A first-principles study of Pt thin films on SrTiO3(100): Support effects on CO adsorption

Review of Systematic Tendencies in (001), (011) and (111) Surfaces Using B3PW as Well as B3LYP Computations of BaTiO3, CaTiO3, PbTiO3, SrTiO3, BaZrO3, CaZrO3, PbZrO3 and SrZrO3 Perovskites

We performed B3PW and B3LYP computations for BaTiO3 (BTO), CaTiO3 (CTO), PbTiO3 (PTO), SrTiO3 (STO), BaZrO3 (BZO), CaZrO3 (CZO), PbZrO3 (PZO) and SrZrO3 (SZO) perovskite neutral (001) along with polar (011) as well as (111) surfaces. For the neutral AO- as well as BO2-terminated (001) surfaces, in most cases, all upper-layer atoms relax inwards, although the second-layer atoms shift outwards. On the (001) BO2-terminated surface, the second-layer metal atoms, as a rule, exhibit larger atomic relaxations than the second-layer O atoms. For most ABO3 perovskites, the (001) surface rumpling s is bigger for the AO- than BO2-terminated surfaces. In contrast, the surface energies, for both (001) terminations, are practically identical. Conversely, different (011) surface terminations exhibit quite different surface energies for the O-terminated, A-terminated and BO-terminated surfaces. Our computed ABO3 perovskite (111) surface energies are always significantly larger than the neutral (001) as well as polar (011) surface energies. Our computed ABO3 perovskite bulk B-O chemical bond covalency increases near their neutral (001) and especially polar (011) surfaces.

First-Principles Study of the Effect of Titanium Doping on Carbon Monoxide Poisoning Properties of Zirconium-Cobalt Alloys

It is very important to study impurity gas poisoning in ZrCo alloy because it is associated directly with the performance of ZrCo alloy as a hydrogen storage material. In this work, the effects of atomic replacement on the mechanism and properties of CO impurity gas poisoning in doped (Ti) ZrCo hydrogen storage alloys were investigated using the first principles method, based on the pseudopotential plane wave method. The adsorption energy, lattice constant, density of states, and charge density difference of the compounds before and after doping were calculated. Then, surface adsorption models of the ZrCo and Zr0.8Ti0.2Co alloys were established with the assistance of a conventional model. The resulting adsorption energy values of the clean surface and the surface adsorption energy values in the presence of CO impurity gases manifested that the Ti element-doped Zr0.8Ti0.2Co alloy was more susceptible to CO gas poisoning compared to ZrCo, which was consistent with the existing experimental results. In addition, by analyzing the conventional model, the electrons from the doped atoms overlapped with the surrounding electrons of C atoms, the phenomenon of orbital hybridization occurred, and the interactions increased. Consequently, Ti doping was not conducive to ZrCo to improve the ability to resist CO poisoning. The research results of this paper have laid a good foundation for the study of the effect of Ti doping on the antitoxicity performance.

Ba-addition induced enhanced surface reducibility of SrTiO3: implications on catalytic aspects

Surface reducibility engineering is one of the vital tools to enhance the catalytic activity of materials. A heavy redox treatment can be utilized to affect the structure and surface of catalytic materials. Here, we choose SrTiO3 (STO) with a cubic perovskite structure as a system to induce oxygen vacancies by using nascent hydrogen from NaBH4 leading to a heavily reduced version of SrTiO3 (RSTO). To further understand the surface reduction and its dependence on foreign-ion (Ba) incorporation into SrTiO3, Sr0.5Ba0.5TiO3 (SBTO) and BaTiO3 (BTO) are synthesized using a facile hydrothermal method. The reduced version of the pristine and mixed oxide shows distinct optical absorptions, indicating oxygen vacancy-mediated reducibility engineering. Detailed CO oxidation experiments suggest the order of activity over the as-prepared and reduced supports as STO > SBTO > BTO and RSBTO > RSTO > RBTO, respectively. The interesting observation of reversal of CO oxidation activity over STO and SBTO after reduction negates the assumption of a similar intensity of reduction on the surfaces of these oxide supports. The fundamental aspect of surface reducibility is addressed using temperature programmed reduction/oxidation (TPR/TPO) and XPS.

Tuning oxygen electrocatalysis via strain on LaNiO3(001)

Theoretical insights into the influence of strain on the mechanisms of the oxygen evolution and oxygen reduction reactions on LaNiO₃(001).

Oxygen vacancies at the Au/SrTiO3(001) interface: stabilities, electronic properties and effect on photocatalysis

Oxygen vacancies have proven to induce various and important effects on the properties of materials. In the present work, the thermodynamic stabilities and electronic properties of oxygen vacancies (Ov) on the SrTiO₃ (STO)(001) surface and at the Au/STO(001) interface are systematically investigated by means of first-principles calculations. Both the SrO and TiO₂ terminated (001) surfaces of STO are examined. It is found that the Ov located in the near-surface region of the two surfaces can be divided into three categories according to their properties: Ov in the surface atomic layer, Ov in the subsurface TiO₂ atomic layers, and Ov in the subsurface SrO atomic layers. Counter-intuitively, for the SrO terminated surface the most stable site of Ov is in the first subsurface atomic layer. The Au metal in the Au/STO heterostructure significantly promotes the formation of Ov at and near the interface and thermodynamically promotes migration of Ov to the interfacial atomic layer. Furthermore, the interface Schottky barrier height is highly sensitive to both the concentration and position of Ov at the interface. These results are beneficial for the atomic-level understanding of the performance of STO-based photocatalysts and the rational design of more efficient ones.