Multistep CO2 Activation and Dissociation Mechanisms on PdxPt4- x Clusters in the Gas Phase

Renata Sechi; Tibor Höltzl

doi:10.1021/acs.jpca.2c08333

Multistep CO₂ Activation and Dissociation Mechanisms on Pd_xPt_{4- x} Clusters in the Gas Phase

J Phys Chem A. 2023 Jun 1;127(21):4596-4608. doi: 10.1021/acs.jpca.2c08333. Epub 2023 May 17.

Authors

Renata Sechi^{1

2}, Tibor Höltzl^{1

3

2}

Affiliations

¹ Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4, Budapest 1111, Hungary.
² Furukawa Electric Institute of Technology, Késmárk utca 28/A, Budapest 1158, Hungary.
³ ELKH-BME Computation Driven Chemistry Research Group, Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rkp. 3, Budapest 1111, Hungary.

Abstract

Palladium, platinum, and their alloys are promising catalysts for electrochemical CO₂ reduction reactions (CO₂RR), leading to the design of durable and efficient catalysts for the production of useful chemicals in a more sustainable way. However, a deep understanding of the CO₂RR mechanisms is still challenging because of the complexity and the factors influencing the system. The purpose of this study is to investigate at the atomic scale the first steps of the CO₂RR, CO₂ activation and dissociation mechanisms on Pd_xPt_4-x clusters in the gas phase. To do it, we use Density Functional Theory (DFT)-based reaction path and ab initio molecular dynamics (AIMD) computations. Our research focuses on the description of CO₂ activation and dissociation processes via the computation of multistep reaction paths, providing insights into the site and binding mode dependent reactivity. Detailed understanding of the CO₂-cluster interaction mechanisms and estimating of the reaction energy barriers facilitate comprehension of why and how catalysts are poisoned and identification of the most stable activated adducts configurations. We show that increasing the platinum content induces fluxional behavior of the cluster structure and biases CO₂ dissociation; in fact, our computations unveiled several dissociated CO₂ isomers that are very stable and that there are various isomerization processes leading to a dissociated structure (possibly a CO poisoned state) from an intactly bound CO₂ one (activated state). On the basis of the comparison of the Pd_xPt_4-x reaction paths, we can observe the promising catalytic activity of Pd₃Pt in the studied context. Not only does this cluster composition favor CO₂ activation against dissociation (thereby expected to facilitate the hydrogenation reactions of CO₂), the potential energy surface (PES) is very flat among activated CO₂ isomers.