Homogeneous Catalytic Process of a Heterogeneous Ru Catalyst in Li–O₂ via X‑ray Nanodiffraction Observation

In recent years, lithium oxygen batteries (Li–O2) have received considerable research attention due to their extremely high energy density. However, the poor conductivity and ion conductivity of the discharge product lithium peroxide (Li2O2) result in a high charging overpotential, poor cycling stability, and low charging rate. Therefore, studying and improving catalysts is a top priority. This study focuses on the commonly used heterogeneous catalyst ruthenium (Ru). The local distribution of this catalyst is controlled by using sputtering technology. Moreover, X-ray nanodiffraction is applied to observe the relationship between the decomposition of Li2O2 and the local distribution of Ru. Results show that Li2O2 decomposes homogeneously in liquid systems and heterogeneously in solid-state systems. This study finds that the catalytic effect of Ru is related to electrolyte decomposition and that its soluble byproducts act as electron acceptors or redox mediators, effectively reducing charging overpotential but also shortening the cycle life

High-Performance Lithium-Ion Battery and Symmetric Supercapacitors Based on FeCo₂O₄ Nanoflakes Electrodes

A successive preparation of FeCo₂O₄ nanoflakes arrays on nickel foam substrates is achieved by a simple hydrothermal synthesis method. After 170 cycles, a high capacity of 905 mAh g^–1 at 200 mA g^–1 current density and very good rate capabilities are obtained for lithium-ion battery because of the 2D porous structures of the nanoflakes arrays. The distinctive structural features provide the battery with excellent electrochemical performance. The symmetric supercapacitor on nonaqueous electrolyte demonstrates high specific capacitance of 433 F g^–1 at 0.1 A g^–1 and 16.7 F g^–1 at high scan rate of 5 V s^–1 and excellent cyclic performance of 2500 cycles of charge–discharge cycling at 2 A g^–1 current density, revealing excellent long-term cyclability of the electrode even under rapid charge–discharge conditions

CoSe₂ Embedded in C₃N₄: An Efficient Photocathode for Photoelectrochemical Water Splitting

An efficient H₂ evolution catalyst is developed by grafting CoSe₂ nanorods into C₃N₄ nanosheets. The as-obtained C₃N₄–CoSe₂ heterostructure can show excellent performance in H₂ evolution with outstanding durability. To generate phatocathode for photoelectrochemical water splitting CoSe₂ grafted in C₃N₄ was decorated on the top of p-Si microwires (MWs). p-Si/C₃N₄–CoSe₂ heterostructure can work as an efficient photocathode material for solar H₂ production in PEC water splitting. In 0.5 M H₂SO₄, p-Si/C₃N₄–CoSe₂ can afford photocurrent density −4.89 mA/cm² at “0” V vs RHE and it can efficiently work for 3.5 h under visible light. Superior activity of C₃N₄–CoSe₂ compared to CoSe₂ toward H₂ evolution is explained with the help of impedance spectroscopy

All-Solid-State Li-Ion Battery Using Li_1.5Al_0.5Ge_1.5(PO₄)₃ As Electrolyte Without Polymer Interfacial Adhesion

Solid-state lithium-ion batteries are promising candidates for energy storage devices that meet the requirements to reduce CO₂ emissions. NASICON-type solid-state electrolytes (SSE) are most promising materials as electrolytes for high-performance lithium ion batteries because of their good stability and high ionic conductivity. In this study, we successfully fabricate NASICON-based Li_1.5Al_0.5Ge_1.5(PO₄)₃ lithium fast-ion conductors through melt-quenching with post-crystallization. The effect of crystallization temperature on the structure of LAGP and their ionic conductivity is systematically studied using Rietveld analysis of Synchrotron X-ray powder diffraction patterns, multinuclear magnetic resonance, and electrochemical analysis, revealing that the mobility of Li ion is dependent on crystallization temperature. The glass–ceramic LAGP annealed at 800 °C for 8 h exhibits the highest conductivity of 0.5 mS cm^–1 at room temperature. Moreover, we report the viability of the prepared LAGP glass−ceramic as a solid electrolyte in Li-ion batteries without polymer adhesion. The cycling of Li/LAGP/LFP all-solid-state cell, provides a stable cycling lifetime of up to 50 cycles. This approach demonstrates that LAGP glass–ceramic can have good contact with the electrodes without interfacial layer and can deliver a reasonable discharge capacity after 50 cycles

Wide Range pH-Tolerable Silicon@Pyrite Cobalt Dichalcogenide Microwire Array Photoelectrodes for Solar Hydrogen Evolution

This study employed silicon@cobalt dichalcogenide microwires (MWs) as wide range pH-tolerable photocathode material for solar water splitting. Silicon microwire arrays were fabricated through lithography and dry etching technologies. Si@Co­(OH)₂ MWs were utilized as precursors to synthesize Si@CoX₂ (X = S or Se) photocathodes. Si@CoS₂ and Si@CoSe₂ MWs were subsequently prepared by thermal sulfidation and hydrothermal selenization reaction of Si@Co­(OH)₂, respectively. The CoX₂ outer shell served as cocatalyst to accelerate the kinetics of photogenerated electrons from the underlying Si MWs and reduce the recombination. Moreover, the CoX₂ layer completely deposited on the Si surface functioned as a passivation layer by decreasing the oxide formation on Si MWs during solar hydrogen evolution. Si@CoS₂ photocathode showed a photocurrent density of −3.22 mA cm^–2 at 0 V (vs RHE) in 0.5 M sulfuric acid electrolyte, and Si@CoSe₂ MWs revealed moderate photocurrent density of −2.55 mA cm^–2. However, Si@CoSe₂ presented high charge transfer efficiency in neutral and alkaline electrolytes. Continuous chronoamperometry in acid, neutral, and alkaline solutions was conducted at 0 V (vs RHE) to evaluate the photoelectrochemical durability of Si@CoX₂ MWs. Si@CoS₂ electrode showed no photoresponse after the chronoamperometry test because it was etched through the electrolyte. By contrast, the photocurrent density of Si@CoSe₂ MWs gradually increased to −5 mA cm^–2 after chronoamperometry characterization owing to the amorphous structure generation

Controlling The Activator Site To Tune Europium Valence in Oxyfluoride Phosphors

A new Eu³⁺-activated oxyfluoride phosphor Ca₁₂Al₁₄O₃₂F₂:Eu³⁺ (CAOF:Eu³⁺) was synthesized by a solid state reaction. Commonly red line emission was detected in the range of 570–700 nm. To achieve the requirement of illumination, this study revealed a crystal chemistry approach to reduce Eu ions from 3+ to 2+ in the lattice. Replacing Al³⁺–F^– by the appreciate dopant Si⁴⁺–O^2– is adopted to enlarge the activator site that enables Eu³⁺ to be reduced. The crystallization of samples was examined by powder X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Photoluminescence results indicated that as-synthesized phosphors Ca₁₂Al_{14‑<i>z</i>}Si_<i>z</i>O_32+<i>z</i>F_2–<i>z</i>:Eu (<i>z</i> = 0–0.5, CASOF:Eu) display an intense blue emission peaking at 440 nm that was produced by 4f–5d transition of Eu²⁺, along with the intrinsic emission of Eu³⁺ under UV excitation. Moreover, the effect of Si⁴⁺–O^2– substitution involved in the coordination environment of the activator site was investigated by further crystallographic data from Rietveld refinements. The ¹⁹F solid-state nuclear magnetic resonance (NMR) data were in agreement with refinement and photoluminescence results. Furthermore, the valence states of Eu in the samples were analyzed with the X-ray absorption near edge structure (XANES). The quantity of substituted Si⁴⁺–O^2– tunes chromaticity coordinates of Ca₁₂Al_{14–<i>z</i>}Si_<i>z</i>O_32+<i>z</i>F_2–<i>z</i>:Eu phosphors from (0.6101, 0.3513) for <i>z</i> = 0 to (0.1629, 0.0649) for <i>z</i> = 0.5, suggesting the potential for developing phosphors for white light emitting diodes (WLEDs). Using an activator that is valence tunable by controlling the size of the activator site represents a hitherto unreported structural motif for designing phosphors in phosphor converted light emitting diodes (pc-LEDs)

Chitosan-Modified Stable Colloidal Gold Nanostars for the Photothermolysis of Cancer Cells

The preparation and properties of plasmonic gold nanostars (Au NSs) modified with a biopolymer chitosan are reported. The colloidal stability of Au NSs at the physiological pH of 7.5 and their performance in the photothermolysis of cancer cells in vitro were compared with those of gold nanorods (Au NRs). The optical characteristics of chitosan-modified Au NSs dispersed in a medium with pH = 7.5 had higher stability than those of chitosan-capped NRs because of the slower aggregation of NSs. At pH = 7.5, the chitosan-modified Au NRs formed aggregates with highly nonuniform sizes. On the other hand, Au NSs formed small chain-like clusters, in which individual NSs were connected to one another, preferably via association of branches with central cores. It is possible that the difference in areal charge density at these parts of NSs is responsible for their preferred association. Flow cytometry analysis showed the relatively nonequivalent distribution of the chitosan-capped Au NRs across the cell line compared with that of Au NSs because of the fast and nonuniform aggregation of NRs. An in-vitro photothermolysis experiment on J5 cancer cells showed that energy fluences of 23 and 33 mJ/cm² are necessary to cause complete death of J5 cells incubated with 4 μg/mL chitosan-capped Au NSs and NRs, respectively. When chitosan was used as a surface-capping agent, the Au NSs exhibited higher colloidal stability at the physiological pH than the NRs and lower energy fluence necessary for cell photothermolysis because of more uniform cellular uptake