Latest ArticlesManganese dioxide (MnO2), a commonly find oxidant in both natural environment and industrial application, plays a crucial role for various organic compound degradation. Tuning the MnO2 crystal structure is a cost-effective strategy to boost the oxidation reactions, where the challenge remains due to lacking in-depth investigation of the crystal properties. Herein, MnO2 with different crystalline structures (x-MnO2) including α-, β- and δ- was prepared through the hydrothermal synthesis for a typical organic pollutant removal. The structural and degradation analysis indicated that the oxidation capacity was originated from Mn3+ and oxygen vacancies (OVs). The intrinsic relationships between oxidation performance and other physiochemical properties such as morphology and electrochemistry were thoroughly discussed, and positive correlations between oxidation capacity and electrochemical properties were found which eventually led to excellent oxidation performance via modulating the above-mentioned properties. Moreover, the K+ content was determined to be the most crucial role in manipulating the structure properties. This work offers a crystal-level insight into the relationship between the crystal structure and oxidative property, promoting rational design of highly efficient oxidant.
We present the synthesis, characterization and photoluminescence properties of uranium-containing selenotungstate, [(UO2)3(SeO3)3Na5(H2O)6(SeW6O21)(SeW9O33)3]21–, which was isolated by a one-pot reaction of uranium nitrate with sodium tungstate and sodium selenite in a pH 5.2 aqueous solution at 90 ℃. In this study, the effect of the introduction of lone-electron pair containing heteroatoms on the structure is demonstrated, a three-layered heterometallic {Se3U3Na5} cluster is encapsulated by two different anionic building block units: three trivacant Keggin {B-α-SeW9O33} and one Anderson {SeW6O21}. To our knowledge, the {Se3U3Na5} cluster has never been observed in the polyoxometalate chemistry. The solid-state photoluminescence properties and lifetime decay behaviours of the title compound (1) have been measured at room temperature, and the photoluminescence spectrum displays the characteristic emission bands of corresponding uranyl cations. In addition, the photoluminescence quantum yield of 1 is 72%, which is almost three times that of starting material UO2(NO3)2.6H2O (27%). By using this strategy, we envision that an increasing number of assemblies with 'open' clusters may be designed and obtained, in which the exposed oxygen atoms show strong affinity towards metal ions, providing new opportunities to generate bigger clusters or to tune existing properties.
Although converting the greenhouse gasses carbon dioxide (CO2) into solar fuels is regarded as a convenient means of solar energy storage, the intrinsic mechanism on how the high chemical inertness linear CO2 molecules is activated and converted on a semiconductor oxide is still elusive. Herein, by creating the oxygen vacancies on the typical hexagonal tungsten oxide (WO3), we realize the continuous photo-induced CO2 reduction to selectively produce CO under light irradiation, which was verified by isotope labeling experiment. Detailed oxygen vacancies evolution investigation indicates that light irradiation can simultaneously induce the in-situ formation of oxygen vacancies on hexagonal WO3, and the oxygen vacancies promote the adsorption and activation of CO2 molecules, leading to the CO2 reduction to CO on the hexagonal WO3 via an oxygen vacancies-involved process. Besides, the existence of water further promotes the formation of CO2 reduction intermediate, further promote the CO2 photoreduction. Our work provides insight on the mechanism for converting CO2 into CO under light irradiation.
The cycloaddition reactions of methane and ethylene mediated by Ir+ have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations. Studies have shown that Ir+ can mediate the cycloaddition reaction of CH4 and two C2H4 to generate a half-sandwich structure IrHCp+ (Cp = η5-C5H5) including pentamethylcyclopentadienyl ligand by continuous dehydrogenation reaction with the forming of three C-C bonds and seven C-H bonds. The orbital analysis indicates the mechanism of the cyclization reaction to generation of pentamethylcyclopentadienyl ligand with odd number carbon atom depends on the overlap of π orbitals in -C2H2 and carbene, which is more difficult than the forming of cyclobutadiene ligand and benzene. This study may help to understand the reaction mechanism in the cycloaddition reactions of organic compounds, which will be useful to guide the rational design of new catalysts with tailored selectivity and increased efficiency.
Efficient CO2 reduction reaction (CO2RR) is one of the important topics in energy and environment field, but improving the electrochemical selectivity of specific product is a great challenge. Herein, we reported a unprecedented two-dimensional (2D) metal−organic framework with CuO4 unit (denoted as Cu-HHTT, HHTT = 9, 10-dihydro-9, 10-[1,2]benzenoanthracene-2, 3, 6, 7, 14, 15-hexaol) as the electrocatalyst for CO2RR. Cu-HHTT exhibits high performance for CO2RR to produce CO, namely Faradaic efficiency of 96.6% toward CO with a current density of 18 mA/cm2 at the potential of −0.6 V vs. RHE. Density function theory reveals that the desorption of CO species exhibits a lower energy barrier than that of hydrogenation of *CO intermediate, resulting in CO as the main product instead of alcohols or hydrocarbons.
The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in the renewable energy. Generally, ZrO2 was regarded as an inferior support for Ru catalyst used in ammonia synthesis. Here we prepare ZrO2 with monoclinic phase and carbon species from ZrCl4 following the preparation route of UiO-66 as well as ammonia treatment. Owing to the presence of a larger amount of hydrogen adsorption as well as the easier desorption of hydrogen species, the ill effect of hydrogen species on the nitrogen adsorption-desorption and ammonia synthesis can be effectively alleviated. The resulting ZrO2-supported Ru catalyst showed 4 times higher ammonia synthesis activity than the conventional Ru/ZrO2 obtained from zirconium nitrate.
Application of Li-oxygen (Li-O2) battery is in urgent need of bifunctional ORR/OER electrocatalyst. A surface-functionalization CoP/Ti3C2Tx composite was fabricated theoretically, with the optimized electronic structure and more active electron, which is beneficial to the electrochemical reaction. The accordion shaped Ti3C2Tx is featured with large specific surface area and outstanding electronic conductivity, which is beneficial for the adequate exposure of active sites and the deposition of Li2O2. Transition metal phosphides provide more electrocatalytic active sites and present good electrocatalytic effect. The CoP/Ti3C2Tx composite served as the electrocatalyst of Li-O2 battery reaches a high specific discharge capacity of 17, 413 mAh/g at 100 mA/g and the lower overpotential of 1.25 V, superior to those of the CoP and Ti3C2Tx individually. The composite of transition metal phosphides and MXene are applied in Li-O2 battery, not only demonstrating higher cycling stability of the prepared CoP/Ti3C2Tx composite, but pointing out the direction for their electrochemical performance improvement.
Supercapacitors (SCs) are rated as the foremost efficient devices bridging the production and consumption of renewable energy. To address the ever-increasing energy requirements, it is indispensable to further develop high-performance SCs with merits of high energy-density, acceptable price and long-term stability. This review highlights the recent advances on halogen-based functionalized chemistry engineering in the state-of-the-art electrode system for high-performance SCs, primarily referring to the doping and decoration strategies of F, Cl, Br and I elements. Due to the discrepancy of electronegativity and atomic radius, the functionalization of each halogen element endows the substrate materials with different physicochemical properties, including energy bandgap structure, porosity distribution and surface affinity. The principle of halogen embedment into host materials by precisely controlling ionic adsorption and electronic structure is presented. And, the vital perspectives on the future challenges of halogen functionalization are also discussed. This work aims to deepen the understanding of halogen-based functionalized strategies to motivate further research for the development of high-performance SCs, and it also provides a prospect for exploring new material modification methods for electrochemical energy storage.
Developing non-conjugated luminescent polymers (NCLPs) with fluorescence and long-lived room-temperature phosphorescence is of great significance for revealing the essence of NCLPs luminescence, which has gradually attracted the attention of researchers in recent years. Herein, polymethylol (PMO) and poly(3-butene-1, 2-diol) (PBD) with polyhydroxy structures were prepared and their luminescence behaviors were investigated to reveal the clusteroluminescence (CL) mechanism. Compared with polyvinyl alcohol with non-luminescent behavior, PMO and PBD exhibit cyan-blue fluorescence with quantum yields of ca. 12% and green room-temperature phosphorescence with lifetimes of ca. 89 ms in the solid state. Both fluorescence and phosphorescence exhibit typical excitation-dependent CL behavior. Experimental and theoretical analyses show that the strong hydrogen-bonding interaction of PMO and PBD greatly promotes the formation of oxygen clusters and the through-space n-n interaction of oxygen atoms, enabling fluorescence and phosphorescence emission. Our results have enormous implications for understanding the CL mechanism of NCLPs and provide a new polymer design strategy for the rational design of novel NCLPs materials.
The SARS-CoV-2 virus is released from an infectious source (such as a sick person) and adsorbed on aerosols, which can form pathogenic microorganism aerosols, which can affect human health through airborne transmission. Efficient sampling and accurate detection of microorganisms in aerosols are the premise and basis for studying their properties and evaluating their hazard. In this study, we built a set of sub-micron aerosol detection platform, and carried out a simulation experiment on the SARS-CoV-2 aerosol in the air by wet-wall cyclone combined with immunomagnetic nanoparticle adsorption sampling and ddPCR. The feasibility of the system in aerosol detection was verified, and the influencing factors in the detection process were experimentally tested. As a result, the sampling efficiency was 29.77%, and extraction efficiency was 98.57%. The minimum detection limit per unit volume of aerosols was 250 copies (102 copies/mL, concentration factor 2.5).
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