Oxygen Vacancy Induced Charge Transfer in All Inorganic S‐Scheme Heterojunction for Efficient CO 2 Photoreduction to Solar Fuels

Tunable Bi-bridge S-scheme Bi2S3/BiOBr heterojunction with oxygen vacancy and SPR effect for efficient photocatalytic reduction of Cr(VI) and industrial electroplating wastewater treatment

Oxygen-defected WO3-OVs@Bi2MoO6 S-scheme micro flowers heterojunctions with promoted photocatalytic degradation of tetracycline

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp ³ )–H Bond Activation

Bi2MoO6/MgIn2S4 S-scheme heterojunction with rich oxygen vacancies for effective organic pollutants degradation: Degradation pathways, biological toxicity assessment, and mechanism research

Improved piezo-photocatalytic activity by controlling the oxygen vacancy content of NaNbO3 powders

There is a great concern about black TiO2 prepared by H2 treatment because of its ability to enhance light harvesting of TiO2. Black TiO2 shows different photocatalytic activities compared with white TiO2. However, the mechanism of photocatalytic reaction has not been clearly understood. Here, femtosecond time-resolved diffuse reflectance (fs-TRDR) spectroscopy and single-particle photoluminescence measurements were applied to gain better understanding about the relation between oxygen vacancy, charge transfer, lifetime of photogenerated charge, and photocatalytic activity. We prepared reduced TiO2 mesocrystals (R-TMC) through simple solid-state chemical reduction at moderate temperature 350 °C. R-TMC has nearly two times higher photocatalytic activity for H2 production under solar light irradiation. The presence of oxygen vacancies and Ti3+ was studied by electro paramagnetic resonance and X-ray photoelectron spectroscopy. This work confirms the findings of previous studies that enhancement of light abso...

Oxygen vacancy-suppression strengthened the internal electric field in ZnIn2S4/BiVO4 S-scheme heterojunction to boost photocatalytic removal of aqueous pollutants

Polypyrrole-decorated ZnO/g-C3N4 S-scheme photocatalyst for rhodamine B dye degradation: Mechanism and antibacterial activity

Highly sensitive electrochemical detection of Hg(II) promoted by oxygen vacancies of plasma-treated ZnO: XPS and DFT calculation analysis

Electronic structure of Pt/HfO 2 interface with oxygen vacancy

Proton exchange membrane fuel cells (PEMFCs) are expected one of the effective electrochemical energy-devices due to their high energy conversion efficiency and no environmental pollution. However, the large amount of Pt catalysts are used on the cathode electrode to promote the oxygen reduction reaction (ORR). In order to reduce the fuel cell cost, thus, the non-Pt alternative catalysts are required. The group 4 and 5 transition-metal oxides have been investigated as the non-Pt alternative catalysts. These oxide catalysts, which was made by the partial-oxidation of carbonitride, have high ORR activity [1]. Now, it is believed that the ORR arises at the oxygen vacancy site of oxide surface which acts as the active site. Moreover, the deposited carbon, which was residual carbon species of the organic metal precursor, would become the role of the micro electron-conduction path. However, the deposited carbon and the oxygen vacancies are not well understood whether how to be actually working on the active factors. In order to understand for an ORR-activity fundamental-factor, this study investigated that the group 4 and 5 transition-metal oxides (TiO2, ZrO2, Nb2O5) are how the relationship between ORR activity and the crystalline structure and size. Those samples were prepared by sol-gel methods. An organometallic compound (Ti(OC4H9)4, Zr(OC4H9)4, Nb(OC2H5)5), diethylene glycol and 1-penten-3-ol solution were mixed in 1-butanol. Gelatinization of the sol solution was conducted by addition of ultra-pure water. The obtained gel was calcination at 400 - 700ºC for 12 hours. The crystal structure was characterized by X-ray diffraction (XRD), and the chemical surface condition was analyzed by X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry measurement was conducted by the static three-electrode cell in 0.1 M HClO4. The ORR activity was evaluated by calculated the ORR currents (i ORR). The i ORR was calculated by subtracting the Ar saturated currents (i Ar) from the O2 saturated currents (i O2). The onset potential for the ORR (E ORR) was defined as the electrode potential at the starting of the i ORR. The diffraction peaks of the obtained samples at 700ºC were attributed to that of TiO2, ZrO2 and Nb2O5, respectively. The crystal structure of ZrO2 depended on the calcination temperature. In case of 700ºC, the crystal structure was only the orthorhombic. In case of calcination at 400 and 600ºC, not only the orthorhombic but also the cubic was detected. The peak intensity of the cubic structure became stronger by decreasing the calcination temperature. E ORR of ZrO2 at all calcination temperature was almost same and low. Thus, the crystal structure would not affect ORR activity. On the other hand, the crystallite size of all samples also depended on the calcination temperature. In the samples of Nb2O5, the crystallite size of 700ºC was estimated ~ 63 nm at 22.5º, whereas that of 400 and 300ºC were about several nanometers and no crystallinity, respectively. E ORR of Nb2O5 was the same potential in spite of different crystallite sizes. Therefore, the crystallite size also would not be relevant to ORR activity. The crystal structure and the crystallite size may be no relation to the ORR activity in group 4 and 5 oxides. Because E ORR of ZrO2 and Nb2O5 at different calcination temperature were almost the same potential and low. Therefore, it is thought that some active sites and electronic conduction paths like such the oxygen vacancies and the residual carbons are the most impacts for ORR. However, in the XPS measurement, the residual carbon has detected all samples. The residual carbon would be also no effect ORR activity since all samples showed the low E ORR. Thus, it is not as simple as that only the presence of oxygen vacancy and residual carbon lead to high ORR activity. In rare cases, some prepared oxide indicated the high ORR activity although its reproducibility was low. There is a possibility that other factors, which have not known yet, promotes ORR. For the future work, the ORR activity will be comparing with/without oxygen vacancies. reference [1] A. Ishihara, M. Tamura, Y. Ohgi, M. Matsumoto, K. Matsuzawa, S. Mitsushima, H, Imai, K. Ota, J. Phys. Chem. C, 117, 18837 (2013).

Two different murdochite-type mixed oxides, (Mg6−xLix)MnO8 (x = 0, 0.1, 0.2 and 0.3) and (Mg6−xAlx)MnO8 (x = 0, 0.2, 0.4, 0.6) were examined for the catalytic decomposition of N2O in order to make clear the effects of mixed valencies of pairing manganese ions and oxygen vacancies. The valence of manganese ions and the amount of surface oxygen vacancies have been examined with X-ray photoelectron spectroscopy (XPS). (Mg6−xLix)MnO8 had mixed valence manganese ions and oxygen vacancies on the surface after the substitution. The substituted (Mg6−xAlx)MnO8 had a mixed valence state but oxygen vacancies decresed with x and excess oxygen over stoichiometry was observed at x = 0.4 and 0.6. The reaction rate of N2O decomposition increased after substitution with lithium but hardly increased after the substitution with aluminum in (Mg6−xAx)MnO8. We assumed that the presence of oxygen vacancies on the surface along with pairing altervalent manganese ions affected strongly to enhance the reactivity of N2O decomposition.

We report on the structure and adsorption properties of Pd(n) (n = 1-4) clusters supported on the rutile TiO(2) (110) surfaces with the possible presence of a surface oxygen vacancy or a subsurface Ti-interstitial atom. As predicted by the density functional theory, small Pd clusters prefer to bind to the stoichiometric titania surface or at sites near subsurface Ti-interstitial atoms. The adsorption of Pd clusters changes the electronic structure of the underlying surface. For the surface with an oxygen vacancy, the charge localization and ferromagnetic spin states are found to be largely attenuated owing to the adsorption of Pd clusters. The potential energy surfaces of the Pd monomer on different types of surfaces are also reported. The process of sintering is then simulated via the Metropolis Monte Carlo method. The presence of oxygen vacancy likely leads to the dissociation of Pd clusters. On the stoichiometric surface or surface with Ti-interstitial atom, the Pd monomers tend to sinter into larger clusters, whereas the Pd dimer, trimer, and tetramer appear to be relatively stable below 600 K. This result agrees with the standard sintering model of transition metal clusters and experimental observations.

Most oxide semiconductor photoanode materials for water splitting are synthesized in ambient environment. Oxygen vacancy exists in these samples making them intrinsically n-type at the as-synthesized state. Oxygen vacancy has been widely reported for enhancing the performance of a photoanode by improving the electron conductivity. Besides the effect on the bulk materials properties, oxygen vacancy also plays an important role in the interfacial charge transfer to electrolyte, on which much less attention has been paid in the past. Herein, we found that although air-annealed W-doped BiVO4 has a higher electron density, lower surface charge transfer resistance, and a slightly better light absorption than the O2-annealed sample, the latter displays a higher photocurrent density. Experimentally we found that the enhanced performance comes from a better charge separation efficiency, despite that the presence of oxygen vacancy does lead to a better charge transfer efficiency. Theoretical calculation finds that ...

A facile and high-effective oxygen defect engineering for improving electrochemical performance of lithium-rich manganese-based cathode materials