Surface Structure and Reactivity:  Reactions on Face-Centered Cubic (110) Metal Surfaces Involving Adatom-Induced Reconstructions

Traveling waves and global oscillations triggered by attractive molecular interactions in an excitable system

“…Such an anisotropy in the diffusion coefficients has been shown experimentally in chemical reactions on catalytic surfaces such as Rh(110) [39] and in this case it results from the rectangular symmetry of the surface lattice. For simplicity we assume a constant (i.e., density independent) mobility D. Note that the difference of Eqs.…”

Imaging with Chemical Analysis: Adsorbed Structures Formed during Surface Chemical Reactions

“…Their shape and velocity are controlled by the reaction parameters, that is, pressure and temperature, which in turn control the mobility of the adspecies, their concentration and the substrate surface structure. [17] PEEM, SPEM and LEEM have provided extensive knowledge about the spatiotemporal organisation of adspecies in these simple reaction-diffusion systems. [18][19][20][21][22][23] In these reactions, the reactants adsorb dissociatively on the Rh surface and the interaction between adsorbed H, O and N atoms leads to H 2 O or H 2 O + N 2 products, immediately desorbing in the gas phase.…”

“…In contrast to the water formation reaction, the NO + H 2 reaction on RhA C H T U N G T R E N N U N G (110) displays spatiotemporal oscillations, manifested as alternating reduction and oxidation fronts. The reduction fronts remove the adsorbed oxygen, leading to a local built up of a N adlayer, whereas the oxidation fronts favour nitrogen recombination to N 2 and desorption, because the coadsorbed oxygen destabilises the bonding of adsorbed N. [17] In brief, the propagating reduction and oxidation reaction fronts cause a switching between an O-and N-covered surface regions, the width of the transition zone, in which O and NO are coadsorbed, depending on the reaction parameters. [19,21] The complex chemistry of NO + H 2 reaction, involving the coexistence of O-(1 n) and N-(n 1) reconstructions of the substrate surface with different diffusion anisotropy, [17] leads to a large variety of chemical wave patterns, such as targets and spirals.…”

“…The reduction fronts remove the adsorbed oxygen, leading to a local built up of a N adlayer, whereas the oxidation fronts favour nitrogen recombination to N 2 and desorption, because the coadsorbed oxygen destabilises the bonding of adsorbed N. [17] In brief, the propagating reduction and oxidation reaction fronts cause a switching between an O-and N-covered surface regions, the width of the transition zone, in which O and NO are coadsorbed, depending on the reaction parameters. [19,21] The complex chemistry of NO + H 2 reaction, involving the coexistence of O-(1 n) and N-(n 1) reconstructions of the substrate surface with different diffusion anisotropy, [17] leads to a large variety of chemical wave patterns, such as targets and spirals. [2,18,24] The velocity, shape and wavelength of the reaction-diffusion patterns can be influenced by modifying the structural and chemical properties of the catalyst surface, for example, by adding adatoms of another element we call here "modifier".…”

Excitability in the H2+O2 reaction on a Rh(110) surface induced by high coverages of coadsorbed potassium

“…The Rh(110) surface was chosen as substrate because of its enormous structural variability as evidenced by a large number of different reconstructions induced by adsorbates. 12 In the case of O 2 + H 2 reaction, the strong attraction between K and O caused their condensation into coadsorption islands resulting in the formation of Turing-like stationary concentration patterns. How periodic structures can develop in a system governed by attractive interactions has been explained with the concept of reactive phase separation.…”