A novel way to grow MoS2 on a large scale with uniformity and in desired patterns is developed. We use Au film as a catalyst on which Mo(CO)6 vapor decomposes to form a Mo‐Au surface alloy that is an ...ideal Mo reservoir for the growth of atomic layers of MoS2. Upon exposure to H2S, this surface alloy transforms into a few layers of MoS2, which can be isolated and transferred on an arbitrary substrate. By simply patterning Au catalyst film by conventional lithographic techniques, MoS2 atomic layers in desired patterns can be fabricated.
When a gold surface reacts with vaporized Mo(CO)6 at 300 °C, a surface alloy forms, which in turn becomes an ideal large‐scale atom‐thick Mo reservoir. When this alloy further reacts with H2S, atomic layers of MoS2 are specifically formed on Au, which can be isolated by means of etching.
Singlet oxygen (1O2) is one of the most critical species leading to parasitic side reactions and poor reversibility in non‐aqueous Li−O2 batteries. 1O2 is generated via the disproportionation of the ...superoxide radical (O2.−) in O2/Li2O2 electrochemistry. The mechanistic and computational studies on 1O2 formation revealed the significant roles of the associated cations, solvation ability of aprotic solvents, H+ source, and catalyst/electrode materials. Along with efforts to alleviate 1O2 production, trapping and eliminating 1O2 have been attempted using molecular agents. Anthracene derivatives trap 1O2 and form endoperoxides, which can be quantitatively detected using in situ fluorescence analysis. Physical quenchers that convert 1O2 to 3O2 are desirable for cycling of Li−O2 cells because quencher molecules are reusable. We highlight the recent reports on the formation and elimination of 1O2, and challenges and perspectives of suppressing the 1O2 effect on the performance of Li−O2 cells.
The limiting species: Singlet oxygen (1O2) is one of the critical species leading to side reactions and poor cyclability of non‐aqueous Li−O2 battery. This minireview covers recent achievements on the major factors determining 1O2 formation and development of 1O2 trapping/quenching agents for improving the reversibility of Li−O2 electrochemistry.
We studied solid electrolyte interphase (SEI) on metallic sodium (Na) electrodes. Among sodium hexafluorophosphate (NaPF6), sodium triflate (NaOTf), and sodium bis(trifluoromethanesulfonyl)imide ...(NaTFSI) electrolytes, sodium fluoride (NaF)‐rich and compact SEI was only formed by chemical reduction of NaPF6. Excellent rigidity and insolubility of NaF‐rich SEI layer enhanced electrochemical cycling performances for both Na/Na symmetric cells and sodium–oxygen (Na–O2) cells. By contrast, the Na electrodes using NaOTf and NaTFSI formed porous and carbonaceous SEI layers rather than NaF. Soluble carbonaceous species were detached from the Na electrode, which led to the undesired decomposition of electrolyte solution. It resulted in the substantial formation of the dead Na and dendritic Na and caused cycling failure of Na–O2 cells within 10 cycles, demonstrated by NaOTf.
Studies of solid electrolyte interface of Na metals and their effects for Na/Na nad Na–O2 cell performances.
Synthesis of morphologically well-defined crystals of metalloporphyrin by direct crystallization based on conventional anti-solvent crystallization method without using any additives has been rarely ...reported. Herein, we demonstrate an unconventional and additive-free synthetic method named reverse anti-solvent crystallization method to achieve well-defined zinc-porphyrin cube crystals by reversing the order of the addition of solvents. The extended first solvation shell effect mechanism is therefore suggested to support the synthetic process by providing a novel kinetic route for reaching the local supersaturation environment depending on the order of addition of solvents, which turned out to be critical to achieve clean cube morphology of the crystal. We believe that our work not only extends fundamental knowledge about the kinetic process in binary solvent systems, but also enables great opportunities for shape-directing crystallization of various organic and organometallic compounds.
The review describes electrochemical applications of tip-enhanced Raman spectroscopy (TERS). These applications combine the merits of both scanning probe microscopy (SPM) and Raman spectroscopy, ...which enables us to simultaneously obtain high-resolution images of surface morphology and chemical information under the electrochemical environment. This review, first summarizes the pioneering work done on the TERS systems that operate in liquid and electrochemical environments, and then gives an overview of the typical instrumentation of electrochemical TERS (EC-TERS) based on electrochemical scanning tunneling microscopy (EC-STM). Furthermore, this review summarizes the advancements in EC-TERS studies of events that occur at the interfaces. These include potential dependent structural changes and electrochemical reactions. Finally, we discuss the current issues and future prospects of EC-TERS for microscopic studies of electrochemical interfaces.
We report the tubular shape of molybdenum sulfide selenide (MoSSe) alloy on the carbon nanotubes (CNTs) as lithium (Li) storage materials. Two to five layers of MoSSe alloy have an interlayer spacing ...of ~6.6 Å and coaxially coat the CNT. After Li ion is intercalated to the MoSSe layers, Li2S, Li2Se, and metallic Mo nanoparticles are irreversibly deposited on the CNT electrodes by a chemical conversion process. Galvanostatic cycling tests perform Li2S/Li2Se faradaic reaction at ~2.2 V vs. Li/Li+ and capacitive processes below ~1.3 V arising from physical adsorption of Li+ on Mo, Li2S, and Li2Se nanoparticles, and electrolyte decomposition. As a result, tubular MoSSe/CNT electrodes exhibit stable cyclability for over 200 cycles, the capacity of 663 mAh g−1, and excellent rate capability that is two-fold greater at 20 A g−1 than that of the MoS2 sheet partially wrapping the CNT. It is attributed to stable Li2S/Li2Se redox reaction without any dissolution of polysulfides/polyselenides, respectively, low charge-transfer resistance, and retardation of electrolyte decomposition. These findings suggest that the tubular MoSSe/CNT nanocomposites act as promising electrodes for hybrid-ion capacitors.
White light‐emitting phenothiazine‐poly(dimethylsiloxane) (PTZ–PDMS) composites are formed by a photooxidation reaction. The oxidized PTZ species, i.e., PTZ cation radicals and dication species, are ...created by electron transfer from the PTZ molecules to PDMS under UV irradiation. In situ UV–vis and electron spin resonance (ESR) spectroscopies are carried out after UV exposure of PTZ–PDMS, and the results provide evidence for the spontaneous ionization of PTZ. The spectral changes indicate the formation of PTZ•+ (radical cation) and PTZ2+ (dication) within the PDMS matrix. Moreover, a combination of PTZ, PTZ•+, and PTZ2+, together with the PDMS matrix, show an unexpected emission of white light with Commission Internationale de L'Eclairage coordinates of 0.34 and 0.32, which are close to those of pure white light. These findings potentially offer a new route and strategy for the development of flexible white light‐emitting materials.
Single‐component white light emitters! White light‐emitting phenothiazine–poly(dimethylsiloxane) (PTZ–PDMS) composites are prepared by photooxidation in air. Only the PTZ–PDMS composites prepared by photooxidation in air emit white photoluminescent light under UV irradiation, and the oxidized PTZ show high stability within the PDMS matrix.
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