Electronic Structure Of Surface Layer Research Articles

Singlet oxygen generation boosted by Ag–Pt nanoalloy combined with disordered surface layer over TiO2 nanosheet for improving the photocatalytic activity

The activation of molecular oxygen with photoinduced charge carriers are highly vital in photocatalysis. Here, the synergetic effects of disordered surface layer and Ag–Pt nanoalloy over TiO2 nanosheet on the improved photocatalytic activity was proposed. The nanocomposites exhibited enhanced photocatalytic performance in selective oxidation of benzylamine to imine under UV–visible irradiation. More importantly, the synergetic effect of nanoalloy and surface oxygen vacancy boosted the generation of singlet oxygen in the selective oxidation of benzylamine. The regulation of thickness of disordered surface layer and composition of Ag–Pt nanoalloy over nanosheet TiO2 promoted the separation efficiency and mobility of charge carriers, resulted from the changed electronic structure of surface layer and nanoalloy. These findings provide an avenue for the design of nanocomposite photocatalysts combined defect engineering and nanoalloy modification to improve the photocatalytic activity.

Peculiar symmetry-protected electronic dispersions in two-dimensional materials

Symmetry indicates that low energy spectra of materials could be richer than well-known Dirac, semi-Dirac, or quadratic, hosting some unusual quasiparticles. Performing the systematic study of exact forms of low energy effective Hamiltonians and dispersions in high-symmetry points with fourfold degeneracy of bands, we found new, previously unreported dispersion, which we named poppy flower (PF) after its shape. This massless fermion exists in non-magnetic two-dimensional (2D) crystals with spin–orbit coupling (SOC), which are invariant under one of the proposed ten noncentrosymmetric layer groups. We suggest real three-dimensional (3D) layered materials suitable for exfoliation, having layers that belong to these symmetry groups as candidates for realization of PF fermions. In 2D systems without spin–orbit interaction, fortune teller (FT)-like fermions were theoretically predicted, and afterward experimentally verified in the electronic structure of surface layer of silicon. Herein, we show that such fermions can also be hosted in 2D crystals with SOC, invariant under additional two noncentrosymmetric layer groups. This prediction is confirmed by density functional based calculation: layered BiIO4, which has been synthesized already as a 3D crystal, exfoliates to stable monolayer with symmetry pb21a, and FT fermion is observed in the band structure. Analytically calculated density of states (DOS) of the PF shows semimetallic characteristic, in contrast to metallic nature of FT having non-zero DOS at the bands contact energy. We indicate possibilities for symmetry breaking patterns which correspond to the robustness of the proposed dispersions as well as to the transition from Dirac centrosymmetric semimetal to PF.

Milling-induced phenomena in SrTiO3

The effect of milling was studied for the SrTiO3 samples. We show that by solid state reaction and subsequent milling it is possible to produce SrTiO3 powders with high specific surface area exceeding 10m2/g. However, grinding process induced changes in chemical composition and electronic structure of surface layers of SrTiO3 crystal grains. The changes are discussed in the context of kinetic demixing phenomena and partial amorphization of the surface region.

Quantum chemical study of catalysts based on oxides of transition metals

Abstract Catalysts based on oxides of transition metals were studied by X(I-DV calculations. The chemical composition and electronic structure of surface layers for platinum(1V) oxide catalysts modified under percompound electrosynthesis were determined by X-ray photoelectron spectroscopic, quantum chemical, and electrochemical data. The main regularities in electronic structure change under the transition from solid pure oxide Pt02 to its, in part, N-substituted Pt02,Nx were analyzed. Then, we looked for perspective catalysts, calculating the electronic structure for analogous compounds of Ir(III), Ir(IV), Rh(III), and Pd(I1). We found that the changes in electronic structure of rhodium oxide under 0 -N-substitution allowed us to predict the excellent properties of its compound as a catalyst for percompound electrosynthesis reactions. 0 1994 John Wiley & Sons, Inc. 1. Introduction Anodic processes on platinum electrodes under potential 1 B take place more easily on oxidized surfaces

Surface segregation and catalytic properties of PdRu alloys

Abstract A model for the electronic structure of surface layers of transition metal alloys is suggested. The model has been applied for the calculation of the electron density of states and surface segregations in Pd-Ru alloys. An analysis of experimental results concerning catalytic propErtles of the same alloys has been carried out and a mechanism for catalytic hydrogenation of acetylenic alcohols has been proposed.

Surface segregation and catalytic properties of Pd-Ru alloys

A model for the electronic structure of surface layers of transition metal alloys is suggested. The model has been applied for the calculation of the electron density of states and surface segregations in Pd-Ru alloys. An analysis of experimental results concerning catalytic propErtles of the same alloys has been carried out and a mechanism for catalytic hydrogenation of acetylenic alcohols has been proposed.