Positive Charge Holes Revealed by Energy Band Theory in Multiphase Tix O2x-1 and Exploration of its Microscopic Electromagnetic Loss Mechanism

Although numerous experimental investigations have been carried out on the problem of defect engineering in semiconductor absorbers, the relationship among charge carrier, defects, heterointerfaces, and electromagnetic (EM) wave absorption has not been established systematically. Herein, the new thermodynamic and kinetic control strategy is proposed to establish multiphase Tix O2 x -1 (1 ≤ x ≤ 6) through a hydrogenation calcination. The TiOC-900 composite shows the efficient EM wave absorption capability with a minimum reflection loss (RLmin ) of -69.6 dB at a thickness of 2.04 mm corresponding to an effective absorption bandwidth (EAB) of 4.0 GHz due to the holes induced conductance loss and heterointerfaces induced interfacial polarization. Benefiting from the controllable preparation of multiphase Tix O2 x -1 , a new pathway is proposed for designing high-efficiency EM wave absorbing semiconducting oxides. The validity of the method for adopting energy band theory to explore the underlying relations among charge carriers, defects, heterointerfaces, and EM properties in multiphase Tix O2 x -1 is demonstrated for the first time, which is of great importance in optimizing the EM wave absorption performance by electronic structure tailoring.

Robust Porous WC-Based Self-Supported Ceramic Electrodes for High Current Density Hydrogen Evolution Reaction

Developing an economical, durable, and efficient electrode that performs well at high current densities and is capable of satisfying large-scale electrochemical hydrogen production is highly demanded. A self-supported electrocatalytic "Pt-like" WC porous electrode with open finger-like holes is produced through industrial processes, and a tightly bonded nitrogen-doped WC/W (WC-N/W) heterostructure is formed in situ on the WC grains. The obtained WC-N/W electrode manifests excellent durability and stability under multi-step current density in the range of 30-1000 mA cm-2 for more than 220 h in both acidic and alkaline media. Although WC is three orders of magnitude cheaper than Pt, the produced electrode demonstrates comparable hydrogen evolution reaction performance to the Pt electrode at high current density. Density functional theory calculations attribute its superior performance to the electrode structure and the modulated electronic structure at the WC-N/W interface.

Establishing a new hot electrons transfer channel by ion doping in a plasmonic metal/semiconductor photocatalyst

A straightforward strategy is developed to improve the injection efficiency of hot electrons in a Ag/TiO2 plasmonic photocatalyst by introducing Fe as a dopant. The Fe dopant energy level formed within the bandgap of TiO2 provides an extra electron transfer channel for transferring the hot electrons induced by plasmonic Ag nanoparticles.

Co-site substitution by Mn supported on biomass-derived active carbon for enhancing magnesia desulfurization

Oxidation of magnesium sulfite (MgSO₃) is a crucial step for reclaiming the product in wet magnesia desulfurization processes. Here, for enhancing this reaction, a bimetallic catalyst was developed by loading CoO_x and MnO_x species on a biomass-derived active carbon (AC) support to minimize the costs and potential environmental risks during catalyst application. The substitution effect of Mn to Co sites was investigated, and a comparison of the catalyst with plain cobalt suggested that the ratio of Co/Mn must be greater than 3. A series of catalyst characterizations was performed to reveal the synergistic effect of Co and Mn in the bimetallic catalyst. The introduction of Mn species not only improved the dispersion of CoO_x-MnO_x mixed oxide but also generated abundant Co³⁺ species and surface-adsorbed oxygen, both of which acted as the main active sites for sulfite oxidation. Notably, in the bimetallic catalyst, the presence of Mn⁴⁺ species assisted regeneration of Co²⁺ to Co³⁺ species, further accelerating sulfite oxidation. Besides, the partial substitution of Co sites by Mn also suppressed the losing of Co species during reaction, favoring to decrease the environmental risk, as well as to save the cost of catalyst.

The formation and detection techniques of oxygen vacancies in titanium oxide-based nanostructures

TiO2 and other titanium oxide-based nanomaterials have drawn immense attention from researchers in different scientific domains due to their fascinating multifunctional properties, relative abundance, environmental friendliness, and bio-compatibility. However, the physical and chemical properties of titanium oxide-based nanomaterials are found to be explicitly dependent on the presence of various crystal defects. Oxygen vacancies are the most common among them and have always been the subject of both theoretical and experimental research as they play a crucial role in tuning the inherent properties of titanium oxides. This review highlights different strategies for effectively introducing oxygen vacancies in titanium oxide-based nanomaterials, as well as a discussion on the positions of oxygen vacancies inside the TiO2 band gap based on theoretical calculations. Additionally, a detailed review of different experimental techniques that are extensively used for identifying oxygen vacancies in TiO2 nanostructures is also presented.

Effect of Synthetic Method and Annealing Temperature on the Structure of Hollandite-Type Oxides

Hollandite is a class of metal oxide material with the general formula A₂B₈O₁₆. Several methods have been used in the synthesis of this type of metal oxide, and the synthetic methods reported have typically employed high annealing temperatures between 1200 and 1300 °C. Appropriate synthetic methods must be employed to successfully synthesize these hollandite-type oxides at lower annealing temperatures. Hollandite compounds have been synthesized using ceramic (high annealing temperature only) and coprecipitation (high and low annealing temperatures) methods. Annealing temperatures ranging from 1200 to 700 °C have been employed in the thermal treatment process. Powder X-ray diffraction and X-ray absorption near-edge spectroscopy (XANES) were conducted on hollandite-type oxides (Ba _xAl_{2 x}Ti_{8-2 x}O_16-δ; x = 1.2; and Ba _xAl _xFe _xTi_{8-2 x}O_16-δ, Ba _xFe_{2 x}Ti_{8-2 x}O_16-δ; x = 1.16). Structural comparisons between materials annealed in the temperature range from 1200 to 800 °C were made, and an examination of the XANES spectra and powder X-ray diffraction patterns has provided confirmation of the absence of significant structural changes in these hollandite materials. This study has shown that hollandite-type materials can be formed using annealing temperatures as low as 700-800 °C when a coprecipitation method is used, with little change to the local and long-range structures being detected.

Investigation of CeTi2O6- and CaZrTi2O7-containing glass–ceramic composite materials

Glass–ceramic composite materials are being investigated for numerous applications (i.e., textile, energy storage, nuclear waste immobilization applications, etc.) due to the chemical durability and flexibility of these materials. Borosilicate and Fe–Al–borosilicate glass–ceramic composites containing brannerite (CeTi2O6) or zirconolite (CaZrTi2O7) crystallites were synthesized at different annealing temperatures. The objective of this study was to understand the interaction of brannerite or zirconolite-type crystallites within the glass matrix and to investigate how the local structure of these composite materials changed with changing synthesis conditions. Powder X-ray diffraction (XRD) and Backscattered electron (BSE) microprobe images have been used to study how the ceramic crystallites dispersed in the glass matrix. X-ray absorption near edge spectroscopy (XANES) spectra were also collected from all glass–ceramic composite materials. Examination of Ti K-, Ce L3-, Zr K-, Si L2,3-, Fe K-, and Al L2,3-edge XANES spectra from the glass–ceramic composites have shown that the annealing temperature, glass composition, and the loading of the ceramic crystallites in the glass matrix can affect the local environment of the glass–ceramic composite materials. A comparison of the glass–ceramic composites containing brannerite or zirconolite crystallites has shown that similar changes in the long range and local structure of these composite materials occur when the synthesis conditions to form these materials or the composition are changed.

Plasma modification of the electronic and magnetic properties of vertically aligned bi-/tri-layered graphene nanoflakes

Saturation magnetization of vertically aligned bi/tri-layers is further enhanced by hydrogen, nitrogen plasma modification while organo-silane treatment reduces magnetization.

A study of the electronic structure and structural stability of Gd2Ti2O7 based glass-ceramic composites

Glass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements.

Robust SiO2-modified CoFe2O4 hollow nanofibers with flexible room temperature magnetic performance

Flexible room temperature magnetic parameters (M_s and H_c) of electrospun SiO₂-modified CoFe₂O₄ hollow nanofibers annealed at 1000 °C.

Fabrication of porous TiO2–SiO2 multifunctional anti-reflection coatings by sol–gel spin coating method

Fabrication of a self-cleaning anti-reflection coating that can degrade gaseous pollutants and applied contaminants to maintain long-term transmittance property.

Oxide-based inorganic/organic and nanoporous spherical particles: synthesis and functional properties

This paper reviews the recent progress in the preparation of oxide-based and heteroatom-doped particles. Surfactant-templated oxide particles, e.g. silica and titania, are possible candidates for various potential applications such as adsorbents, photocatalysts, and optoelectronic and biological materials. We highlight nanoporous oxides of one element, such as silicon or titanium, and those containing multiple elements, which exhibit properties that are not achieved with individual components. Although the multicomponent nanoporous oxides possess a number of attractive functions, the origin of their properties is hard to determine due to compositional/structural complexity. Particles with a well-defined size and shape are keys for a quantitative and detailed discussion on the unique complex properties of the particles. From this viewpoint, we review the synthesis techniques of the oxide particles, which are functionalized with organic molecules or doped with heteroatoms, the physicochemical properties of the particles and the possibilities for their photofunctional applications as complex systems.