Palladium, platinum, and their alloys are promising catalysts
for
electrochemical CO2reduction 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, CO2activation and
dissociation mechanisms on PdxPt4–xclusters 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 CO2activation 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 CO2dissociation; in fact, our computations unveiled several dissociated
CO2isomers 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 CO2one (activated
state). On the basis of the comparison of the PdxPt4–xreaction paths, we
can observe the promising catalytic activity of Pd3Pt in
the studied context. Not only does this cluster composition favor
CO2activation against dissociation (thereby expected to
facilitate the hydrogenation reactions of CO2), the potential
energy surface (PES) is very flat among activated CO2isomers.