On the reactivity of low coordinated atoms on foreign solid substrates as models of single atom catalysts

TL;DR

This study uses DFT calculations to explore the reactivity of low-coordinated single metal atoms on various supports, aiming to identify activity descriptors for single atom catalysts, which are crucial for cost-effective catalytic systems.

Contribution

It provides a comprehensive analysis of the reactivity of supported single metal atoms and discusses the challenges in defining universal activity descriptors.

Findings

CO adsorption correlates with d-band center and charge of adatoms.

Weakly bonded atoms tend to bind CO more strongly.

Stability and anchoring are key for effective descriptor-based catalyst design.

Abstract

Catalysis has entered everyday life through a number of technological processes relying on different catalytic systems. The increasing demand for such systems requires rationalization of the use of their expensive components, like noble metal catalysts. As such, a catalyst with low noble metal concentration, in which each one of the noble atoms is active, would reach the lowest price possible. Nevertheless, there are no reactivity descriptors outlined for this type of low coordinated supported atoms. Using DFT calculations, we consider three diverse systems as models of single atom catalysts. We investigate monomers and bimetallic dimers of Ru, Rh, Pd, Ir and Pt on MgO(001), Cu adatom on thin Mo(001)-supported films (NaF, MgO and ScN) and single Pt adatoms on oxidized graphene surfaces. Reactivity of these metal atoms was probed by CO. In each case we see the interaction through the donation-backdonation mechanism. In some cases the CO adsorption energies can be linked to the position of the d-band center and the charge of the adatom. Higher positioned d-band center and less charged supported single atoms bind CO weaker. Also, in some cases metal atoms less strongly bonded to the substrate bind CO more strongly. The results suggest that the identification of common activity descriptor(s) for single metal atoms on foreign supports is a difficult task with no unique solution. However, it is also suggested that the stability of adatoms and strong anchoring to the support are prerequisites for the application of descriptor-based search for novel single atom catalysts.