Vapor-Phase Self-Assembly to Generate Single Atom Catalysts with Weak Metal-Support Interaction

Abstract

Preparation of thermally-stable metal single atom catalysts (SACs) is a challenge in heterogeneous catalysis, especially on conventional supports that provide a weak metal-support interaction. In this work, we report that conventional support MgAl2O4 can stabilize Pt single atoms by a mechanism of vapor-phase self-assembly when using a potassium-containing salt at a high temperature treatment (800 oC, air). The obtained Pt/K/MgAl2O4 SAC has a high surface area of ca. 100 m2/g, which is ten times higher than that when supported on ceria with strong metal-support interaction involving the same method. We found that the Pt single atoms via this vapor-phase self-assembly preferentially locate at the MgAl2O4 (111) plane for the Pt/K/MgAl2O4 SAC. The experimental results on the formation mechanism and the structure are discussed and validated by density functional theory calculations and ab initio molecular dynamics simulations. We infer that stable triangular K3O3 structures help to stabilize Pt single atoms at high temperatures in oxidizing conditions, showing the higher reactivity than a Pt/CeO2 single atom catalyst in methane oxidation. The obtained Pt/K/MgAl2O4 SAC presents excellent stability in methane oxidation after steam treatment at elevated temperature, whereas a Pt/MgAl2O4 suffers from rapid deactivation due to Pt nanoparticle growth. This work paves the way for preparing thermally-stable and highly active SACs using conventional high-surface-area supports, despite providing only a weak metal-support interaction.