Alloy Catalyst Design beyond the Volcano Plot by Breaking Scaling Relations

Chukwudi F. Nwaokorie,Matthew M. Montemore

doi:10.1021/acs.jpcc.1c10484

Abstract

Volcano plots have been successful in catalyst design and are widely used but also limit the maximum catalytic performance. Volcano plots arise due to scaling relations, which are linear relationships between adsorption energies. Because alloy surfaces can break scaling relations, alloy surfaces may not follow the volcano plot paradigm. Here, we show that alloy surfaces can achieve calculated catalytic performance beyond the volcano plot maximum using methane steam reforming as an example. Using an efficient screening method, we show how to design highly efficient catalysts using the breaking of scaling relations as a design principle. These results show that designing alloys to break scaling relations can give high catalytic performance and that moving beyond simple descriptors can give more accurate predictions of rates.

Highlights

The effectiveness of catalyst surfaces is determined by the forming and breaking of bonds between the catalyst surface and the various intermediates and transition states
To demonstrate the utility of breaking scaling relations, we focus on methane steam reforming an industrially important reaction that converts methane and steam into synthesis gas
We searched for alloy surfaces that break scaling relations, such that they have strong CH3 adsorption and weak C adsorption

Summary

Introduction

The effectiveness of catalyst surfaces is determined by the forming and breaking of bonds between the catalyst surface and the various intermediates and transition states. Previous studies have shown that for similar intermediates the strengths of these chemical bonds, i.e., the adsorption energies, are often correlated across different metal surfaces.[1] These correlations, known as scaling relations, arise from similarities in the effect of the surface’s electronic structure on certain adsorbates.[2] Scaling relations have been widely used in rationalizing catalyst performance or in designing new catalysts.[3−5]. If the interaction is instead too strong, the product fails to desorb.[6] The ideal catalyst would activate the reactants but give a relatively weak binding of the intermediates to avoid overcrowding the surface, but this optimal scenario is traditionally difficult to achieve in heterogeneous catalysis due to these linear correlations. Some computational studies suggest that exceeding the volcano plot using a combination of homogeneous surfaces may be difficult or impossible.[7,8] scaling relations are very useful in understanding catalyst performance and screening catalytic surfaces, but they impose limitations on the optimum activities of catalysts.[7,8]

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Conclusion