Search

• 2D ZrS 2 /GaS van der Waals heterostructure (vdWH) were studied. • The electrical field changed the band alignment from type-II to type-I at -0.2 V/Å. • The biaxial strain changed the band alignment from type-II to type-I at -1% strain. • The compressive strain increase the optical adsorption coefficients in visible region. Via first-principle methods, the electronic structures and optical properties of 2D ZrS 2 /GaS van der Waals heterostructure (vdWH) are studied. It is found that the band alignment changes from type-II to type-I under negative electrical field, and compressive strains. The transition points are -0.2 V/Å and -1%, respectively. The band gap changes efficiently under positive electrical field and compressive strains. The tensile strains increase the optical adsorption coefficients in ultraviolet regions, while the compressive strains increase the optical adsorption coefficients in visible region significantly. [ABSTRACT FROM AUTHOR]

The structural stability of the Ni 4 and Ni 4−x Re x clusters on the yttria-stabilised zirconia (YSZ) surfaces under sulfur adsorption is systematically studied using a first-principles method based on density functional theory. It is found that the Ni 4−x Re x alloy cluster is more difficult to deform under sulfur adsorption than the pure Ni 4 cluster on the YSZ(1 1 1) surfaces. The results are helpful for explaining why Ni alloyed with Re is more tolerant for sulfur poisoning and provide guidance for designing Ni-based catalyst with high sulfur tolerance. [ABSTRACT FROM AUTHOR]

Abstract: The first-principles method based on density functional theory (DFT) is used to investigate the reaction mechanism for the adsorption of H2S on the oxygen-enriched yttria-stabilized zirconia (YSZ+O) (111) surface. It is found that the H2S dissociation processes have low energy barriers (<0.5eV) and high exothermicities (2.5eV), and the dissociative S atoms may result in the poisoning of the YSZ+O surface by forming the SO and the hyposulfite (SO2 2−) species with very strong bonds to the surface. In addition, using the ab initio atomistic thermodynamics method, the surface regeneration or de-sulfurization process of a sulfur-poisoned (i.e. sulfur-covered) YSZ+O(111) surface is studied. According to the phase diagram, the adsorbed atomic sulfur can be oxidized to SO2 and removed from the YSZ+O surface by introducing oxidizing reagents, e.g. O2 and H2O. [Copyright &y& Elsevier]

The dissociation barriers of O and the adsorption energies of atomic O on the icosahedron M@Pd12, double icosahedron M2@Pd17 core-shell nanoclusters, and the M@Pd (M = Mn, Fe, Co, Ni, Cu, Pd) nanowires (NWs) are studied. It is found that the M@Pd NWs can probably serve as good catalysts for oxygen reduction reaction with both small O dissociation energy (0.10-0.23 eV) and O adsorption energy (1.19-1.28 eV). The reasons for the advantage of the M@Pd NWs are discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption, diffusion and dissociation properties of O2 on the icosahedron (Ih) Ni@Pt12 core–shell nanoparticle were investigated using the ab initio density functional theory calculations. It is found that, compared with the Pt(111) surface, the Ih Ni@Pt12 core–shell nanoparticle can enhance the adsorption, diffusion and dissociation of O2, as well as the adsorption and diffusion of the atomic O (the dissociation product of O2), and therefore serve as a good catalyst for oxygen reduction reaction. Our study gives a reasonable theoretical explanation to the high catalytic activity of the Ni@Pt core–shell nanoparticles for the oxygen reduction reaction. [Copyright &y& Elsevier]

By means of first-principle methods, the electronic structures and optical properties of 2D SnS 2 /GaS van der Waals heterostructure (vdWH) were studied. It was found that the band gap values could be modulated by vertical electrical. Besides, the biaxial strain not only tuned the band gap, but also changed the band alignment from type-II to type-I, realizing multi-functional device applications. The positive E-field increase the optical adsorption coefficients in visible region, while the negative E-field decrease the optical adsorption coefficients in visible region and increase the optical adsorption coefficients in ultra-violet region. The tensile strains increase the optical adsorption coefficients in infrared, visible and ultraviolet regions, while the compressive strain decrease the optical adsorption coefficients in visible and ultraviolet region. The results show that the tensile strain and E-field both can modulate the band gap to enhance performance in the visible optical application for SnS 2 /GaS vdWH materials, but the tensile strain is more efficient. Image 1 • 2D SnS 2 /GaS van der Waals heterostructure (vdWH) were studied. • The band gap values keep linear decease from −0.4 to 0.4 eV Å−1 • The biaxial strain changed the band alignment from type-II to type-I at −3% strain. • The positive E-field increase the optical adsorption coefficients in visible region. • The tensile strain increase the optical adsorption coefficients in visible region. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption and dissociation of H2S on the yttria-stabilized zirconia (YSZ) (111) surface are studied using the first-principles methods. It is found that H2S and SH species are bound weakly on the YSZ(111) surface. Sulfur atom is essentially immobile both into the YSZ bulk and along the surface. Instead, it is stably anchored on the O atop of the YSZ surface with the formation of the SO2− fragment. The nudged elastic band (NEB) calculations show that the formation of SH from H2S (H2S → SH + H) is very easy, while the presence of a co-adsorbed H would inhibit the further dissociation of SH. In contrast, the hydrogenation of the adsorbed sulfur is rather easy. It is concluded that H could inhibit the formation of sulfur, thus the sulfur poisoning of the YSZ surface would be prevented by hydrogen. [Copyright &y& Elsevier]

Abstract: The adsorption, diffusion and dissociation properties of O2, as well as adsorption and diffusion properties of O on the Ih Cu@Pt12 core–shell nanoparticle are studied using the ab initio density functional theory (DFT) calculations. It is found that the O2 can easily dissociate and the O can easily diffuse on the Ih Cu@Pt12 with much lower barriers as compared those on the Pt(111) surface, which demonstrates the much higher oxygen reduction activity of the Ih Cu@Pt12 core–shell nanoparticles. [Copyright &y& Elsevier]

The adsorption properties of CO on the nondefective and defective (with an oxygen vacancy) B-layer Fe 3 O 4 (0 0 1) surfaces (an octahedral environment of iron ions) at different coverages are studied using the spin-polarized density functional theory with the inclusion of on-site Coulomb interaction by introducing Hubbard U parameter (DFT + U) method. It is found that the CO adsorption energy in general increases with the CO coverage. Both types of B-layer Fe 3 O 4 (0 0 1) surfaces have the excellent ability for CO oxidation. Comparatively, the defective B-layer Fe 3 O 4 (0 0 1) surface has a much stronger CO adsorption ability and a lower CO oxidation ability than the nondefective B-layer Fe 3 O 4 (0 0 1) surface. The density of state reveals the bonding mechanism of CO on the two surfaces. The effects of the ambient conditions on the CO adsorption processes are analyzed. [ABSTRACT FROM AUTHOR]