On the Stability of Cu₅ Catalysts in Air Using Multireference Perturbation Theory

Abstract

An ab initio study of the interaction of O 2 , the most abundant radical and oxidant species in the atmosphere, with a Cu 5 cluster, a new generation atomic metal catalyst, is presented. The open-shell nature of the reactant species is properly accounted for by using the multireference perturbation theory, allowing the experimentally confirmed resistivity of Cu 5 clusters toward oxidation to be investigated. Approximate reaction pathways for the transition from physisorption to chemisorption are calculated for the interaction of O 2 with quasi-iso-energetic trapezoidal planar and trigonal bipyramidal structures. Within the multireference approach, the transition barrier for O 2 activation can be interpreted as an avoided crossing between adiabatic states (neutral and ionic), which provides new insights into the charge-transfer process and gives better estimates for this hard to localize and therefore often neglected first intermediate state. For Cu 5 arranged in a bipyramidal structure, the O–O bond cleavage is confirmed as the rate-determining step. However, for planar Cu 5 , the high energy barrier for O 2 activation, related to a very pronounced avoided crossing when going from physisorption to chemisorption, determines the reactivity in this case.

Increasing the optical response of TiO2 and extending it into the visible region through surface activation with highly stable Cu5 clusters

“…This stability of ‘atomic’ or sub-nanometer-sized Cu clusters is in stark contrast with the irreversible oxidation observed for larger Cu clusters or plasmonic nanoparticles (≈2 nm), as recently reported by Corma's group 24. Moreover, we have also observed that Cu 5 clusters deposited onto TiO 2 are stable against irreversible oxidation via the formation of CuO x oxides at temperatures higher than 700 °C,25 and display very interesting properties for electrochemical applications 26,27. In this article, we study the impact of the deposition of Cu 5 atomic clusters on the optical properties of titanium oxide, providing a thorough theoretical analysis followed by its experimental validation.…”

“…Therefore, any diffusion of clusters deposited on TiO 2 can be neglected in the given case. In fact, as stated in the introduction, the diffusion of Cu 5 clusters (and with it their agglomeration to larger, more easily oxidized nanoparticles) is observed only at temperatures as high as ≈700 °C 25. Moreover, at the adsorbed global minimum configuration shown in Fig.…”

“…Hence, our results demonstrate that the copper cluster acts as an electron donor. However, it is not oxidized through the formation of CuO x oxides at temperatures lower than 700 °C 25…”

DpgC‐Catalyzed Peroxidation of 3,5‐Dihydroxyphenylacetyl‐CoA (DPA‐CoA): Insights into the Spin‐Forbidden Transition and Charge Transfer Mechanisms**

“…For efficiency reasons, the geometries were first optimized at a DFT level using the B3LYP functional, and the D3 version of Grimme's dispersion correction, following by single‐point MRCI calculations. This procedure is similar to the approach employed to shed light on the reactivity of metallic clusters [83, 84] . The only difference is that here, the MECP was also optimized.…”

Outstanding Nobility Observed in Cu5 Clusters Reveals the Key Role of Collective Quantum Effects

“…It is interesting that this collective effect favors the charge transfer from the Cu 5 cluster to the O 2 molecules when the number of O 2 molecules increases. For instance, when only one O 2 is chemisorbed at the bridge adsorption site located at the equatorial plane of the Cu 5 cluster, only a partial charge transfer is observed 1. On one hand, this partial charge transfer arises from the very favorable overlap of the π * orbital from the oxygen atoms, located at the equatorial plane of the cluster, with several d−type orbitals of the copper atoms.…”