Percolative Channels for Superionic Conduction in an Amorphous Conductor

All-solid-state batteries greatly rely on high-performance solid electrolytes. However, the bottlenecks in solid electrolytes are their low ionic conductivity and stability. Here we report a new series of amorphous xAgI·(1–x)Ag3PS4 (x = 0∼0.8 with interval of 0.1) conductors, among which the sample with x = 0.8 exhibits the highest ionic conductivity (about 1.1 × 10–2 S cm-1) and ultrahigh chemical stability. We discovered the existence of mixed disordered Ag3PS4 and AgI clusters in the amorphous conductors using solid-state nuclear magnetic resonance spectroscopy. The high ionic conductivity was ascribed to the formation of the interconnecting AgI clusters, i.e., the percolative channels for superionic conduction. The composition dependence of the ionic conductivity for this series of amorphous conductors was clarified by a continuum percolation model. These findings provide fundamental guidance for designing and fabricating high-performance amorphous solid electrolytes for all-solid-state batteries

Percolative Channels for Superionic Conduction in an Amorphous Conductor

All-solid-state batteries greatly rely on high-performance solid electrolytes. However, the bottlenecks in solid electrolytes are their low ionic conductivity and stability. Here we report a new series of amorphous xAgI·(1–x)Ag3PS4 (x = 0∼0.8 with interval of 0.1) conductors, among which the sample with x = 0.8 exhibits the highest ionic conductivity (about 1.1 × 10–2 S cm-1) and ultrahigh chemical stability. We discovered the existence of mixed disordered Ag3PS4 and AgI clusters in the amorphous conductors using solid-state nuclear magnetic resonance spectroscopy. The high ionic conductivity was ascribed to the formation of the interconnecting AgI clusters, i.e., the percolative channels for superionic conduction. The composition dependence of the ionic conductivity for this series of amorphous conductors was clarified by a continuum percolation model. These findings provide fundamental guidance for designing and fabricating high-performance amorphous solid electrolytes for all-solid-state batteries

Role of Sodium Ion on TiO₂ Photocatalyst: Influencing Crystallographic Properties or Serving as the Recombination Center of Charge Carriers?

There have been continuing debates about the role of Na⁺ on TiO₂ photocatalyst in the past decades. Most researchers accepted that Na⁺ served as the recombination center of photogenerated electrons and holes. Nevertheless, other opinions also existed, such as Na⁺ increased the crystallite size of TiO₂, Na⁺ hampered the crystallization of anatase TiO₂, and Na⁺ promoted the formation of brookite TiO₂ or titanate sodium. In this research, we have systematically investigated the role of Na⁺ during the fabrication of TiO₂ film and powder through the sol–gel method and studied the influences of crystallinity and the content of Na⁺ on the photocatalytic activities of TiO₂ film and powder. It has been found that the existence of Na⁺ in TiO₂ film and powder should influence their crystallographic properties, in detail, inhibiting the crystallization and growth of anatase phase in TiO₂ film and powder, promoting the formation of brookite phase in TiO₂ film, and increasing the transformation temperature of anatase to rutile phase in TiO₂ powder. Even though the existence of Na⁺ forms the Ti–O–Na bond on the surface of TiO₂, however, the widely adopted hypothesis of Na⁺ serving as the recombination center of photogenerated electrons and holes is not correct

Preparation and Enhanced Photocatalytic Activity of TiO₂ Nanocrystals with Internal Pores

Anatase TiO₂ nanocrystals with internal pores are prepared by a novel facile microwave-assisted hydrolysis of a mixture of TiOCl₂ and HF aqueous solutions, followed by calcination at 400 °C. The TiO₂ nanocrystals with internal pores are characterized by XRD, TEM, SEM, BET, EDS, and XPS. The formation mechanism of the TiO₂ nanocrystals with internal pores is discussed by investigating the role of fluorine and the calcination. The photocatalytic measurement shows that the TiO₂ nanocrystals with internal pores exhibit much higher photocatalytic activity for the photodegradation of crystal violet, methyl orange, and 4-chlorophenol than the TiO₂ solid nanocrystals. The photocatalytic enhancement is due to the fluorination of TiO₂ nanocrystals as well as its unique hollow nanostructure, which results in the higher separation efficiency of photogenerated electrons and holes in the TiO₂ nanocrystals with internal pores than in its solid counterpart

Additional file 1: of Tuning the Optical Properties of CsPbBr3 Nanocrystals by Anion Exchange Reactions with CsX Aqueous Solution

Additional XRD patterns, TEM images, and PL spectra (DOCX 4026 kb

Thermal Insulation Monolith of Aluminum Tobermorite Nanosheets Prepared from Fly Ash

A thermal insulation monolith of aluminum tobermorite nanosheets was prepared by a facile method of one-step hydrothermal reaction and molding of a high energy ball milled slurry of fly ash, sodium bentonite, calcium hydroxide, and sodium water glass, followed by drying at ambient pressure. The monolith was characterized by XRD, FTIR, TG-DSC, SEM, TEM, BET, mercury porosimeter, and AFM. The addition of both sodium bentonite and sodium water glass plays a crucial role in preventing shrinkage and improving the porosity of the monolith. The monolith has the microstructure of randomly oriented and multually interwoven aluminum tobermorite nanosheets among which there are numerous macropores. Interestingly, the aluminum tobermorite nanosheets can be exfoliated by ultrasonication treatment to provide single-layer ultrathin nanosheets of aluminum tobermorite with a thickness of 1.18 nm and an aspect ratio of ∼1000. The monolith of aluminum tobermorite nanosheets has low apparent density (0.077 g cm^–3) and very low thermal conductivity (0.03793 W m^–1 K^–1). The low thermal conductivity of the monolith is attributed to its high porosity or pore volume due to the presence of numerous macropores among aluminum tobermorite nanosheets

Tuning the K⁺ Concentration in the Tunnel of OMS‑2 Nanorods Leads to a Significant Enhancement of the Catalytic Activity for Benzene Oxidation

OMS-2 nanorods with tunable K⁺ concentration were prepared by a facile hydrothermal redox reaction of MnSO₄, (NH₄)₂S₂O₈, and (NH₄)₂SO₄ at 120 °C by adding KNO₃ at different KNO₃/MnSO₄ molar ratios. The OMS-2 nanorod catalysts are characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption and desorption, inductively coupled plasma, and X-ray photoelectron spectrometry. The effect of K⁺ concentration on the lattice oxygen activity of OMS-2 is theoretically and experimentally studied by density functional theory calculations and CO temperature-programmed reduction. The results show that increasing the K⁺ concentration leads to a considerable enhancement of the lattice oxygen activity in OMS-2 nanorods. An enormous decrease (Δ<i><i>T</i></i>₅₀ = 89 °C; Δ<i>T</i>₉₀ > 160 °C) in reaction temperatures <i>T</i>₅₀ and <i>T</i>₉₀ (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation has been achieved by increasing the K⁺ concentration in the K⁺-doped OMS-2 nanorods due to the considerable enhancement of the lattice oxygen activity

Synergetic Effect between Photocatalysis on TiO₂ and Thermocatalysis on CeO₂ for Gas-Phase Oxidation of Benzene on TiO₂/CeO₂ Nanocomposites

TiO₂/CeO₂ nanocomposites of anatase TiO₂ nanoparticles supported on microsized mesoporous CeO₂ were prepared and characterized by SEM, TEM, BET, XRD, Raman, XPS, and diffuse reflectance UV–vis absorption. The formation of the TiO₂/CeO₂ nanocomposites considerably enhances their catalytic activity for the gas-phase oxidation of benzene, one of the hazardous volatile organic compounds (VOCs), under the irradiation of a Xe lamp compared to pure CeO₂ and TiO₂. A solar-light-driven thermocatalysis on CeO₂ is found for the TiO₂/CeO₂ nanocomposites. There is a synergetic effect between the photocatalysis on TiO₂ and the thermocatalysis on CeO₂ for the TiO₂/CeO₂ nanocomposites, which significantly increases their catalytic activity. The CO₂ formation rate (<i>r</i>_CO2) of the TiO₂/CeO₂ nanocomposite with the Ti/Ce molar ratio of 0.108 under the synergetic photothermocatalytic condition is 36.4 times higher than its <i>r</i>_CO₂ under the conventional photocatalytic condition at near room temperature. CO temperature-programmed reduction (CO-TPR) with the irradiation of the Xe lamp and in the dark reveals that the synergetic effect, which occurs at the interface of the TiO₂/CeO₂ nanocomposite, is due to the considerable promotion of the CeO₂ reduction by the photocatalysis on TiO₂

High Verdet Constant Glass for Magnetic Field Sensors

Due to the high transparency, high Verdet constant, as well as easy processing properties, rare-earth ion-doped glasses have demonstrated great potential in magneto-optical (MO) applications. However, the variation in the valence state of rare-earth ions (Tb3+ to Tb4+) resulted in the decreased effective concentration of the paramagnetic ions and thus degraded MO performance. Here, a strategy was proposed to inhibit the oxidation of Tb3+ into Tb4+ as well as improve the thermal stability by tuning the optical basicity of glass networks. Moreover, the depolymerization of the glass network was modulated to accommodate more Tb ions. Thus, a record high effective concentration (14.19 × 1021/cm3) of Tb ions in glass was achieved, generating a high Verdet constant of 113 rad/(T·m) at 650 nm. Lastly, the first application of MO glass for magnetic field sensors was demonstrated, achieving a sensitivity of 0.139 rad/T. We hope our work provides guidance for the fabrication of MO glass with high performance and thermal stability and could push MO glass one step further for magnetic sensing applications

Ice–Water Quenching Induced Ti³⁺ Self-doped TiO₂ with Surface Lattice Distortion and the Increased Photocatalytic Activity

The present research reported a facile strategy to prepare Ti³⁺ self-doped TiO₂ with increased photocatalytic activity. The TiO₂ subjected to high temperature preannealing was directly thrown into ice–water for rapid quenching. It is interesting to see that the quenched samples show pale blue color due to the absorption in visible and near-IR region. The comprehensive analyses of X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field-emission scanning electron microscope, and Brunauer–Emmett–Teller (BET) show that the crystallinity, the morphologies, and the specific surface area are almost unchanged after the ice–water quenching. The spectroscopic analyses of UV–vis diffusion reflectance spectra, photoluminescence spectra, and X-ray photoelectron spectra clearly show the change of electronic structure of TiO₂ due to presence of Ti³⁺ ions induced by the ice–water quenching, which is further confirmed by the electron paramagnetic resonance analysis. No Ti^3<b>+</b> ions are generated if the preannealing temperature is below 800 °C. The energy band structure model involving the Ti³⁺ ions and the associated oxygen defects was proposed to explain the change of UV–vis diffusion absorption. It is considered that the high concentration of oxygen defects at high preannealing temperatures can be partially frozen by the ice–water quenching, which then can denote the high concentration of excess electrons. Some excess electrons can be localized at Ti lattice sites, resulting in the presence of Ti³⁺ ions. More interestingly, it is also seen that the rapid ice–water quenching causes the distortion of surface lattice due to the interaction between hot TiO₂ and water, which tends to be poly crystalline and disordered for high preannealing temperature. The surface lattice distortion is considered to be correlated with the generation of oxygen defects during the ice–water quenching. The quenched samples show obviously increased photocatalytic activity for both methylene blue degradation and hydrogen evolution under UV light illumination. Although they do not have visible activity, loading amorphous Cu­(OH)_<i>x</i> nanoclusters can greatly increase their ability to degrade methylene blue under visible light illumination. It is also shown that the photocatalytic activity of ZnO can also be increased to some extent by the ice–water quenching. Therefore, the ice–water quenching could be a general method for increasing the photocatalytic activity of many materials