We analyse the transition state energies for 249 hydrogenation/dehydrogenation reactions of atoms and simple molecules over close-packed and stepped surfaces and nanoparticles of transition metals using Density Functional Theory. Linear energy scaling relations are observed for the transition state structures leading to transition state scaling relations for all the investigated reactions. With a suitable choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters.

There has been substantial progress in the description of adsorption and chemical reactions of simple molecules on transition-metal surfaces. Adsorption energies and activation energies have been obtained for a number of systems, and complete catalytic reactions have been described in some detail. [1][2][3][4][5][6][7] Considerable progress has also been made in the theoretical description of the interaction of molecules with transition-metal oxides, [8][9][10][11][12][13][14][15][16][17][18][19] sulfides, [20][21][22][23][24][25] and nitrides, [26][27][28][29] but it is considerably more complicated to describe such complex systems theoretically. Complications arise from difficulties in describing the stoichiometry and structure of such surfaces, and from possible shortcomings in the use of ordinary generalized gradient approximation (GGA) type density functional theory (DFT).[30]Herein we introduce a method that may facilitate the description of the bonding of gas molecules to transitionmetal oxides, sulfides, and nitrides. It was recently found that there are a set of scaling relationhips between the adsorption energies of different partially hydrogenated intermediates on transition-metal surfaces.[31] We will show that similar scaling relationships exist for adsorption on transition metal oxide, sulfide, and nitride surfaces. This means that knowing the adsorption energy for one transition-metal complex will make it possible to quite easily generate data for a number of other complexes, and in this way obtain reactivity trends.The results presented herein have been calculated using self-consistent DFT. Exchange and correlation effects are described using the revised Perdew-Burke-Ernzerhof (RPBE) [32] GGA functional. It is known that GGA functionals give adsorption energies with reasonable accuracy for transition metals. [32,33] It is not clear, however, whether a similar accuracy can be expected for the oxides, sulfides, and nitrides, although there are examples of excellent agreement between DFT calculations and experiments, for example, with RuO 2 surfaces.[9] In our study we focused entirely on variations in the adsorption energies from one system to another, and we expected that such results would be less dependent than the absolute adsorption energies on the description of exchange and correlation.For the nitrides, a clean surface and a surface with a nitrogen vacancy were studied. For MX 2 -type oxides or sulfides, an oxygen-or sulfur-covered surface with an oxygen or sulfur vacancy was studied. The structures of the clean surface considered in the present work and their unit cells are shown in Figure 1. The adsorption energies given below are for the adsorbed species in the most stable adsorption site on the surface.By performing calculations for a large number of transition-metal surfaces of different orientations, [31] it was found that the adsorption energy of intermediates of the type AH x is linearly correlated with the adsorption energy of atom A (N, O, S) according to Equation (1):Here the scali...

Versatile Brønsted-Evans-Polanyi (BEP) relations are found from density functional theory for a wide range of transition metal oxides including rutiles and perovskites. For oxides, the relation depends on the type of oxide, the active site and the dissociating molecule. The slope of the BEP relation is strongly coupled to the adsorbate geometry in the transition state. If it is final state-like the dissociative chemisorption energy can be considered as a descriptor for the dissociation. If it is initial state-like, on the other hand, the dissociative chemisorption energy is not suitable as descriptor for the dissociation. Dissociation of molecules with strong intramolecular bonds belong to the former and molecules with weak intramolecular bonds to the latter group. We show, for the prototype system La-perovskites, that there is a "cyclic" behavior in the transition state characteristics upon change of the active transition metal of the oxide.

There has been substantial progress in the description of adsorption and chemical reactions of simple molecules on transition-metal surfaces. Adsorption energies and activation energies have been obtained for a number of systems, and complete catalytic reactions have been described in some detail. [1][2][3][4][5][6][7] Considerable progress has also been made in the theoretical description of the interaction of molecules with transition-metal oxides, [8][9][10][11][12][13][14][15][16][17][18][19] sulfides, [20][21][22][23][24][25] and nitrides, [26][27][28][29] but it is considerably more complicated to describe such complex systems theoretically. Complications arise from difficulties in describing the stoichiometry and structure of such surfaces, and from possible shortcomings in the use of ordinary generalized gradient approximation (GGA) type density functional theory (DFT).[30]Herein we introduce a method that may facilitate the description of the bonding of gas molecules to transitionmetal oxides, sulfides, and nitrides. It was recently found that there are a set of scaling relationhips between the adsorption energies of different partially hydrogenated intermediates on transition-metal surfaces.[31] We will show that similar scaling relationships exist for adsorption on transition metal oxide, sulfide, and nitride surfaces. This means that knowing the adsorption energy for one transition-metal complex will make it possible to quite easily generate data for a number of other complexes, and in this way obtain reactivity trends.The results presented herein have been calculated using self-consistent DFT. Exchange and correlation effects are described using the revised Perdew-Burke-Ernzerhof (RPBE) [32] GGA functional. It is known that GGA functionals give adsorption energies with reasonable accuracy for transition metals. [32,33] It is not clear, however, whether a similar accuracy can be expected for the oxides, sulfides, and nitrides, although there are examples of excellent agreement between DFT calculations and experiments, for example, with RuO 2 surfaces.[9] In our study we focused entirely on variations in the adsorption energies from one system to another, and we expected that such results would be less dependent than the absolute adsorption energies on the description of exchange and correlation.For the nitrides, a clean surface and a surface with a nitrogen vacancy were studied. For MX 2 -type oxides or sulfides, an oxygen-or sulfur-covered surface with an oxygen or sulfur vacancy was studied. The structures of the clean surface considered in the present work and their unit cells are shown in Figure 1. The adsorption energies given below are for the adsorbed species in the most stable adsorption site on the surface.By performing calculations for a large number of transition-metal surfaces of different orientations, [31] it was found that the adsorption energy of intermediates of the type AH x is linearly correlated with the adsorption energy of atom A (N, O, S) according to Equation (1):Here the scali...

We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K ͑M 1 ͒; and 1 alkali, alkaline earth or 3d / 4d transition metal atom ͑M 2 ͒ plus two to five ͑BH 4 ͒ − groups, i.e., M 1 M 2 ͑BH 4 ͒ 2-5 , using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M 1 ͑Al/ Mn/ Fe͒͑BH 4 ͒ 4 , ͑Li/ Na͒Zn͑BH 4 ͒ 3 , and ͑Na/ K͒͑Ni/ Co͒͑BH 4 ͒ 3 alloys are found to be the most promising, followed by selected M 1 ͑Nb/ Rh͒͑BH 4 ͒ 4 alloys.

We investigate the heterogeneously catalysed oxidation of HX (X=Cl, Br and I) on the RuO2 (1 1 0) surface with DFT. We also solve a micro‐kinetic model of HX oxidation and compare oxidation activity at different coverages. We further establish linear energy relations for the reaction intermediates over a range of different rutile oxide surfaces. Based on the scaling relations, two descriptors are identified that describe the reactions uniquely. By combining scaling with the micro‐kinetic model, activity volcanoes for the three different oxidation reactions are derived. It is found that the commonly used RuO2 catalyst for HCl oxidation is closest to optimal for all three oxidation processes.