Mechanistic Insights on the Semihydrogenation of Alkynes over Different Nanostructured Photocatalysts

Wang, Bowen; Lanterna, Anabel E.; Scaiano, Juan C.

Abstract

A single molecule microscopy study of the interaction of dye-modified alkanes, alkenes and alkynes with nanostructured catalysts based on TiO 2 reveals significant differences in the desorption kinetics of the probe molecules depending on the chemical nature of the catalyst. A comparison of TiO 2 with materials decorated with palladium (Pd@TiO 2) or molybdenum/cobalt (MoCo@TiO 2) reveals kinetic differences that justify in part the better performance of MoCo@TiO 2 in semi-hydrogenation reactions. Whereas single-molecule desorption rate is ~50% higher for MoCo@TiO 2 than Pd@TiO 2 , analysis at the bench scale indicate alkene-to-alkane conversion is about 10 times faster for Pd (k 2 Pd = 0.02 s-1) than for MoCo (k 2 MoCo = 0.002 s-1) catalysts. This suggests selectivity is not solely determined by the desorption processes and that the hydrogenation rate constant (k 21) for the on-surface hydrogenation of alkenes to alkanes is much faster for Pd@TiO 2 than for MoCo@TiO 2. Thus, the latter shows greater selectivity towards 2 partial hydrogenation reactions compared with Pd@TiO 2 , whose excellent hydrogenation performance becomes a disadvantage for the selectivity needed for semi-hydrogenation processes.

Citation

Wang, B., Lanterna, A. E., & Scaiano, J. C. (2021). Mechanistic Insights on the Semihydrogenation of Alkynes over Different Nanostructured Photocatalysts. ACS Catalysis, 11(7), 4230-4238. https://doi.org/10.1021/acscatal.0c05233

• Journal Article Type: Article
• Acceptance Date: Mar 9, 2021
• Online Publication Date: Mar 19, 2021
• Publication Date: Mar 19, 2021
• Deposit Date: Mar 15, 2021
• Publicly Available Date: Mar 20, 2022
• Journal: ACS Catalysis
• Electronic ISSN: 2155-5435
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 7
• Pages: 4230-4238
• DOI: https://doi.org/10.1021/acscatal.0c05233
• Keywords: Semi-hydrogenation; photocatalysis; molybdenum; palladium; titania
• Public URL: https://nottingham-repository.worktribe.com/output/5396623
• Publisher URL: https://pubs.acs.org/doi/10.1021/acscatal.0c05233
• Additional Information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, copyright© American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acscatal.0c05233