The surface of supported heterogeneous catalysts often contains adsorbed water and hydroxyl groups even when water is not directly added to the reaction stream. Nonetheless, the reactivity of adsorbed water and hydroxyl groups is rarely considered. We demonstrate that water and hydroxyl groups can not only directly participate in the catalytic oxidation processes but are also able to generate and stabilize the catalytically active metal-oxide interface. We show that the reduction of Pt-Fe-supported catalysts with hydrogen in the presence of adsorbed water or steam allows for achieving one of the highest preferential carbon monoxide oxidation activities at ambient temperature. These conditions create active iron-associated hydroxyl groups next to platinum nanoparticles with enhanced reactivity towards carbon monoxide oxidation. Density functional theory calculations suggest that hydroxylation of oxidic iron species stabilizes the FeOx(OH)y/Pt interface, via strong metal-support interaction, which is confirmed by chemisorption measurements. Kinetic experiments, including those with 18O-labeled water, in combination with operando infrared spectroscopy, show that water and hydroxyl groups directly participate in preferential carbon monoxide oxidation. A quantitative correlation between the catalytic activity of Pt-FeOx(OH)y/γ-Al2O3 catalysts and the Fe2+ concentration, obtained using operando X-ray absorption spectroscopy, shows that the number of active Fe2+ sites and the carbon monoxide oxidation rate per active site can be significantly increased by water-assisted pretreatment with hydrogen. This work provides a new example of positive role of strong metal-support interaction for the design of more active catalysts.@en

The direct conversion of methane to methanol using oxygen is a challenging but potentially rewarding pathway towards utilizing methane. By using a stepwise chemical looping approach, copper-exchanged zeolites can convert methane to methanol, but productivity is still too low for viable implementation. However, if the nature of the active site could be elucidated, that information could be used to design more effective catalysts. By employing anomalous X-ray powder diffraction with support from theory and other X-ray techniques, we have derived a quantitative and spatial description of the highly selective, active copper sites in zeolite omega (Cu-omega). This is the first comprehensive description of the structure of non-copper-oxo active species and will provide a pivotal model for future development for materials for methane to methanol conversion.@en

The direct conversion of methane to methanol using oxygen is a challenging but potentially rewarding pathway towards utilizing methane. By using a stepwise chemical looping approach, copper-exchanged zeolites can convert methane to methanol, but productivity is still too low for viable implementation. However, if the nature of the active site could be elucidated, that information could be used to design more effective catalysts. By employing anomalous X-ray powder diffraction with support from theory and other X-ray techniques, we have derived a quantitative and spatial description of the highly selective, active copper sites in zeolite omega (Cu-omega). This is the first comprehensive description of the structure of non-copper-oxo active species and will provide a pivotal model for future development for materials for methane to methanol conversion.@en

The direct conversion of methane to methanol using oxygen is a challenging but potentially rewarding pathway towards utilizing methane. By using a stepwise chemical looping approach, copper-exchanged zeolites can convert methane to methanol, but productivity is still too low for viable implementation. However, if the nature of the active site could be elucidated, that information could be used to design more effective catalysts. By employing anomalous X-ray powder diffraction with support from theory and other X-ray techniques, we have derived a quantitative and spatial description of the highly selective, active copper sites in zeolite omega (Cu-omega). This is the first comprehensive description of the structure of non-copper-oxo active species and will provide a pivotal model for future development for materials for methane to methanol conversion.@en

The direct conversion of methane to methanol using oxygen is a challenging but potentially rewarding pathway towards utilizing methane. By using a stepwise chemical looping approach, copper-exchanged zeolites can convert methane to methanol, but productivity is still too low for viable implementation. However, if the nature of the active site could be elucidated, that information could be used to design more effective catalysts. By employing anomalous X-ray powder diffraction with support from theory and other X-ray techniques, we have derived a quantitative and spatial description of the highly selective, active copper sites in zeolite omega (Cu-omega). This is the first comprehensive description of the structure of non-copper-oxo active species and will provide a pivotal model for future development for materials for methane to methanol conversion.@en

Density-functional theory based global geometry optimization is used to scrutinize the possibility of using endohedrally doped hydrogenated Si clusters as building blocks for constructing highly magnetic materials. In contrast to the known clathrate-type facet-sharing, the clusters exhibit a predisposition to aggregation through double Si-Si bridge bonds. For the prototypical CrSi 20H20 cluster we show that reducing the degree of hydrogenation may be used to control the number of reactive sites to which other cages can be attached, while still preserving the structural integrity of the building block itself. This leads to a toolbox of CrSi20H 20-2n monomers with different number of double "docking sites", that allows building network architectures of any morphology. For (CrSi20H18)2 dimer and [CrSi20H 16](CrSi20H18)2 trimer structures we illustrate that such aggregates conserve the high spin moments of the dopant atoms and are therefore most attractive candidates for cluster-assembled materials with unique magnetic properties. The study suggests that the structural completion of the individual endohedral cages within the doubly bridge bonded structures and the high thermodynamic stability of the obtained aggregates are crucial for potential synthetic polimerization routes via controlled dehydrogenation.@en

Density-functional theory based global geometry optimization is used to scrutinize the possibility of using endohedrally doped hydrogenated Si clusters as building blocks for constructing highly magnetic materials. In contrast to the known clathrate-type facet-sharing, the clusters exhibit a predisposition to aggregation through double Si-Si bridge bonds. For the prototypical CrSi 20H20 cluster we show that reducing the degree of hydrogenation may be used to control the number of reactive sites to which other cages can be attached, while still preserving the structural integrity of the building block itself. This leads to a toolbox of CrSi20H 20-2n monomers with different number of double "docking sites", that allows building network architectures of any morphology. For (CrSi20H18)2 dimer and [CrSi20H 16](CrSi20H18)2 trimer structures we illustrate that such aggregates conserve the high spin moments of the dopant atoms and are therefore most attractive candidates for cluster-assembled materials with unique magnetic properties. The study suggests that the structural completion of the individual endohedral cages within the doubly bridge bonded structures and the high thermodynamic stability of the obtained aggregates are crucial for potential synthetic polimerization routes via controlled dehydrogenation.@en

Fourier transform infrared spectroscopy and density functional theory calculations have been used to elucidate the nature of active sites of ZrBEA zeolite responsible for the catalytic synthesis of butadiene. We show that the content of open Zr(IV) Lewis acid sites, represented by isolated Zr atoms in tetrahedral positions of the zeolite crystalline structure connected to three -O-Si linkages and one OH group, correlates with the catalytic activity in the process of conversion of ethanol into butadiene. The higher catalytic activity of the open sites is attributed to their higher acid strength and steric accessibility. The study suggests that the control of such open sites plays a crucial role for the further design of the optimal multifunctional zeolite-based catalysts. (Figure Presented).@en

Fourier transform infrared spectroscopy and density functional theory calculations have been used to elucidate the nature of active sites of ZrBEA zeolite responsible for the catalytic synthesis of butadiene. We show that the content of open Zr(IV) Lewis acid sites, represented by isolated Zr atoms in tetrahedral positions of the zeolite crystalline structure connected to three -O-Si linkages and one OH group, correlates with the catalytic activity in the process of conversion of ethanol into butadiene. The higher catalytic activity of the open sites is attributed to their higher acid strength and steric accessibility. The study suggests that the control of such open sites plays a crucial role for the further design of the optimal multifunctional zeolite-based catalysts. (Figure Presented).@en

Fourier transform infrared spectroscopy and density functional theory calculations have been used to elucidate the nature of active sites of ZrBEA zeolite responsible for the catalytic synthesis of butadiene. We show that the content of open Zr(IV) Lewis acid sites, represented by isolated Zr atoms in tetrahedral positions of the zeolite crystalline structure connected to three -O-Si linkages and one OH group, correlates with the catalytic activity in the process of conversion of ethanol into butadiene. The higher catalytic activity of the open sites is attributed to their higher acid strength and steric accessibility. The study suggests that the control of such open sites plays a crucial role for the further design of the optimal multifunctional zeolite-based catalysts. (Figure Presented).@en

In this critical review we examine the current state of our knowledge in respect of the nature of the active sites in copper containing zeolites for the selective conversion of methane to methanol. We consider the varied experimental evidence arising from the application of X-ray diffraction, and vibrational, electronic, and X-ray spectroscopies that exist, along with the results of theory. We aim to establish both what is known regarding these elusive materials and how they function, and also where gaps in our knowledge still exist, and offer suggestions and strategies as to how these might be closed such that the rational design of more effective and efficient materials of this type for the selective conversion of methane might proceed further.@en

The metal-support interaction plays a critical role in heterogeneous catalysis. Under reducing conditions, oxidic supports may interact with supported metal particles, by either forming an oxide overlayer or an alloy. The structure of both the support and the nanoparticle, as well as of the interface itself, changes in response to varying environmental conditions. Here, we present a fullyab initioapproach to predict the structures and energetics of such systems for a range of transition metals (Me = Cu, Ru, Pd, Ag, Rh, Os, Ir, Pt, Au) supported on titania surfaces as a function of gas atmosphere composition. The competing formation of a monolayer comprising fully oxidized titania (TiO2), its reduced forms (Ti2O3, TiO), and the Ti-Me surface alloy, is investigated. The stability of each of these phases is found to be very sensitive to the environmental conditions and the supported metal. Encapsulation of metal, also known as classical strong metal-support interaction (SMSI), was predicted by thermodynamic driving force analysis. We show that a simple parameter, the Ti-Me alloy formation energy, is a good descriptor for the strength of the interaction between metal substrates and reduced titania monolayers and has predictive power towards the conditions under which an overlayer is stable. The presented thermochemical data and phase diagram analysis can be used to identify the structure and stability of supported metal catalysts under realistic conditions.@en

Ostwald ripening is a leading cause of the degradation of platinum group catalysts at high temperature in an oxidizing atmosphere. Recent experiments suggested that volatile species can be trapped on ceria, forming atomically dispersed active catalytic sites instead of large nanoparticles. Here we present a comparative density functional theory study of the interaction of PtO2(g), the most likely volatile species responsible for the process of Ostwald ripening, with various surfaces. Defect-free CeO2(111) and Al2O3(100) surfaces have a very small binding energy towards PtO2(g) compared to the platinum surface, indicative of particle growth. However, the stepped edge of the CeO2(111) surface effectively traps the mobile species, generating atomically dispersed catalysts. Such trapped single-atom platinum-on-ceria catalysts are predicted to have a square-planar [PtO4] structure, with the platinum atom strongly binding to the surface, preventing platinum atoms from aggregating into larger nanoparticles. These results provide an atomic insight into the single atom trapping and suggest a route for the development of sinter-resistant catalysts.@en

Ostwald ripening is a leading cause of the degradation of platinum group catalysts at high temperature in an oxidizing atmosphere. Recent experiments suggested that volatile species can be trapped on ceria, forming atomically dispersed active catalytic sites instead of large nanoparticles. Here we present a comparative density functional theory study of the interaction of PtO2(g), the most likely volatile species responsible for the process of Ostwald ripening, with various surfaces. Defect-free CeO2(111) and Al2O3(100) surfaces have a very small binding energy towards PtO2(g) compared to the platinum surface, indicative of particle growth. However, the stepped edge of the CeO2(111) surface effectively traps the mobile species, generating atomically dispersed catalysts. Such trapped single-atom platinum-on-ceria catalysts are predicted to have a square-planar [PtO4] structure, with the platinum atom strongly binding to the surface, preventing platinum atoms from aggregating into larger nanoparticles. These results provide an atomic insight into the single atom trapping and suggest a route for the development of sinter-resistant catalysts.@en

Ostwald ripening is a leading cause of the degradation of platinum group catalysts at high temperature in an oxidizing atmosphere. Recent experiments suggested that volatile species can be trapped on ceria, forming atomically dispersed active catalytic sites instead of large nanoparticles. Here we present a comparative density functional theory study of the interaction of PtO2(g), the most likely volatile species responsible for the process of Ostwald ripening, with various surfaces. Defect-free CeO2(111) and Al2O3(100) surfaces have a very small binding energy towards PtO2(g) compared to the platinum surface, indicative of particle growth. However, the stepped edge of the CeO2(111) surface effectively traps the mobile species, generating atomically dispersed catalysts. Such trapped single-atom platinum-on-ceria catalysts are predicted to have a square-planar [PtO4] structure, with the platinum atom strongly binding to the surface, preventing platinum atoms from aggregating into larger nanoparticles. These results provide an atomic insight into the single atom trapping and suggest a route for the development of sinter-resistant catalysts.@en

Efficient structure search is a major challenge in computational materials science. We present a modification of the basin hopping global geometry optimization approach that uses a curvilinear coordinate system to describe global trial moves. This approach has recently been shown to be efficient in structure determination of clusters [C. Panosetti et al., Nano Lett. 15, 8044-8048 (2015)] and is here extended for its application to covalent, complex molecules and large adsorbates on surfaces. The employed automatically constructed delocalized internal coordinates are similar to molecular vibrations, which enhances the generation of chemically meaningful trial structures. By introducing flexible constraints and local translation and rotation of independent geometrical subunits, we enable the use of this method for molecules adsorbed on surfaces and interfaces. For two test systems, trans-β-ionylideneacetic acid adsorbed on a Au(111) surface and methane adsorbed on a Ag(111) surface, we obtain superior performance of the method compared to standard optimization moves based on Cartesian coordinates.@en

Efficient structure search is a major challenge in computational materials science. We present a modification of the basin hopping global geometry optimization approach that uses a curvilinear coordinate system to describe global trial moves. This approach has recently been shown to be efficient in structure determination of clusters [C. Panosetti et al., Nano Lett. 15, 8044-8048 (2015)] and is here extended for its application to covalent, complex molecules and large adsorbates on surfaces. The employed automatically constructed delocalized internal coordinates are similar to molecular vibrations, which enhances the generation of chemically meaningful trial structures. By introducing flexible constraints and local translation and rotation of independent geometrical subunits, we enable the use of this method for molecules adsorbed on surfaces and interfaces. For two test systems, trans-β-ionylideneacetic acid adsorbed on a Au(111) surface and methane adsorbed on a Ag(111) surface, we obtain superior performance of the method compared to standard optimization moves based on Cartesian coordinates.@en

Efficient structure search is a major challenge in computational materials science. We present a modification of the basin hopping global geometry optimization approach that uses a curvilinear coordinate system to describe global trial moves. This approach has recently been shown to be efficient in structure determination of clusters [C. Panosetti et al., Nano Lett. 15, 8044-8048 (2015)] and is here extended for its application to covalent, complex molecules and large adsorbates on surfaces. The employed automatically constructed delocalized internal coordinates are similar to molecular vibrations, which enhances the generation of chemically meaningful trial structures. By introducing flexible constraints and local translation and rotation of independent geometrical subunits, we enable the use of this method for molecules adsorbed on surfaces and interfaces. For two test systems, trans-β-ionylideneacetic acid adsorbed on a Au(111) surface and methane adsorbed on a Ag(111) surface, we obtain superior performance of the method compared to standard optimization moves based on Cartesian coordinates.@en

Efficient structure search is a major challenge in computational materials science. We present a modification of the basin hopping global geometry optimization approach that uses a curvilinear coordinate system to describe global trial moves. This approach has recently been shown to be efficient in structure determination of clusters [C. Panosetti et al., Nano Lett. 15, 8044-8048 (2015)] and is here extended for its application to covalent, complex molecules and large adsorbates on surfaces. The employed automatically constructed delocalized internal coordinates are similar to molecular vibrations, which enhances the generation of chemically meaningful trial structures. By introducing flexible constraints and local translation and rotation of independent geometrical subunits, we enable the use of this method for molecules adsorbed on surfaces and interfaces. For two test systems, trans-β-ionylideneacetic acid adsorbed on a Au(111) surface and methane adsorbed on a Ag(111) surface, we obtain superior performance of the method compared to standard optimization moves based on Cartesian coordinates.@en

Efficient structure search is a major challenge in computational materials science. We present a modification of the basin hopping global geometry optimization approach that uses a curvilinear coordinate system to describe global trial moves. This approach has recently been shown to be efficient in structure determination of clusters [C. Panosetti et al., Nano Lett. 15, 8044-8048 (2015)] and is here extended for its application to covalent, complex molecules and large adsorbates on surfaces. The employed automatically constructed delocalized internal coordinates are similar to molecular vibrations, which enhances the generation of chemically meaningful trial structures. By introducing flexible constraints and local translation and rotation of independent geometrical subunits, we enable the use of this method for molecules adsorbed on surfaces and interfaces. For two test systems, trans-β-ionylideneacetic acid adsorbed on a Au(111) surface and methane adsorbed on a Ag(111) surface, we obtain superior performance of the method compared to standard optimization moves based on Cartesian coordinates.@en