Size-dependent strong metal-support interaction in TiO2 supported Au nanocatalysts

Xiaorui Du,Gao Li,Yike Huang,Botao Qiao,Hailian Tang,Yang Su,Mingrun Li,Xiaoli Pan,Qike Jiang,Bing Han

doi:10.1038/s41467-020-19484-4

Abstract

The strong metal-support interaction (SMSI) has long been studied in heterogonous catalysis on account of its importance in stabilizing active metals and tuning catalytic performance. As a dynamic process taking place at the metal-support interface, the SMSI is closely related to the metal surface properties which are usually affected by the size of metal nanoparticles (NPs). In this work we report the discovery of a size effect on classical SMSI in Au/TiO2 catalyst where larger Au particles are more prone to be encapsulated than smaller ones. A thermodynamic equilibrium model was established to describe this phenomenon. According to this finding, the catalytic performance of Au/TiO2 catalyst with uneven size distribution can be improved by selectively encapsulating the large Au NPs in a hydrogenation reaction. This work not only brings in-depth understanding of the SMSI phenomenon and its formation mechanism, but also provides an alternative approach to refine catalyst performance.

Highlights

The strong metal-support interaction (SMSI) has long been studied in heterogonous catalysis on account of its importance in stabilizing active metals and tuning catalytic performance
We report our discovery of the size-dependent SMSI in Au/TiO2 catalyst system where SMSI is more prone to occur on large Au NPs (~9 and ~13 nm) than on small ones (~3 and ~7 nm)
Colloidal Au NPs of ~3 and ~9 nm were synthesized by employing poly(vinylalcohol) (PVA) and oleylamine (OA) as protective agents, respectively, and depositing on commercial TiO2 (P25, 58 m2 g−1) by an adsorption method

Summary

Introduction

The strong metal-support interaction (SMSI) has long been studied in heterogonous catalysis on account of its importance in stabilizing active metals and tuning catalytic performance. A thermodynamic equilibrium model was established to describe this phenomenon According to this finding, the catalytic performance of Au/TiO2 catalyst with uneven size distribution can be improved by selectively encapsulating the large Au NPs in a hydrogenation reaction. SMSI is a dynamic process taking place at the interface between Au NPs and the support, involving electron transfer and mass transport, both of which are closely related to the surface properties of Au NPs. Considering the prominent size-dependent catalytic performance of Au nanocatalysts[26,27,28], whether there is a size effect on SMSI remains an intriguing yet unaddressed issue. It has been proposed that the size of metal cluster may influence the encapsulation of PGMs by TiO218,29,30, but so far no exclusive demonstration was reported It was recently reported by Hutchings group that the smaller and poorly alloyed Pd-rich NPs are more susceptible to be encapsulated by SnOx than larger Pd–Sn alloy particles[31].

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Results

Conclusion