Coupling between Adjacent Crystal Planes during CO + O_ad Reaction on a Defective Pd(100) Surface

Abstract

Spatially resolved photoemission electron microscopy (PEEM) was employed to investigate the adsorption, diffusion, and reactivity of oxygen on a defective Pd(100) surface. The defective region on Pd(100) exposed several different planes with low indexes, for example, (110) and (111) planes. Upon oxygen adsorption, various types of oxygen species formed on each plane, which behaved with different reactivities toward CO. An obvious coupling between the Pd(110) plane and its adjacent planes was monitored by PEEM during CO + Oad reaction and resulted in the appearance of the reaction-diffusion waves on the Pd (110) plane. The occurrence of reaction coupling had a great influence on the catalytic kinetics of the crystal planes involved. However, during isothermal desorption of adsorbed oxygen on the planes, no coupling existed between adjacent planes, which implied that the reaction played a key role in the occurrence of coupling.

Reduction of Cu2O nanocrystals: reactant-dependent influence of capping ligands and coupling between adjacent crystal planes

“…Such a concept has been previously validated by surface science studies of model systems of metallic catalysts. [2][3][4][5][6][7] Our results for the first time confirm this concept in powder oxide catalysts under realistic reaction conditions. Since the crystal plane exposed on the oxide surface determines not only its surface structure but also its surface composition, the catalytic activity and surface reactivity of the oxide surface are sensitively dependent on the exposed crystal plane.…”

“…Similar coupling between adjacent crystal planes has also been reported in other systems of metal model catalysts. [3][4][5][6][7] These results point to an important concept that the reaction kinetics of a polycrystalline nanoparticle cannot be regarded as a simple superposition of the contributions from each individual crystal plane exposed on the polycrystalline nanoparticle surface. Recently, the great progress in the controlled synthesis of inorganic materials makes it possible to prepare nanocrystals with a uniform and well-defined shape that can serve as model catalysts for the fundamental study of heterogeneous catalysis.…”

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

“…Reaction coupling between adjacent surfaces have been directly observed by PEEM on Pt polycrystalline and Pd polycrystalline during CO oxidation and hydrogen oxidation, in which surface species were imaged to diffuse between adjacent crystal planes with different activities. [16][17][18] In our case, reaction coupling between Pt(110) surface and AgPt interface occurs through the diffusion of CO ads between Pt sites with different activities. However, the observed reaction coupling between adjacent AgPt interface and Ag surface, in which CO ads diffuses from Pt sites to Ag sites, has not been reported before.…”

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.…”