Activation of Methane by Rhodium Clusters on a Model Support C20H10

• Published in: The journal of physical chemistry letters 2023-10, Vol.14 (41), p.9192-9199
• Main Authors: Zhao, Xi-Guan, Zhao, Zhong-Pu, Zhao, Yan-Xia, He, Sheng-Gui
• Format: Article
• Language: English
• Subjects: Physical Insights into Chemistry, Catalysis, and Interfaces
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.3c02277

Supported metals represent an important family of catalysts for the transformation of the most stable alkane, methane, under mild conditions. Here, using state-of-the-art mass spectrometry coupled with a newly designed double ion trap reactor that can run at high temperatures, we successfully immobilize a series of Rh n – (n = 4–8) cluster anions on a model support C20H10. Reactivity measurements at room temperature identify a significantly enhanced performance of large-sized Rh7,8C20H10 – toward methane activation compared to that of free Rh7,8 –. The “support” acting as an “electron sponge” is emphasized as the key factor to improve the reactivity of large-sized clusters, for which the high electron-withdrawing capability of C20H10 dramatically shifts the active Rh atom from the apex position in free Rh7 – to the edge position in “supported” Rh7 – to enhance CH4 adsorption, while the flexibility of C20H10 to release electrons further promotes subsequent C–H activation. The Rh atoms in direct contact with the support serve as electron-relay stations for electron transfer between C20H10 and the active Rh atom. This work not only establishes a novel approach to prepare and measure the reactivity of “supported” metal clusters in isolated gas phase but provides useful atomic-scale insights for understanding the chemical behavior of carbon (e.g., graphene)-supported metals in heterogeneous catalysis.