Directing reaction pathways via in situ control of active site geometries in PdAu single-atom alloy catalysts

Mengyao Ouyang,Konstantinos G Papanikolaou,Georgios Giannakakis,Adam S Hoffman,Simon R Bare,E Charles H Sykes,Alexey Boubnov,Michail Stamatakis,Maria Flytzani-Stephanopoulos

doi:10.1038/s41467-021-21555-z

Abstract

The atomic scale structure of the active sites in heterogeneous catalysts is central to their reactivity and selectivity. Therefore, understanding active site stability and evolution under different reaction conditions is key to the design of efficient and robust catalysts. Herein we describe theoretical calculations which predict that carbon monoxide can be used to stabilize different active site geometries in bimetallic alloys and then demonstrate experimentally that the same PdAu bimetallic catalyst can be transitioned between a single-atom alloy and a Pd cluster phase. Each state of the catalyst exhibits distinct selectivity for the dehydrogenation of ethanol reaction with the single-atom alloy phase exhibiting high selectivity to acetaldehyde and hydrogen versus a range of products from Pd clusters. First-principles based Monte Carlo calculations explain the origin of this active site ensemble size tuning effect, and this work serves as a demonstration of what should be a general phenomenon that enables in situ control over catalyst selectivity.

Highlights

The atomic scale structure of the active sites in heterogeneous catalysts is central to their reactivity and selectivity
We demonstrate how in situ control of the active sites with CO can be used to transition the catalyst from a single-atom alloy (SAA) phase that is selective to acetaldehyde and hydrogen to a Pd cluster phase which leads to the formation of CO, ethyl acetate, and CH4 as byproducts in the ethanol dehydrogenation (EDH) reaction
A primary consideration for designing a working SAA catalyst is whether the catalytically active atoms will be stable in the surface layer of the nanoparticle and accessible to the reactants

Summary

Introduction

The atomic scale structure of the active sites in heterogeneous catalysts is central to their reactivity and selectivity. We demonstrate how in situ control of the active sites with CO can be used to transition the catalyst from a SAA phase that is selective to acetaldehyde and hydrogen to a Pd cluster phase which leads to the formation of CO, ethyl acetate, and CH4 as byproducts in the ethanol dehydrogenation (EDH) reaction.

Results

Conclusion