Ethylene el dorado: Gold(I) unusually takes up three ethylene molecules in a spoked‐wheel arrangement (see picture). The complex was synthesized as the hexafluoroantimonate salt and structurally characterized.
The understanding
of quantum correlations within catalysts is an
active and advanced research field, absolutely necessary when attempting
to describe all the relevant electronic factors in catalysis. In our
previous research, we came to the conclusion that the most promising
electronic interactions to improve the optimization of technological
applications based on magnetic materials are quantum spin exchange
interactions (QSEI), nonclassical orbital mechanisms that considerably
reduce the Coulomb repulsion between electrons with the same spin.
QSEI can stabilize open-shell orbital configurations with unpaired
electrons in magnetic compositions. These indirect spin-potentials
significantly influence and differentiate the catalytic properties
of magnetic materials. As a rule of thumb, reaction kinetics (thus
catalytic activity) generally increase when interatomic ferromagnetic
(FM) interactions are dominant, while it sensibly decreases when antiferromagnetic
(AFM) interactions prevail. The influence of magnetic patterns and
spin-potentials can be easily spotted in several reactions, including
the most important biocatalytic reactions like photosynthesis, for
instance. Moreover, we add here the concept of quantum excitation
interactions (QEXI) as a crucial factor to establish the band gap
in materials and as a key factor to efficiently mediate electron transfer
reactions. In the present Perspective, we offer a general conceptual
overview, mainly based on our recent research, on the importance of
strongly correlated electrons and their interactions during catalytic
events. We present the physical principles and meanings behind quantum
exchange in a way that facilitates a comprehensive understanding of
the electronic interactions in catalysis from their quantum roots;
we explore the issue via mathematical treatment as well as via intuitive
visual space/time diagrams to expand the potential readership beyond
the domain of physicists and quantum chemists.
One of the main obstacles in the implementation of hydrogen fuel cells (HFC) lies in the efficiency loss due to the overpotential of the oxygen reduction reaction (ORR). Nowadays, the best catalysts for cathodes in HFC are Pt 3 Co nanostructures. The superior activity of these magnetic Pt-alloys, compared to metallic platinum, correlates with the milder chemisorption of the oxygenated intermediates on the surfaces of the alloy. Quantum spin exchange interactions (QSEI), including interlayer exchange coupling due to magnetic inner Co layers, are determinant to make the active sites prone to bind adsorbed oxygen atoms in an optimal fashion for catalytic activity. We present a study on antiferromagnetic (AFM) and ferromagnetic (FM) Pt 3 Co (111) nanostructures conducted via spin-polarized DFT+U calculations. The study begins with a thorough screening of AFM, FM, and fictitious closed-shell Pt 3 Co slab models with different atomic distributions ranked in order of stability. The chemisorption enthalpy values of O* and H* atoms on the most stable AFM (A-type) and FM nanolayers show weaker binding of the adsorbate compared to isostructural Pt (111) nanolayers. Cooperative spin potentials, associated with open-shell orbital configurations, unequivocally lead to decreased enthalpies of adsorption for H* and O* atoms. Hence, a complete and realistic treatment of the structure−activity relationships in heterogeneous catalysis relies upon the correct evaluation of orbital magnetism: spin-dependent potentials are key factors to design optimal ORR catalysts.
The definition of the interplay between chemical composition, electro-magnetic configuration and catalytic activity requires a rational study of the orbital physics behind active materials.
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