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Hydrogenation is an effective approach to improve the performance of photocatalysts within defect engineering methods. The mechanism of hydrogenation and synergetic effects between hydrogen atoms and local electronic structures, however, remain unclear due to the limits of available photocatalytic systems and technical barriers to observation and measurement. Here, we utilize oxygen vacancies as residential sites to host hydrogen atoms in a layered bismuth oxychloride material containing defects. It is confirmed theoretically and experimentally that the hydrogen atoms interact with the vacancies and surrounding atoms, which promotes the separati30on and transfer processes of photo-generated carriers via the resulting band structure. The efficiency of catalytic activity and selectivity of defective bismuth oxychloride regarding nitric oxide oxidation has been improved. This work clearly reveals the role of hydrogen atoms in defective crystalline materials and provides a promising way to design catalytic materials with controllable defect engineering. Hydrogenated BiOCl shows high performance as a semiconductor photocatalyst, but the mechanism and synergetic effects of hydrogenation are hard to study. Here interactions of oxygen vacancies and hydrogen atoms in BiOCl nanosheets show a modulation of energy dispersion, which leads to both improvements in charge separation and photocatalytic activity. [ABSTRACT FROM AUTHOR]

The detailed catalytic oxidation mechanisms of CO over Cr-embedded graphene have been investigated by means of M06-2X density functional. Both models with chromium atom embedded in single and double vacancy (Cr-SV and Cr-DV) in a graphene sheet were considered. It is found that the CO oxidation on Cr-SV-graphene prefers to Langmuir-Hinshelwood (LH) mechanism, while the Cr-DV-graphene shows good catalytic activity toward the CO oxidation via the Eley-Rideal (ER) mechanism. The present results imply that the low-cost Cr-embedded graphene is a prospective catalyst for CO oxidation at room temperature. [ABSTRACT FROM AUTHOR]

In the present work, pure CeO2, neodymium-doped CeO2, and neodymium and transition metal element (Cu, Zn, Cr)-codoped CeO2 nanoparticles were synthesized by an auto-combustion method and annealed at 700 ∘C. The X-ray diffraction (XRD) studies revealed that all the samples exhibited a single-phase cubic fluorite structure with the incorporation of respective dopant ions into the CeO2 lattice. The scanning electron microscopy (SEM) images displayed the prepared nanoparticles which had an irregular flaky structure with large agglomerations. The Fourier transform Raman (FT-Raman) spectroscopy analysis revealed the increased oxygen vacancy defects in CeO2 host after doping and codoping with neodymium and transition metal elements. Ultraviolet-diffuse reflectance spectroscopy (UV-DRS) studies revealed the decrease in bandgap values in doped and codoped samples compared to pure CeO2 sample. The Fourier transform infrared spectroscopy (FTIR) studies revealed the presence of functional groups in the prepared samples. Photoluminescence (PL) spectroscopy analysis reported the decreased luminescence intensities of Nd-doped and neodymium and transition metal-codoped CeO2 nanoparticles. The vibrating sample magnetometer (VSM) results depicted that all the samples exhibited room-temperature ferromagnetism. [ABSTRACT FROM AUTHOR]

The effects of Fe ion vacancy on structural and magnetic properties of NiFeO4 nanoparticles are investigated using X-ray diffraction, Fourier transform infrared, morphological, and magnetic measurements. The introduction of Fe ion vacancy leads to the increase of the lattice parameter and decrease of the particle size. Moreover, vibrating sample magnetometer measurement results revealed that the values of the magnetization decreased and that coercivity had no regular behavior with increasing Fe ion vacancy content. These behaviors could be explained by considering cation distribution in the spinel structure. The estimated cation distribution results show that the Fe ion vacancy mostly occurred at the B sites which is in good agreement with the theoretical calculations. [ABSTRACT FROM AUTHOR]

Thermal effects are important considerations at the initial stage in spark plasma sintering of non-conductive AlO powders. The generalized thermo-elastic theory is introduced to describe the influence of the heat transport and thermal focusing caused by thermal wave propagation within a constrained space and transient time. Simulations show that low sintering temperature can realize high local temperature because of the superposition effect of heat waves. Thus, vacancy concentration differences between the sink and the cross section of the particles increase relative to that observed during pressure-less and hot-pressure sintering. Results show that vacancy concentration differences are significantly improved during spark plasma sintering, thereby decreasing the time required for sintering. [ABSTRACT FROM AUTHOR]

Phosphorene is receiving great research interests because of its peculiar physical properties. Nonetheless, no systematic studies on the transport properties modified due to defects have been performed. Here, we present the electronic band structure, defect formation energy and bias dependent transport property of various defective systems. We found that the defect formation energy is much less than that in graphene. The defect configuration strongly affects the electronic structure. The band gap vanishes in single vacancy layers, but the band gap reappears in divacancy layers. Interestingly, a single vacancy defect behaves like a p-type impurity for transport property. Unlike the common belief, we observe that the vacancy defect can contribute to greatly increasing the current. Along the zigzag direction, the current in the most stable single vacancy structure was significantly increased as compared with that found in the pristine layer. In addition, the current along the armchair direction was always greater than along the zigzag direction and we observed a strong anisotropic current ratio of armchair to zigzag direction. [ABSTRACT FROM AUTHOR]

We describe a one-step, deterministic and scalable scheme for creating macroscopic arbitrary entangled coherent states (ECSs) of separate nitrogen-vacancy center ensembles (NVEs) that couple to a superconducting flux qubit. We discuss how to generate the entangled states between the flux qubit and two NVEs by the resonant driving. Then the ECSs of the NVEs can be obtained by projecting the flux qubit, and the entanglement detection can be realized by transferring the quantum state from the NVEs to the flux qubit. Our numerical simulation shows that even under current experimental parameters the concurrence of the ECSs can approach unity. We emphasize that this method is straightforwardly extendable to the case of many NVEs. [ABSTRACT FROM AUTHOR]