Methane activation is one of the most important industrial processes in a modern-day society as it plays a key role in the production of syngas that is used to make a wide spectrum of hydrocarbons and alcohols that sustain the energy and chemical needs of humankind. Using density functional theory calculations, we identified the electronic properties governing the high stability of atomic carbon on stepped Ni surface to address the carbon formation or "coking" reaction that deactivates the catalyst. Results show that atomic carbon adsorption is uniquely characterized by a 5-coordinated bonding with Ni atoms from both the surface and subsurface layers of stepped Ni surface. Interestingly, we found that substituting the specific subsurface Ni atoms with other elements can dramatically change the reaction mechanism of methane decomposition on the surface, suggesting a new approach to catalyst design for hydrocarbon reforming applications. In this proceeding, the other possible models for modifying Ni surface that utilizes this idea are presented.

The adsorption of CO2 on CuO(110) was investigated using density functional theory calculations. The CO2 molecule adsorbs on top of an unsaturated Cu atom with a titled configuration. The low adsorption energy and minimal charge transfer confirm the physisorption character of the adsorption process. Unlike pure copper, the more reactive behavior towards CO2 of copper oxides makes them useful for applications such as the photocatalytic reduction of CO2.

First-principles density functional theory calculations were performed to study the adsorption of borohydride (BH(4)(-)) on close-packed transition-metal surfaces, M(111) (M = Au, Pt, Ir, Os, Ag, Pd, Rh, Ru). A correlation between the relative adsorption energies of BH(4ad) and the d-band center of the metals is established. In terms of the adsorbate configuration, both molecular (BH(4ad)) and dissociated (BH(4y,ad) + yH(ad), y = 1,...,3) structures are possible regardless of the adsorption energy value. On Os, Rh, and Ru surfaces, molecular (i.e., undissociative) adsorption is preferred despite the strong surface binding energy of BH(4ad). Orbital-specific analysis of the bonding, points to the role of the d(zz) and d(yz) states of the surface metal atoms in determining the final BH(4ad) configuration on all metals. However, in the presence of H(2)O molecules, the preference for strong molecular adsorption may be lost because of BH(4ad)-H(2)O(ad) interaction. Using the coadsorption on Os(111) of BH(4ad) and H(2)O(ad) with and without the presence of Had (generated either by electrosorption of OH(-) or dissociative water adsorption), the origins of the adsorbate adsorbate and adsorbate metal interactions are discussed. Electronic factors to predict the BH(4ad) conformation on metal catalysts in water environment are proposed.

Elucidating the reaction mechanism of steam methane reforming (SMR) is imperative for the rational design of catalysts for efficient hydrogen production. In this paper, we provide mechanistic insights into SMR on Ru surface using first principles calculations based on dispersion-corrected density functional theory. Methane activation (i. e., C-H bond cleavage) was found to proceed via a thermodynamically exothermic dissociative adsorption process, resulting in (CHy + zH)* species ("*" denotes a surface-bound state, and y + z =3D 4), with C* and CH* being the most stable adsorbates. The calculation of activation barriers suggests that the conversion of C* into O-containing species via C-O bond formation is kinetically slow, indicating that the surface reaction of carbon intermediates with oxygen is a possible rate-determining step. The results suggest the importance of subsequent elementary reactions following methane activation in determining the formation of stable carbon structures on the surface that deactivates the catalyst or the conversion of carbon into O-containing species.

With the aid of density functional theory-based first principles calculations, we investigated energetics and electronic structure changes in reactions involving dopaquinone to give insights into the branching behaviors in melanogenesis. The reactions we investigated are the intramolecular cyclization and thiol binding, which are competing with each other. It was found that, in order to accomplish thiol binding, charge transfer of around one electron from thiol to dopaquinone occurs. Furthermore, intramolecular cyclization of dopaquinone increases the lowest unnoccupied molecular orbital level substantially. This result clearly shows prevention of the binding of thiol by intramolecular cyclization.

The adsorption of borohydride on 3d transition metals (Cr, Mn, Fe, Co, Ni and Cu) was studied using first principles calculations within spin-polarized density functional theory. Magnetic effect on the stability of borohydride is noted. Molecular adsorption is favorable on Co, Ni and Cu, which is characterized by the strong s-d(zz) hybridization of the adsorbate-substrate states. Dissociated adsorption structure yielding one or two H adatom fragments on the surface is observed for Cr, Mn and Fe. (c) 2012 Elsevier B.V. All rights reserved.

We compare the electronic properties of Cu(111) and Cu2O(111) surfaces in relation to the dissociation of NO using first principles calculations within density functional theory. We note a well-defined three-fold site on both O- and Cu-terminated Cu2O surfaces which is verified as the active site for the adsorption and dissociation of NO. The interaction of Cu with O atoms results in the forward shifting of the local density of states and formation of unoccupied states above the Fermi level, compared to the fully occupied d band of pure Cu. These results give valuable insights in the realization of a catalyst without precious metal for the dissociation of NO.

The decomposition of methane (CH4) is a catalytically important reaction in the production of syngas that is used to make a wide spectrum of hydrocarbons and alcohols, and a principal carbon deposition pathway in methane reforming. Literatures suggest that stepped Ni surface is uniquely selective toward methane decomposition to atomic C, contrary to other catalysts that favor the CH fragment. In this paper, we used dispersion-corrected density functional theory-based first principles calculations to identify the electronic factors that govern this interesting property of stepped Ni surface. We found that the adsorption of atomic C on this surface is uniquely characterized by a 5-coordinated bonding of C with Ni atoms from both the surface and subsurface layers. Comparison with Ru surface indicates the importance of the subsurface atoms of stepped Ni surface on its selectivity toward methane decomposition to atomic C. Interestingly, we found that substituting these subsurface atoms with other elements can dramatically change the reaction mechanism of methane decomposition, suggesting a new approach to catalyst design for hydrocarbon reforming applications.