared to the non-hybrid catalyst (Au/?-Al2O3), suggesting a decrease in the number of microstates induced by the nano-confined environment. High kinetic isotope effect (KIE) values (kH/kD = 2.5-2.9 at 273 K) and Arrhenius convex curves were observed. Furthermore, differences of 5.6 and 6.2 kJ mol-1 between the apparent activation energies of the deuteration and hydrogenation reactions (E-E) associated with pre-exponential factor ratios (AD/AH) of 4.6 and 5.1 provided strong evidence of the possible involvement of a tunneling pathway in the case of the confined AuNPs.

• Journal Article Type: Article
• Acceptance Date: Jul 9, 2019
• Online Publication Date: Jul 9, 2019
• Publication Date: Aug 14, 2019
• Deposit Date: Nov 7, 2019
• Publicly Available Date: Jul 10, 2020
• Journal: Physical chemistry chemical physics : PCCP
• Print ISSN: 1463-9076
• Electronic ISSN: 1463-9084
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 21
• Issue: 30
• Pages: 16615-16622
• DOI: https://doi.org/10.1039/c9cp03012c
• Keywords: Physical and Theoretical Chemistry; General Physics and Astronomy
• Public URL: https://nottingham-repository.worktribe.com/output/2469117
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2019/CP/C9CP03012C#!divAbstract
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Leandro Luza (ORCID); : Leandro Luza (ResearcherID); : Aitor Gual (ORCID); : Aitor Gual (ResearcherID); : Jesum Alves Fernandes (ORCID); : Jesum Alves Fernandes (ResearcherID); : Dario Eberhardt (ORCID); : Dario Eberhardt (ResearcherID); : Jairton Dupont (ORCID); : Jairton Dupont (ResearcherID); : Single-blind; : Received 28 May 2019; Accepted 9 July 2019; Accepted Manuscript published 9 July 2019; Advance Article published 18 July 2019; Version of Record published 31 July 2019