CO Adsorption on the O-saturated Ag/Pt(110) Composite Surface:  Direct Observation of the Diffusion of Adsorbed CO from Strongly Bound Pt Sites to Weakly Bound Ag Sites

Abstract

In our work, photoemission electron microscopy (PEEM) was employed to real-time and in situ study CO adsorption on the O-saturated Ag/Pt(110) composite surface. Coupling occurred between adjacent surfaces with different activities for CO + O ad reaction, in which adsorbed CO was directly observed to migrate from strongly bound Pt sites to weakly bound Ag sites in the form of reaction-diffusion wave. Our results imply that surface species may migrate not only from weakly bound sites to strongly bound sites (enthalpy favorable process) but also from strongly bound sites to weakly bound sites (enthalpy unfavorable process) during heterogeneous catalysis reactions.

On the Propagation Rate of the Chemical Waves Observed during the Course of CO Oxidation on a Ag/Pt(110) Composite Surface

“…5 Other reported systems include CO oxidation, hydrogen oxidation, and NO reduction on the polycrystal of Pt and Pd, [6][7][8] the Cu-modified Pt(111) surface, 9 the microdesigned Pt(110) single-crystal surface with active Pd, Rh boundaries, [10][11][12][13] and the Ag/Pt(110) composite surface. [14][15] The propagation rates of chemical waves on solid surfaces seem to be specific with the individual reaction system. During the course of the oscillatory CO oxidation on a Pt(100) surface, the observed chemical wave propagates with a rate of 0.5-3 mm/min.…”

Surface Chemistry and Catalytic Properties of Well-Defined Cu2O Nanocrystals

“…As shown in Figure 9(A) and (B), reduced either by H 2 or CO, the reduction temperature of o-Cu 2 O-PVP is lower than that of c-Cu 2 O by more than 120 °C. This has been directly observed employing model catalyst approaches [7][8][9] and points to an important concept that the reaction kinetics of a polycrystalline particle cannot be regarded as a simple superposition of the contributions from each individual crystal plane exposed on its surface. Two factors determine the reactivity of a solid particle in the gas-solid chemical reactions: the surface reactivity of the solid particle and the adsorption/activation of gas molecules on the solid particle surface.…”

“…For multicomponent catalysts, the interfacial structure between adjacent components is also vital for their catalytic property. Thus the structure-catalytic property relation learned from single crystalsbased model catalysts sometimes cannot be simply extended to practical heterogeneous catalytic reactions and meanwhile several issues in practical heterogeneous catalytic reactions cannot be adequately approached using single crystals-based model catalysts [7][8][9][10][11]. Although we are able to comprehensively characterize the catalyst surface structure, surface adsorbates/ intermediates and catalytic property, the inhomogeneity of catalyst particles in their sizes and morphologies makes the unambiguous correlation between the catalyst surface structure and the catalytic property very difficult.…”

Degradation of Trichloroethylene by Iron-Based Bimetallic Nanoparticles

“…The definition of the rate constants can be found in nomenclature. Transmigration of the inactive-sorbed TCE in (9) between adjacent reactive sites can occur on the metal surface, and such phenomena have been observed and reported in the literature [14]: $${\mathrm{normalC}}_2{\text{HCl}}_{3^{-}}{\mathrm{normalS}}_{\mathrm{normali}}\underset{k_{-\mathrm{S}\mathrm{i}}}{\overset{k_{{\mathrm{normalS}}_{\mathrm{normali}}}}{\rightleftharpoons }}{\mathrm{normalC}}_2{\text{HCl}}_3-{\mathrm{normalS}}_{\mathrm{normali}}$$…”