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Magnetism in a chemical compound is the macroscopic result of the couplings of the spins of electrons within in it [...]

Thorough analyses of structural factors in catalysis are interesting because they allow the massive prescreening of potential optimum compositions. Overall, this article shows how the orbital physics of magnetic compositions relates with spin–lattice interactions and then band gaps and bond lengths together become relevant descriptors in catalytic oxygen technologies. Active electrocatalysts for the oxygen evolution reaction (OER) include magnetic oxides with metals at relatively high oxidation states, so chemisorbed molecular O2 is not very stable. On the other hand, ideal compositions for the oxygen reduction reaction (ORR) have metals in a comparatively lower oxidation state, which can supply electrons to activate O2 molecules toward electron-richer oxygen atoms. Spin–lattice interactions in these strongly correlated oxides relate the orbital configurations and oxidation state with distinctive metal–oxygen bond distances, indicating localized or itinerant electronic behavior and selectivity in oxygen e...

Bimetallic Pt-based alloys have drawn considerable attention in the last decades as catalysts in proton-exchange membrane fuel cells (PEMFCs) because they closely fulfill the two major requirements of high performance and good stability under operating conditions. Pt3Fe, Pt3Co, and Pt3Ni stand out as major candidates, given their good activity toward the challenging oxygen reduction reaction (ORR). The common feature across catalysts based on 3d-transition metals and their alloys is magnetism. Ferromagnetic spin-electron interactions, quantum spin-exchange interactions (QSEIs), are one of the most important energetic contributions in allowing milder chemisorption of reactants onto magnetic catalysts, in addition to spin-selective electron transport. The understanding of the role played by QSEIs in the properties of magnetic 3d-metal-based alloys is important to design and develop novel and effective electrocatalysts based on abundant and cheap metals. We present a detailed theoretical study (via density functional theory) on the most experimentally explored bimetallic alloys Pt3M (M = V, Cr, Mn, Fe, Co, Ni, and Y)(111). The investigation starts with a thorough structural study on the composition of the layers, followed by a comprehensive physicochemical description of their resistance toward segregation and their chemisorption capabilities toward hydrogen and oxygen atoms. Our study demonstrates that Pt3Fe(111), Pt3Co(111), and Pt3Ni(111) possess the same preferential multilayered structural organization, known for exhibiting specific magnetic properties. The specific role of QSEIs in their catalytic behavior is justified via comparison between spin-polarized and non-spin-polarized calculations.

Oxygen evolution and reduction reactions play a critical role in determining the efficiency of the water cycling (H2O ⇔ H2 + 1/2O2), in which the hydrogen serves as the energy carrier. That calls for a comprehensive understanding of oxygen electrocatalysis for efficient catalyst design. Current opinions on oxygen electrocatalysis have been focused on the thermodynamics of the reactant/intermediate adsorption on the catalysts. Because the oxygen molecule is paramagnetic, its production from or its reduction to diamagnetic hydroxide/water involves spin-related electron transfer. Both electron transfer and orbital interactions between the catalyst and the reactant/intermediate show spin-dependent character, making the reaction kinetics and thermodynamics sensitive to the spin configurations. Herein, a brief introduction on the spintronic explanation of the catalytic phenomena on oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is given. The local spin configurations and orbital interactions in the benchmark transition-metalbased catalysts for OER and ORR are analyzed as examples. To further understand the spintronic oxygen electrocatalysis and to develop more efficient spintronic catalysts, the challenges are summarized and future opportunities proposed. Spin electrocatalysis may emerge as an important topic in the near future and help integrate a comprehensive understanding of oxygen electrocatalysis. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version This work was supported by Singapore Ministry of Education Tier 2 Grant (MOE- 2018-T2-2-027).

Electrons in covalent oxides are fermions interacting through overlapping atomic orbitals, and quantum exchange interactions incorporate influential spin-dependent potentials in their electrocatalytic properties. The Goodenough-Kanamori rules explain the magnetic coupling between metals connected via ligands, known as super- (or double-) exchange interactions, which regulate their charge transport properties. To describe the electrocatalytic activity of magnetic metal oxides, we must extend their spin-dependent mechanisms of electron tunnelling to catalytic interfaces, because the exchange coupling between orbitals, in the catalysts and with the chemisorbed reactants, influences the kinetics of electron transfer reactions. The principles for developing magnetic coupling rules in electrocatalysis must guarantee spin passages, which are optimum for intrinsically degenerate configurations of the frontier orbitals oriented in the direction of the bonds at both sides of the Fermi level. A continuous energy landscape between the reactants and the catalyst minimizes the overpotentials during coherent redox electron tunnelling. Consequently, in this paper we derive the guidelines of the ferromagnetic (FM) exchange interactions, an extension of the Goodenough-Kanamori rules, to electrocatalytic interfaces, which anticipates minimum Gibbs energy of activation. We focus on the electronic coordinates, targeting reaction conditions where the electrons are the main energy carriers to trigger the steps; nonetheless they are inter-related with the atomic movements. We will use the oxygen evolution and reduction reactions as examples where quantum exchange interactions, a landmark of solid-state magnetism, and the chemistry of the triplet state O 2 molecule, are crucial for optimum kinetics. One sentence summary: Delocalizing spin potentials facilitate the coherent propagation of electrons at covalent magnetic interfaces; this is a physical principle that links ferromagnetic exchange interactions, antibonding orbitals and optimum viable electrocatalysis: spintro-catalysis.

The study of magnetic perovskite oxides has led to novel and very active compounds for O2 generation and other energy applications. Focusing on three different case studies, we summarise the bulk electronic and magnetic properties that initially serve to classify active perovskite catalysts for the oxygen evolution reaction (OER). Ab-initio calculations centred on the orbital physics of the electrons in the d-shell provide a unique insight into the complex interplay between spin dependent interactions versus selectivity and OER reactivity that occurs in these transition-metal oxides. We analyse how the spin, orbital and lattice degrees of freedom establish rational design principles for OER. We observe that itinerant magnetism serves as an indicator for highly active oxygen electro-catalysts. Optimum active sites individually have a net magnetic moment, giving rise to exchange interactions which are collectively ferromagnetic, indicative of spin dependent transport. In particular, optimum active sites for OER need to possess sufficient empty orthogonal orbitals, oriented towards the ligands, to preserve an incoming spin aligned electron flow. Calculations from first principles open up the possibility of anticipating materials with improved electro-catalytic properties, based on orbital engineering.

The orbital physics relevant in electrocatalytic activity present subtle differencies between oxygen evolution (OER) and reduction reactions (ORR). Achieving maximum efficiency in (electro)catalysis requires a detailed understanding on the electronic interactions. Quantum correlations and, in particular, spin-exchange interactions are decisive to understand the necessary underlying physics. Besides adsorption energies of reaction intermediates, there are other critical factors to characterize electrocatalysts such as charge, spin and flow sense of the electron transport. A revolution is going on right now in the understanding of oxygen electrochemistry, meant to close the gap with the novel research in strongly correlated materials or spintronics and to re-establish general fundaments of catalysis. We present a concise review taking as central example the dual catalyst LaNi0.8Fe0.2O3.

The oxygen evolution complex (OEC) of photosystem II (PSII) is intrinsically more active than any synthetic alternative for the oxygen evolution reaction (OER). A crucial question to solve for the progress of artificial photosynthesis is to understand the influential interactions during water oxidation in PSII. We study the principles of interatomic electron transfer steps in OER, with emphasis on exchange interactions, revealing the influence of delocalizing ferromagnetic spin potentials during the catalytic process. The OEC is found to be an exchange coupled mixed-valence electron-spin acceptor where its orbital physics determine the unique activity of PSII. The two unpaired electrons needed in the triplet O2 molecule interact with the high spin state of the catalyst via exchange interactions; the optimal ferromagnetic catalyst and the resulting radical intermediates are spin paired. As a result, the active center of the CaMn4O5 cofactor, stimulated by the driving potential provided by photons, works as...

Manganese oxides with a half-metallic ground state are particularly active for oxygen reduction reactions (ORR). La0.67Sr0.33MnO3 (LSMO) perovskite is the archetypal example for compositions with a Curie temperature (TC) above room temperature, and with a high intrinsic activity for the partial reduction of triplet state O2. The ferromagnetic (FM) character of the superexchange interactions in LSMO facilitates both the charge and spin transport below 370 K. Other than the enhanced electronic conductivity, the reduced spin entropy seems to be of relevance in oxygen catalysis, as the magnetic ordering extends to the surface. The sign of the exchange interactions determines the adsorption of the triplet oxygen molecule with its spin antiparallel to the FM catalysts. On the basis of transition state theory, we report that on LSMO the hindrance due to the magnetic entropy for the initial reduction of O2 by two antiparallel electrons to diamagnetic intermediates (like H2O2) is minimum. On the other hand, the additional reduction of H2O2 to H2O, diamagnetic steps, prefers paramagnetic catalysts, with higher magnetic entropy like La0.4Sr0.6MnO3, to avoid spin accumulation.

Reactions involving nitrogen fixation and transfer are of great industrial interest. In this regard, unveiling all the physical principles that determine their activity would be enormously beneficial for the rational design of novel catalysts with improved performance. Within this context, this work explores the activity of bulk molybdenum-based transition metal nitrides in ammonia synthesis. Our results highlight that the most active compositions show increasing ferromagnetism in the metal-nitrogen bonds, which constitute the active sites. We observe that the total spin accumulated in the bonds at the active sites is a physically meaningful descriptor to discriminate optimum catalysts. Higher activities are associated with ferromagnetic phases, and the underlying reason is an enhanced overlapping of the electronic wavefunctions; which also make the reaction steps spin-sensitive. These finding provides strong evidence of the general influence of electrons magnetic moment in catalysis, being part of the specific field of spintro-catalysis.

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. Apart from Coulomb forces, quantum spin exchange interactions (QSEI) are part of the potentials that differentiate the activity of magnetic oxides, strongly correlated electrocatalysts, in electron transfer reactions. Ferromagnetic (FM) cobalt oxides can show low overpotentials for the oxygen evolution reaction (OER) and the La1XSrXCoO3d (0 r X r 1) family of perovskites is good ground to gain understanding of the electronic interactions in strongly correlated catalysts. In this case, Sr-doping raises the OER activity and the conductivity and increases FM spin moments. The efficiency of electrocatalysts based on Earth-abundant 3d-transition metals correlates with the interrelated factors: mild-bonding energies, the reduction of the electronic repulsions because of the QSEI in the open-shells, and enhanced spin delocalization in FM ordering. The reason for the outstanding OER activity of SrCoO3d is the accumulation of FM holes in the 3d–2p bonds, including the ligand orbitals, thus facilitating spinselected charge transport and production of triplet O2 moieties from the oxidation of diamagnetic precursors. Spin-polarized oxygen atoms in the lattice can participate in O–O coupling and release of O2 in a Mars–Van Krevelen mechanistic fashion. We show that the stabilizing FM QSEI decrease the adsorption and activation energies during oxygen evolution and spin-dependent potentials are one of the factors that govern the catalytic activity of magnetic compositions: spintro-catalysis.

We have performed an in-depth ab initio study of the magnetic structure within the most active perovskites for the oxygen evolution reaction. In all cases, the ground state exhibits an extended antiferromagnetic coupling in the unit cell. Layered antiparallel alignment of the magnetic moments appears to be related to their electrocatalytic activity. All the perovskites calculated within this paper show space-separated charge-transport channels depending on the spin orientation. Comparing the electronic structures with the reported activities, we find a direct correlation between the magnetic accumulation on the spin channels in the bulk material and the catalytic activity. We discuss the possible implications of such observations in terms of magnetic interactions. During oxygen evolution in water electrolysis, reactants and products do not preserve spin. For triplet state oxygen to evolve, the catalyst at the anode can speed up the reaction if it is able to balance the magnetism of the oxygen molecule by extracting electrons with an opposite magnetic moment, conserving the overall spin.

The spin of the electron is decisive to understand electronic interactions in heterogeneous catalysis, mainly because the stabilizing Quantum Spin Exchange Interactions (QSEI) are always a significant contribution to the energy of magnetic catalysts and absorbates during reaction events. Cooperative QSEI in compositions with multi-atomic open-shell configurations (QSEI-OS) maximize the influence of the spin dependent potentials, determining the electronic properties of magnetic materials and shaping their reactivity. In this paper, we explain that because of the intra- and inter- atomic QSEI-OS, high-spin (3d5) antiferromagnetic (AFM) metals like Cr and Mn can be more inert (or “noble”) than Au itself towards the formation of covalent bonds with hydrogen atoms. AFM QSEI-OS lead to a relative higher destabilization of the unoccupied (spin-)orbitals (Mott upper band) in Cr and Mn compared with other metals. In oxygen adsorption, QSEI-OS lead to the reduction of the electronic repulsions in occupied 3d5 orbitals with a concomitant decrease of the chemisorption enthalpy of the oxygen atoms. Since hydrogen and oxygen atoms are the most important intermediates in relevant catalytic processes like oxygen reduction reaction and water splitting, we observe how the effect of QSEI-OS needs to be properly incorporated as a critical factor to understand the activity of catalysts based on magnetic metals.

The technological interest of oxygen reduction and evolution reactions, ORR and OER, for the clean use and storage of energy has resulted in the discovery of multiple catalysts; and the physical and catalytic properties of the most active compositions are only comprehensible with the consideration of magnetic interactions. Spin dependent potentials via exchange interactions, spin-orbit coupling or through magneto-electric effects catalyse the oxygen electrochemistry. The best catalysts show metal sites with localized spins and electron delocalization; a correlation exists between the rate constant for charge transfer reactions and spin-dependent electron mobility. Since during the OER and ORR the number of unpaired electrons is not conserved, magnetic potentials in optimum catalysts act as selective gates to enhance the transport of local spin currents. Overall magnetic potentials can reduce the bonding properties of the, donor or acceptor, orbitals in the catalyst, and electrons more easily transfer over the conduction band. The influence of spin dependent forces is generally applicable to oxygen catalysis, and supplements the physical interactions relevant for inorganic or organic, electro or photo, artificial or natural processes.

International audience; Twelve commercially available bisphosphine ligands have been evaluated in rhodium-catalyzed hydroformylation reactions. All ligands exhibited high chemoselectivities for aldehyde formation. The highest enantioselectivity (53% ee) of styrene hydroformylation was achieved with (S)-BTFM-Garphos (L7) substituted with electron withdrawing substituents. High pressure NMR (HP-NMR) spectroscopy and in situ high pressure IR spectroscopy (HP-IR) were used to study the resting states of the catalyst species in the reactions. The ligand effect on the structures of the observable species was examined. Both electronic and steric factors were considered to contribute to the performance of the various ligands. The results showed that decreasing the phosphine basicity increased the enantioselectivity, while in the systems studied here the steric character plays a less important role than the electronic features in achieving good regioselectivities.

Density functional theory has been used to explore the mechanism of cleavage of H2 at a sulfido-bridged molybdenum cluster, CpMo(μ-SH)(μ-S)(μ-S2CH2)MoCp. The addition occurs across a single Mo-S bond, and the disruption of the strong Mo-S π bonding in the ground state leads to a very high-lying transition state (+43 kcal mol-1). Once formed, the adsorbed hydrogen migrates over the cluster via a series of hops from metal to sulphur, formally corresponding to a switch from hydridic to protic character. The low barrier (+15 kcal mol-1) for migration leads to facile hydrogenolysis of coordinated substrates. © 2005 Elsevier B.V. All rights reserved.

The effect of solvent systems on previously-reported ESI-MS based proton-assisted enantioselective molecular recognition phenomena of tartar emetic, L-antimony(III)-tartrate, was evaluated. This was achieved by carrying out a series of competitive binding experiments using chiral selectors, bis(sodium) D- and -L-antimony(III)-tartrates with chiral selectands, neutral side-chain amino acid enantiomeric isotopomers of alanine (Ala), valine (Val), leucine (Leu) and phenylalanine (Phe), in three different solvent systems, ACN/H2O (75/25 v/v), H2O (100%) and H2O/MeOH (25/75 v/v). Observations from these experiments suggest that the effect of solvent systems on previously reported proton-assisted chiral recognition capacity of D,L-antimony(III)-tartrates is small, but not negligible. It was observed that an ACN/H2O (75/25 v/v) solvent system facilitates and enhances the chiral discrimination capacity of protonated {[D,L-Sb2-tar2][H]}− ionic species. Further, amino acid enantiomers showed a general trend of increasing selectivity order, Val ≤ Ala < Leu ≈ Phe towards the protonated {[D,L-Sb2-tar2][H]}− ionic species which was independent of the solvent system employed. The lack of enantioselective binding for {[D,L-Sb2-tar2]}2− ionic species was consistently recorded in respective mass spectra from all performed experiments, which suggests that ESI-friendly solvent systems have no effect and do not influence this phenomenon. Chirality, 2011. © 2010 Wiley-Liss, Inc.

The facile preparation of a range of supported nanoparticles on porous materials was successfully accomplished through the use of a range of environmentally friendly protocols including a modified impregnation/reduction methodology, ultrasounds and microwave irradiation. Materials were characterised by transmission electron microscopy (TEM) and XPS. Different morphologies including conventional nanospheres, nanoflower aggregates, nanorod-like structures and nanocubes were achieved under different conditions. The reported supported nanoparticles are envisaged to have interesting applications in various areas including catalysis, optics and sensors.

Computational chemistry is used to explore a mechanism for CO hydrogenation to methane on iron carbides. As CO dissociation is endothermic on carbon terminated Fe5C2 (100) cuts, we explore a path starting with the hydrogenation of the surface, which liberates iron 4-fold sites for adsorption and dissociation of CO. The reaction cycle to methane resembles the Mars-van Krevelen mechanism for oxidation reactions.

Ga-, Al- and AlGa-SBA-15 mesoporous materials were synthesized via a direct sol–gel hydrothermal protocol. The SBA-15 materials were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM) and pyridine and 2,6-dimethylpyridine titration. The activity of the Ga- and AlGa-SBA-15 was investigated in the Friedel–Crafts alkylation of toluene with benzyl chloride (promoted by Lewis acidity) and benzyl alcohol (promoted by Bronsted acidity). Quantitative conversion of the starting material was found for all Ga- and AlGa-SBA-15 after a few hours of reaction at 110 °C in the alkylation of toluene with benzyl chloride. The mesoporous acidic materials provided very poor activities in the alkylation of toluene with benzyl alcohol, with the exception of the Al-SBA-15. The activities of the Ga- and AlGa-SBA-15 were correlated to the higher proportion of Lewis compared to Bronsted acid sites. The solid acids were also highly reusable preserving almost their initial catalytic activity after five reuses.

Treatment of [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) with the imido complexes [Ti(NAr)Cl(2)(py)(3)] (Ar=2,4,6-C(6)H(2)Me(3)) and [Ti(NtBu)Cl(2)(py)(3)] in toluene affords the single azatitanocubanes [[Cl(2)(ArN)Ti]( micro(3)-NH)(3)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (2.C(7)H(8)) and [[Cl(2)Ti](micro(3)-N)(2)(micro(3)-NH)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [[M(NtBu)(NHtBu)Cl(2)(NH(2)tBu)](2)] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [[Cl(2)(tBuN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (M=Nb (4), Ta (5)), both complexes react with 2,4,6-trimethylaniline to yield the analogous species [[Cl(2)(ArN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (Ar=2,4,6-C(6)H(2)Me(3), M=Nb (6.C(7)H(8)), Ta (7.C(7)H(8))). Also the azaheterodicubanes [M[micro(3)-N)(2)(micro(3)-NH)](2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2C(7)H(8) [M=Ti (8.2C(7)H(8)), Zr (9.2C(7)H(8))], and [M[(micro(3)-N)(5)(micro(3)-NH)][Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2 C(7)H(8) (Nb (10.2C(7)H(8)), Ta (11.2C(7)H(8))) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe(2))(x)] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 degrees C. X-ray crystal structure determinations were performed for 6 and 10, which revealed a cube- and double-cube-type core, respectively. For complexes 2 and 4-7 we observed and studied by DNMR a rotation or trigonal-twist of the organometallic ligands [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) and [(micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]](1-). Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.

Density functional theory calculations have been carried out to explore the effect of hydrogen on the oxidation of CO in relation to the preferential oxidation of CO in the presence of excess hydrogen (PROX). A range of gold surfaces have been selected including the (100), stepped (310) surfaces and diatomic rows on the (100) surface. These diatomic rows on Au(100) are very efficient in H-H bond scission. O(2) hydrogenation strongly enhances the surface-oxygen interaction and assists in scission of the O-O bond. The activation energy required to make the reaction intermediate hydroperoxy (OOH) from O(2) and H is small. However, we postulate its presence on our Au models as the result of diffusion from oxide supports to the gold surfaces. The OOH on Au in turn opens many low energy cost channels to produce H(2)O and CO(2). CO is selectively oxidized in a H(2) atmosphere due to the more favorable reaction barriers while the formation of adsorbed hydroperoxy enhances the reaction rate.

Adsorption energies and vibrational frequencies of CO and NO adsorbed on gold (1 1 1), (1 0 0), (1 1 0) and (3 1 0) surfaces, as well as on adatoms on Au(1 0 0) have been calculated using density functional theory. The results clearly show that the adsorption energy of the molecules increases considerably with increasing the degree of coordinative unsaturation of the gold atoms to which the molecules bind, and thus support the view that defects, steps and kinks on the surface determine the activity of gold catalysts. © 2009 Elsevier B.V. All rights reserved.

The capacity of the imido-nitrido organometallic ligand [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)] (1) to entrap main group metal halides MXn has been investigated. Treatment of 1 with metal halides in toluene or dichloromethane afforded several soluble adducts [MXn(L)] (L=1) in good yields. The reaction of 1 with one equivalent of Group 1 and 13 monohalides MX afforded single cube-type complexes [XM{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (M=Li, X=Br (2), I (3); M=Na, X=I (4); M=In, X=I (5); M=Tl, X=I (6)). Analogous treatment of 1 with Group 2 and 14 dihalides MX(2) gave the corresponding adducts [I2M{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (M=Mg (7), Ca (8), Sr (9)) and [Cl(2)M{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (M=Sn (10), Pb (11)). The treatment of 1 with SnI2 or the reaction of 10 with MeI at 60 degrees C afforded two azametallocubane units linked by two bridging iodine atoms [{ISn(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}2(mu-I)2] (12). Indium triiodide reacted with 1 in toluene to form the adduct [I3In(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)] (13). Density functional theory calculations have been carried out to study these processes and evaluate the influence of the solvent. X-ray crystal structure determinations have been performed for complexes 10, 12, and 13.

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. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 964972 (H2020-FETOPEN-2018-2019-2020-01). C.B., M.F., and J.G. thank the SpinCat consortium and the Ministerio de Ciencia e Innovación (España) to recognize MagnetoCat SL as “Pyme Innovadora”.

We calculate the energetics of CO oxidation on extended surfaces of particular structures chosen to maximize their reactivity towards either O2 dissociation, after which CO + O to CO2 is a facile reaction, or to CO2 from molecular O2 and CO. We identified two configurations of Au atoms for which the energetics of these reactions are feasible. A site consisting of four Au atoms in a square geometry appears well suited for dissociating oxygen. A Au38 cluster exposing this site provides the most favourable energetics for the CO oxidation.

The relationship between magnetism and catalysis has been an important topic since the mid-20th century. At present time, the scientific community is well aware that a full comprehension of this relationship is required to face modern challenges, such as the need for clean energy technology. The successful use of (para-)magnetic materials has already been corroborated in catalytic processes, such as hydrogenation, Fenton reaction and ammonia synthesis. These catalysts typically contain transition metals from the first to the third row and are affected by the presence of an external magnetic field. Nowadays, it appears that the most promising approach to reach the goal of a more sustainable future is via ferromagnetic conducting catalysts containing open-shell metals (i.e., Fe, Co and Ni) with extra stabilization coming from the presence of an external magnetic field. However, understanding how intrinsic and extrinsic magnetic features are related to catalysis is still a complex task, especially when catalytic performances are improved by these magnetic phenomena. In the present review, we introduce the relationship between magnetism and catalysis and outline its importance in the production of clean energy, by describing the representative case of 3d metal Pt-based alloys, which are extensively investigated and exploited in PEM fuel cells.