Atomistic and electronic structure of metal clusters supported on transition metal carbides: implications for catalysis

30 September 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Novel research avenues have been explored over the last decade on the use of transition metal carbides (TMCs) as catalytically active supports for metal nanoclusters, which display high catalytic activity despite the poor reactivity (or even inertness) of the bulk metal. It has been postulated that TMCs polarise the electron density of adsorbed metal particles in such a way that their catalytic activity ends up being superior to those dispersed on more traditional metal oxide supports. Herein, we investigate the structural and electronic properties of small clusters of precious metals (Rh, Pd, Pt and Au) and more affordable metals (Co, Ni and Cu) supported on TMCs with 1:1 stoichiometry (TiC, ZrC, HfC, VC, NbC, TaC, MoC and WC) by means of periodic Density Functional Theory calculations. Our high-throughput screening studies indicate that it is possible not only to have strongly bonded and stably dispersed metal nanoparticles on TMC surfaces, but also to manipulate their charge by carefully selecting elements with desired electronegativity for the host TMC and the metal cluster. By doing so, it is possible to tune the amount of charge density on the cluster hollow sites, which can facilitate the bonding of certain molecules. Moreover, we identify Pt, Pd and Rh clusters supported on hexagonal TMC (001) facets as the candidates with the highest potential catalytic activity -as estimated by the significant polarisation of the cluster electron density- and stability -as quantified by the strongly negative values of adsorption energy per atom and formation energy-.

Keywords

transition metal carbides
density functional theory
supported clusters
heterogeneous catalysis
electronic structure

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Electronic Supplementary Information for the article entitled "Atomistic and electronic structure of metal clusters supported on transition metal carbides: implications for catalysis", which includes comparison between calculated and experimental lattice parameters, additional details on the convergence with respect to k-points and vacuum length, additional figures on the binding strength of the supported clusters, a discussion on the vertical displacement of surface C atoms upon cluster adsorption, Bader charges on surface C atoms, and charge density difference plots.
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