Quantifying the origin of inter-adsorbate interactions on reactive surfaces for catalyst screening and design

Abstract

The adsorption energy of reactant molecules and reaction intermediates is one of the key descriptors of catalytic activity of surfaces and is commonly used as a metric in screening materials for design of heterogeneous catalysts. The efficacy of such screening schemes depends on the accuracy of calculated adsorption energies under reaction conditions. These adsorption energies can depend strongly on interactions between adsorbed molecules in the adlayer. However, these interactions are typically not accounted for in screening procedures that use DFT-based zero-coverage adsorption energies. Identifying the physical mechanisms behind these interactions is essential to model realistic catalyst surfaces under reaction conditions and to understand the dependence of adsorption energies on reaction parameters like surface strain and composition. This article describes a method to quantitatively resolve the observed inter-adsorbate interactions into various direct adsorbate-adsorbate interactions (i.e. Coulombic and steric) and surface-mediated interactions (i.e. adsorbate-induced surface relaxation and change in electronic structure) by combining density functional theory and cluster-expansion calculations of coverage-dependent adsorption energies. The approach is implemented on a model catalyst surface of FeS2(100) reacting with H2S molecules. We find that the adsorption energy of H2S molecules can be affected by over 0.55 eV by the repulsive inter-adsorbate interactions caused primarily by the adsorbate-induced changes to the electronic structure of the FeS2 surface. These interactions also show a strong monotonic dependence on surface strain, being three times stronger on compressively strained surfaces than on surfaces under tensile strain. The large magnitude of inter-adsorbate interactions as well as their strong dependence on lattice strain demonstrate the need for using coverage-dependent adsorption energies for more accurate screening, for example for strained catalytic systems like core-shell and overlayer structures.

Redox-Switchable Allosteric Effects in Molecular Clusters

“…For example, inter-adsorbate interactions inhibit CO adsorption at nearest-neighbor sites on Cu(100) due to decreased electron density around the initial CO adsorption site . Similar effects are invoked as the major contributors for the coverage-dependent adsorption energy of H 2 S on FeS 2 . Inspired by inter-adsorbate effects in extended materials, we set out to probe if site-differentiation of a molecular cluster could also be achieved based solely on ligand binding and to investigate if redox state changes can be used as a switch for this differentiation.…”

Caught in the Act of Substitution: Interadsorbate Effects on an Atomically Precise Fe/Co/Se Nanocluster

“…Substrate adsorption is an elementary step in any surface-based chemical transformation and can dramatically alter electronic properties , or invoke surface restructuring within the lattice. − But even the simplest coordinative process is complex when considered at an inorganic surface, where an ensemble of interconnected active sites compete for substrate binding . For example, ligand binding differentiates chemically degenerate surface sites as steric and inductive effects give rise to interadsorbate interactions. Although scarcely understood at the atomic level, interadsorbate effects have macroscopic outcomes, modulating catalytic activity, − and even promoting long-range substrate ordering. , From a molecular point of view, interadsorbate forces guide the reactivity of neighboring surface sites in a manner similar to how directing groups guide substitution patterns in organic synthesis, activating or deactivating neighboring sites at specific locations.…”

“… 4 − 9 But even the simplest coordinative process is complex when considered at an inorganic surface, where an ensemble of interconnected active sites compete for substrate binding. 10 For example, ligand binding differentiates chemically degenerate surface sites as steric 11 and inductive 12 effects give rise to interadsorbate interactions. Although scarcely understood at the atomic level, interadsorbate effects have macroscopic outcomes, modulating catalytic activity, 13 − 15 and even promoting long-range substrate ordering.…”