The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jens K Norskov - One of the best experts on this subject based on the ideXlab platform.
-
electronic origin of the surface reactivity of transition metal doped tio2 110
Journal of Physical Chemistry C, 2013Co-Authors: Monica Garciamota, Frank Abildpedersen, Aleksandra Vojvodic, Jens K NorskovAbstract:We investigate the surface reactivity of doped rutile M-TiO2(110) (M = V, Cr, Mo, W, Mn, Fe, Ru, Co, Ir, and Ni) using density functional theory (DFT) and Hubbard-U corrected DFT calculations (DFT+U method). The oxygen Adsorption bond, used as the surface reactivity measure, is stronger on the doped TiO2 surfaces as compared with that on the undoped TiO2 surface. We relate this increase in reactivity of the doped TiO2 surfaces to the presence of localized surface resonances and surface states in the vicinity of the Fermi level. We find that the center of these localized states on doped TiO2 is a good descriptor for the oxygen Adsorption Energy. The inclusion of the Hubbard-U correction to DFT barely modifies the oxygen Adsorption Energy on undoped TiO2, whereas it destabilizes the oxygen Adsorption energies on doped TiO2 when compared with results from standard DFT. Nevertheless, we find that the oxygen Adsorption Energy trends predicted by a standard GGA-DFT functional are reproduced when the Hubbard-U c...
-
scaling properties of Adsorption energies for hydrogen containing molecules on transition metal surfaces
Physical Review Letters, 2007Co-Authors: Frank Abildpedersen, Thomas Bligaard, Jeffrey Greeley, Felix Studt, Jan Rossmeisl, Ture R Munter, Poul Georg Moses, Egill Skulason, Jens K NorskovAbstract:Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 Adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the Adsorption Energy of any of the molecules considered scales approximately with the Adsorption Energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions.
-
scaling properties of Adsorption energies for hydrogen containing molecules on transition metal surfaces
Physical Review Letters, 2007Co-Authors: Frank Abildpedersen, Thomas Bligaard, Jeffrey Greeley, Felix Studt, Jan Rossmeisl, Ture R Munter, Poul Georg Moses, Egill Skulason, Jens K NorskovAbstract:Density functional theory calculations are presented for CHx, x � 0; 1; 2; 3, NHx, x � 0; 1; 2, OHx, x � 0; 1, and SHx, x � 0; 1 Adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the Adsorption Energy of any of the molecules considered scales approximately with the Adsorption Energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions. The formation of a bond between a molecule and a metal surface is an important phenomenon in a number of processes including heterogeneous catalysis [1], contact formation in molecular electronics [2], and anchoring of biomolecules to solids for sensors and other biomedical applications [3]. The Adsorption Energy is a key quantity describing the strength of the interaction of molecules with the surface. The Adsorption Energy can be measured by advanced surface science techniques [4 –6]. Alternatively, density functional theory (DFT) offers the possibility of calculating Adsorption energies with reasonable accuracy [7–11]. While both experiments and DFT calculations are feasible for a limited number of systems, they can hardly be performed in detail for all potentially interesting Adsorption systems. There is therefore a need for simple models with the ability to estimate bond energies in a first screening of interesting systems. A successful model will also expose the important factors determining the strength of an adsorbate-surface bond. In the present Letter we will develop such a model for hydrogen-containing molecules. We use DFT calculations to derive a number of correlations between Adsorption energies, and we then present a model to explain them. The model shows how the adsorbate valency, together with the properties of the d electrons of the surface, determines the Adsorption Energy. We further develop the scaling model into a method for estimating hydrogenation or dehydrogenation reaction energies for organic molecules on transition-metal surfaces. The model is tested against full DFT calculations for reactions of hydrocarbons, alcohols, thiols, and amino acids. First, we present results of extensive DFT calculations of the Adsorption energies of CHx, x � 0; 1; 2; 3, NHx, x � 0; 1; 2, OHx, x � 0; 1, and SHx, x � 0; 1 on a range of close-packed and stepped metal surfaces. The study involves the close-packed fcc(111), fcc(100), hcp(0001), and bcc(110) surfaces, and the stepped fcc(211) and bcc(210) surfaces. Each of the surfaces is modeled by a (2 � 2 )o r a (1 � 2) surface unit cell for the close-packed and stepped surfaces, respectively. Each slab has a thickness of three layers in the direction perpendicular to the close-packed surface. These slabs are thick enough to capture the trends in the chemisorption energetics. The adsorbates and the topmost layer are allowed to relax fully in all configurations, and in the case of Fe, Ni, and Co, spin polarization is taken into account. The binding energies of the different species have been taken for the most stable Adsorption sites on all surfaces. The RPBE functional [12] in the generalized gradient approximation is used to describe exchange and correlation effects. The calculational method and setup is described in Ref. [13]. Figure 1 summarizes the results of the DFT calculations. We find for all the molecules studied that the Adsorption Energy of molecule AHx is linearly correlated with the Adsorption Energy of atom A:
Federico Callevallejo - One of the best experts on this subject based on the ideXlab platform.
-
does the breaking of Adsorption Energy scaling relations guarantee enhanced electrocatalysis
Current Opinion in Electrochemistry, 2018Co-Authors: Nitish Govindarajan, J M Garcialastra, Evert Jan Meijer, Federico CallevallejoAbstract:The Adsorption energies of numerous species on homogeneous and heterogeneous catalysts scale linearly with each other. Such linear dependence lowers the degrees of freedom in multistep reactions, greatly simplifying computational electrocatalysis models. The downside of scaling relations is that they limit the efficiency of electrocatalytic reactions. For instance, the scaling relation between *OOH vs *OH supposedly limits the oxygen evolution and reduction reactions (OER, ORR): while the energetic separation of these intermediates should ideally be 2.46 eV, on most catalysts it is ∼3.20 eV. Thus, it is currently assumed that breaking such scaling relation might lead to significant enhancement of OER/ORR electrocatalysis. In this review, we evaluate this hypothesis using literature data. The analysis suggests that breaking the *OOH vs *OH scaling relation is a necessary yet insufficient condition to optimize OER/ORR electrocatalysts. Alternatively, we define a new descriptor: the electrochemical-step symmetry index (ESSI), the optimization of which effectively corresponds to low calculated overpotentials.
-
how covalence breaks Adsorption Energy scaling relations and solvation restores them
Chemical Science, 2017Co-Authors: Federico Callevallejo, Alexander Krabbe, J M GarcialastraAbstract:It is known that breaking the scaling relations between the Adsorption energies of *O, *OH, and *OOH is paramount in catalyzing more efficiently the reduction of O2 in fuel cells and its evolution in electrolyzers. Taking metalloporphyrins as a case study, we evaluate here the Adsorption energies of those adsorbates on the metal centers Cr, Mn, Fe, Co, Ni and Cu, using H, F, OH, NH2, CH3, and BH2 as ring ligands. We show that covalence systematically breaks scaling relations under vacuum by strengthening certain M–OOH bonds. However, covalence modifies adsorbate solvation in solution depending on the degree of covalence of the metal–adsorbate bonds. The two effects have similar magnitudes and opposite signs, such that scaling relations are restored in solution. Thus, solvation is a crucial ingredient that must be taken into account in studies aimed at breaking scaling relations in solution. Our findings suggest that the choice of metal and ligand determines the catalytic activity within the limits imposed by scaling relations, whereas the choice of an appropriate solvent can drive such activity beyond those limits.
-
introducing structural sensitivity into Adsorption Energy scaling relations by means of coordination numbers
Nature Chemistry, 2015Co-Authors: Federico Callevallejo, Marc T M Koper, David Loffreda, Philippe SautetAbstract:The search for improved heterogeneous catalysts is an important but difficult task. Scaling relations between the Adsorption energies of reaction intermediates greatly facilitate the computational design of catalysts. However, this methodology does not currently incorporate structure sensitivity and hence cannot describe adequately the overall activity of realistic catalyst particles and extended surfaces with several facets, edges and apices. Here, we generalize scaling relations by examining twelve different low-index, stepped and kinked surfaces of nine transition metals. This allows us to quantify the effect of the Adsorption-site geometry on these relations, ensures a full prediction of their parameters, and helps in identifying intrinsic thermodynamic restrictions to the performance of catalysts. The resulting fully predictable, structure-sensitive scaling relations are a step towards the long-sought rational design of multifaceted catalytic particles. Such a design can now target not only the chemical nature of active materials but also the actual geometry of their active sites.
-
number of outer electrons as descriptor for Adsorption processes on transition metals and their oxides
Chemical Science, 2013Co-Authors: Federico Callevallejo, Nilay Inoglu, Haiyan Su, Jose I Martinez, Marc T M Koper, John R Kitchin, Jan RossmeislAbstract:The trends in Adsorption energies of the intermediates of the oxygen reduction and evolution reactions on transition metals and their oxides are smoothly captured by the number of outer electrons. This unique descriptor permits the construction of predictive Adsorption-Energy grids and explains the existence of scaling relationships among these compounds.
Frank Abildpedersen - One of the best experts on this subject based on the ideXlab platform.
-
electronic origin of the surface reactivity of transition metal doped tio2 110
Journal of Physical Chemistry C, 2013Co-Authors: Monica Garciamota, Frank Abildpedersen, Aleksandra Vojvodic, Jens K NorskovAbstract:We investigate the surface reactivity of doped rutile M-TiO2(110) (M = V, Cr, Mo, W, Mn, Fe, Ru, Co, Ir, and Ni) using density functional theory (DFT) and Hubbard-U corrected DFT calculations (DFT+U method). The oxygen Adsorption bond, used as the surface reactivity measure, is stronger on the doped TiO2 surfaces as compared with that on the undoped TiO2 surface. We relate this increase in reactivity of the doped TiO2 surfaces to the presence of localized surface resonances and surface states in the vicinity of the Fermi level. We find that the center of these localized states on doped TiO2 is a good descriptor for the oxygen Adsorption Energy. The inclusion of the Hubbard-U correction to DFT barely modifies the oxygen Adsorption Energy on undoped TiO2, whereas it destabilizes the oxygen Adsorption energies on doped TiO2 when compared with results from standard DFT. Nevertheless, we find that the oxygen Adsorption Energy trends predicted by a standard GGA-DFT functional are reproduced when the Hubbard-U c...
-
scaling properties of Adsorption energies for hydrogen containing molecules on transition metal surfaces
Physical Review Letters, 2007Co-Authors: Frank Abildpedersen, Thomas Bligaard, Jeffrey Greeley, Felix Studt, Jan Rossmeisl, Ture R Munter, Poul Georg Moses, Egill Skulason, Jens K NorskovAbstract:Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 Adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the Adsorption Energy of any of the molecules considered scales approximately with the Adsorption Energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions.
-
scaling properties of Adsorption energies for hydrogen containing molecules on transition metal surfaces
Physical Review Letters, 2007Co-Authors: Frank Abildpedersen, Thomas Bligaard, Jeffrey Greeley, Felix Studt, Jan Rossmeisl, Ture R Munter, Poul Georg Moses, Egill Skulason, Jens K NorskovAbstract:Density functional theory calculations are presented for CHx, x � 0; 1; 2; 3, NHx, x � 0; 1; 2, OHx, x � 0; 1, and SHx, x � 0; 1 Adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the Adsorption Energy of any of the molecules considered scales approximately with the Adsorption Energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions. The formation of a bond between a molecule and a metal surface is an important phenomenon in a number of processes including heterogeneous catalysis [1], contact formation in molecular electronics [2], and anchoring of biomolecules to solids for sensors and other biomedical applications [3]. The Adsorption Energy is a key quantity describing the strength of the interaction of molecules with the surface. The Adsorption Energy can be measured by advanced surface science techniques [4 –6]. Alternatively, density functional theory (DFT) offers the possibility of calculating Adsorption energies with reasonable accuracy [7–11]. While both experiments and DFT calculations are feasible for a limited number of systems, they can hardly be performed in detail for all potentially interesting Adsorption systems. There is therefore a need for simple models with the ability to estimate bond energies in a first screening of interesting systems. A successful model will also expose the important factors determining the strength of an adsorbate-surface bond. In the present Letter we will develop such a model for hydrogen-containing molecules. We use DFT calculations to derive a number of correlations between Adsorption energies, and we then present a model to explain them. The model shows how the adsorbate valency, together with the properties of the d electrons of the surface, determines the Adsorption Energy. We further develop the scaling model into a method for estimating hydrogenation or dehydrogenation reaction energies for organic molecules on transition-metal surfaces. The model is tested against full DFT calculations for reactions of hydrocarbons, alcohols, thiols, and amino acids. First, we present results of extensive DFT calculations of the Adsorption energies of CHx, x � 0; 1; 2; 3, NHx, x � 0; 1; 2, OHx, x � 0; 1, and SHx, x � 0; 1 on a range of close-packed and stepped metal surfaces. The study involves the close-packed fcc(111), fcc(100), hcp(0001), and bcc(110) surfaces, and the stepped fcc(211) and bcc(210) surfaces. Each of the surfaces is modeled by a (2 � 2 )o r a (1 � 2) surface unit cell for the close-packed and stepped surfaces, respectively. Each slab has a thickness of three layers in the direction perpendicular to the close-packed surface. These slabs are thick enough to capture the trends in the chemisorption energetics. The adsorbates and the topmost layer are allowed to relax fully in all configurations, and in the case of Fe, Ni, and Co, spin polarization is taken into account. The binding energies of the different species have been taken for the most stable Adsorption sites on all surfaces. The RPBE functional [12] in the generalized gradient approximation is used to describe exchange and correlation effects. The calculational method and setup is described in Ref. [13]. Figure 1 summarizes the results of the DFT calculations. We find for all the molecules studied that the Adsorption Energy of molecule AHx is linearly correlated with the Adsorption Energy of atom A:
Jan Rossmeisl - One of the best experts on this subject based on the ideXlab platform.
-
number of outer electrons as descriptor for Adsorption processes on transition metals and their oxides
Chemical Science, 2013Co-Authors: Federico Callevallejo, Nilay Inoglu, Haiyan Su, Jose I Martinez, Marc T M Koper, John R Kitchin, Jan RossmeislAbstract:The trends in Adsorption energies of the intermediates of the oxygen reduction and evolution reactions on transition metals and their oxides are smoothly captured by the number of outer electrons. This unique descriptor permits the construction of predictive Adsorption-Energy grids and explains the existence of scaling relationships among these compounds.
-
scaling properties of Adsorption energies for hydrogen containing molecules on transition metal surfaces
Physical Review Letters, 2007Co-Authors: Frank Abildpedersen, Thomas Bligaard, Jeffrey Greeley, Felix Studt, Jan Rossmeisl, Ture R Munter, Poul Georg Moses, Egill Skulason, Jens K NorskovAbstract:Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 Adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the Adsorption Energy of any of the molecules considered scales approximately with the Adsorption Energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions.
-
scaling properties of Adsorption energies for hydrogen containing molecules on transition metal surfaces
Physical Review Letters, 2007Co-Authors: Frank Abildpedersen, Thomas Bligaard, Jeffrey Greeley, Felix Studt, Jan Rossmeisl, Ture R Munter, Poul Georg Moses, Egill Skulason, Jens K NorskovAbstract:Density functional theory calculations are presented for CHx, x � 0; 1; 2; 3, NHx, x � 0; 1; 2, OHx, x � 0; 1, and SHx, x � 0; 1 Adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the Adsorption Energy of any of the molecules considered scales approximately with the Adsorption Energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions. The formation of a bond between a molecule and a metal surface is an important phenomenon in a number of processes including heterogeneous catalysis [1], contact formation in molecular electronics [2], and anchoring of biomolecules to solids for sensors and other biomedical applications [3]. The Adsorption Energy is a key quantity describing the strength of the interaction of molecules with the surface. The Adsorption Energy can be measured by advanced surface science techniques [4 –6]. Alternatively, density functional theory (DFT) offers the possibility of calculating Adsorption energies with reasonable accuracy [7–11]. While both experiments and DFT calculations are feasible for a limited number of systems, they can hardly be performed in detail for all potentially interesting Adsorption systems. There is therefore a need for simple models with the ability to estimate bond energies in a first screening of interesting systems. A successful model will also expose the important factors determining the strength of an adsorbate-surface bond. In the present Letter we will develop such a model for hydrogen-containing molecules. We use DFT calculations to derive a number of correlations between Adsorption energies, and we then present a model to explain them. The model shows how the adsorbate valency, together with the properties of the d electrons of the surface, determines the Adsorption Energy. We further develop the scaling model into a method for estimating hydrogenation or dehydrogenation reaction energies for organic molecules on transition-metal surfaces. The model is tested against full DFT calculations for reactions of hydrocarbons, alcohols, thiols, and amino acids. First, we present results of extensive DFT calculations of the Adsorption energies of CHx, x � 0; 1; 2; 3, NHx, x � 0; 1; 2, OHx, x � 0; 1, and SHx, x � 0; 1 on a range of close-packed and stepped metal surfaces. The study involves the close-packed fcc(111), fcc(100), hcp(0001), and bcc(110) surfaces, and the stepped fcc(211) and bcc(210) surfaces. Each of the surfaces is modeled by a (2 � 2 )o r a (1 � 2) surface unit cell for the close-packed and stepped surfaces, respectively. Each slab has a thickness of three layers in the direction perpendicular to the close-packed surface. These slabs are thick enough to capture the trends in the chemisorption energetics. The adsorbates and the topmost layer are allowed to relax fully in all configurations, and in the case of Fe, Ni, and Co, spin polarization is taken into account. The binding energies of the different species have been taken for the most stable Adsorption sites on all surfaces. The RPBE functional [12] in the generalized gradient approximation is used to describe exchange and correlation effects. The calculational method and setup is described in Ref. [13]. Figure 1 summarizes the results of the DFT calculations. We find for all the molecules studied that the Adsorption Energy of molecule AHx is linearly correlated with the Adsorption Energy of atom A:
Jing Liu - One of the best experts on this subject based on the ideXlab platform.
-
interfacial wetting behaviors of liquid ga alloys fega3 based on metallic bond interaction
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Yuntao Cui, Fei Liang, Yujie Ding, Zheshuai Lin, Jing LiuAbstract:Abstract This work presents a peculiar metallic bond interaction which strongly improves wetting performance and Adsorption Energy at the liquid Ga/FeGa3 interfaces and gets stronger with the increasing content of gallium. To quantitatively evaluate the interfacial wetting phenomenon, an interfacial wetting model based on the metallic bond interaction is built and investigated. The underlying mechanism attributes to the intermetallic FeGa3 formed and covering on the Fe substrate surface, which forms the strong metallic bond interaction with Ga atoms to bring about an excellent wetting performance. Based on the first principles calculations and simulations, comparable electrostatic potentials of Ga atom on FeGa3(010) disclose the valence electrons can exchange easily between liquid Ga atom and the Fe-Ga interlayers of FeGa3, thus leading to valence electron hybridization. The calculation results for the density of states (DOS) exhibit that the peaks of valence electron hybridization emerged between Ga and FeGa3(010), which results in the metallic bond interaction. Moreover, the experimental findings and the predicted data show that the metallic bond interaction has been confirmed to be accordant with the interfacial wetting behavior and Adsorption Energy of liquid Ga alloys (LGAs) on the FeGa3 slab.
-
Metallic Bond-Enabled Wetting Behavior at the Liquid Ga/CuGa2 Interfaces
2018Co-Authors: Yuntao Cui, Fei Liang, Yujie Ding, Zheshuai Lin, Zhenze Yang, Xi Zhao, Jing LiuAbstract:Interface interaction can strongly modify contact angle, Adsorption Energy, interfacial tension, and composition of the contact area. In particular, the interfaces between gallium-based liquid metal (LM) and its intermetallic layer present many mysterious and peculiar wetting phenomena, which have not been fully realized up to now. Here in this study, we found that a gallium-based liquid metal droplet can quickly transform into a puddle on the CuGa2 surface through a spreading–wetting procedure. The mechanism lying behind this phenomenon can be ascribed to the formation of an intermetallic CuGa2 on Cu plate surface, which provides a stable metallic bond to induce the wetting behavior. For a quantitative evaluation of the interface force, a metallic bond-enabled wetting model is established on the basis of the density functional theory. The first-principles density functional calculations are then performed to examine the work function, density of states, and Adsorption Energy. The predicted results show that the work function of CuGa2 (010) is approximately 4.47 eV, which is very comparable with that of pure liquid Ga (4.32 eV). This indicates that the valence electrons between Ga and CuGa2 slab can exchange easily, which consequently leads to the strong valence electron hybridization and metallic bond. In addition, the Adsorption Energy of a single Ga atom on CuGa2 (010) slab has a larger value than In and Sn. The tested metallic bond wetting force at the interface is proportional to the average Adsorption Energy of the gallium-based LM adatom, and increases with the rising content of gallium. The simulation results demonstrate excellent consistency with the experimental data in this work