The practical application of the lithium–sulfur (Li–S) battery is seriously restricted by its shuttle effect, low conductivity, and low sulfur loading. Herein, first‐principles calculations are ...conducted to verify that the introduction of oxygen vacancies in TiO2 not only enhances polysulfide adsorption but also greatly improves the catalytic ability and both the ion and electron conductivities. A commercial polypropylene (PP) separator decorated with TiO2 nanosheets with oxygen vacancies (OVs‐TiO2@PP) is fabricated as a strong polysulfide barrier for the Li–S battery. The thickness of the OVs‐TiO2 modification layer is only 500 nm with a low areal mass of around 0.12 mg cm−2, which enhances the fast lithium‐ion penetration and the high energy density of the whole cell. As a result, the cell with the OVs‐TiO2@PP separator exhibits a stable electrochemical behavior at 2.0 C over 500 cycles, even under a high sulfur loading of 7.1 mg cm−2, and an areal capacity of 5.83 mAh cm−2 remains after 100 cycles. The proposed strategy of engineering oxygen vacancies is expected to have wide applications in Li–S batteries.
Introducing oxygen vacancies into TiO2 can promote the commercial polypropylene (PP) separator (OVs‐TiO2@PP) as a robust barrier for inhibiting the shuttle effect and facilitating polysulfide conversion. The proposed functional separator promotes the development potential of oxygen vacancies in high‐energy‐density Li–S batteries.
Carbon‐based nanomaterials have been widely utilized in catalysis and energy‐related fields due to their fascinating properties. However, the controllable synthesis of porous carbon with refined ...morphology is still a formidable challenge due to inevitable aggregation/fusion of resulted carbon particles during the high‐temperature synthetic process. Herein, a hierarchically oriented carbon‐structured (fiber‐like) composite is fabricated by simultaneously taking advantage of a confined pyrolysis strategy and disparate bond environments within metal–organic frameworks (MOFs). In the resultant composite, the oriented carbon provides a fast mass (molecule/ion/electron) transfer efficiency; the doping‐N atoms can anchor or act as active sites; the mesoporous SiO2 (mSiO2) shell not only effectively prevents the derived carbon or active metal nanoparticles (NPs) from aggregation or leaching, but also acts as a “polysulfide reservoir” in the Li–S batteries to suppress the “shuttle” effect. Benefiting from these advantages, the synthesized composite Pd@NDHPC@mSiO2 (NDHPC means N‐doped hierarchically porous carbon) exhibits extremely high catalytic activity and stability toward the one‐pot Knoevenagel condensation–hydrogenation reaction. Furthermore, the oriented NDHPC@mSiO2 manifests a boosted capacity and cycling stability in Li–S batteries compared to the counterpart that directly pyrolyzes without silica protection. This report provides an effective strategy of fabricating hierarchically oriented carbon composites for catalysis and energy storage applications.
An N‐doped oriented carbon‐structured (fiber‐like) composite with hierarchical pore and ultrafine Pd nanoclusters is fabricated by simultaneously taking advantage of the confined pyrolysis strategy and disparate bond environments within metal–organic frameworks (MOFs). The synthesized composite Pd@NDHPC@mSiO2 manifests extremely high catalytic activity toward tandem catalysis and much boosted cycling stability in Li–S batteries.
Flaky and nanospherical birnessite and birnessite-supported Pt catalysts were successfully prepared and characterized by means of Xray diffraction （XRD）,transmission electron microscopy （TEM）,energy ...dispersive spectroscopy （EDS） and N2 adsorption-desorption.Effects of the birnessite morphology and Pt reduction method on the catalytic activity for the complete oxidation of formaldehyde （HCHO） were investigated.It was found that flaky birnessite exhibited higher catalytic activity than nanospherical birnessite.The promoting effect of Pt on the birnessite catalyst indicated that the reduction method of the Pt precursor greatly influenced the catalytic performance.Flaky birnessite-supported Pt nanoparticles reduced by KBH 4 showed the highest catalytic activity and could completely oxidize HCHO into CO2 and H2O at 50℃,whereas the sample reduced using H2-plasma showed lower activity for HCHO oxidation.The differences in catalytic activity of these materials were jointly attributed to the effects of pore structure,surface active sites exposed to HCHO and the dispersion of Pt nanoparticles.
Editor＇s comments Formaldehyde （HCHO） emitted from chemical manufacturing plants including methanol-gasoline/diesel fuel vehicles and the construction and decoration materials is one of the major air ...pollutions, which induces photochemical pollution and hazards human health. Great efforts have been made for the reduction or control of the emission of HCHO to satisfy the stringent environmental regulations. Now, a new study supported by the National Natural Science Foundation of China reports mesoporous manganese oxide with novel nanostructures for the decomposition of HCHO. The obtained manganese oxide nanomaterials showed high catalytic activities for oxidative decomposition of HCHO at low temperatures. Complete conversion of HCHO to CO2 and H2O were achieved, and no harmful by- products were detected in effluent gases. The catalytic activities of these nanomaterials are significantly higher than those of previously reported manganese oxide octahedral molecular sieve （OMS-2） nanorods , MnO x powders, and alumnina-supported mangnaese-palladium oxide catalysts. These results provide a new route for the removal of HCHO and other air pollutions.
Cellulose has received a tremendous amount of attention both in academia and industry owing to its unique structural features, impressive physical–chemical properties, and wide applications. This ...natural polymer is originally used for packaging, paper, lightweight composites, and so forth and is now being developed for various new areas, such as antibacterial treatment, catalysis, water purification and separation, and biological and environmental analysis. In the current article, we summarize the recent developments in the self-assembly of cellulose with various species including metal ions and metal and metal oxide nanoparticles. Then we highlight several key application areas of cellulose-based composites by reviewing the recent representative literature in each area. A significant part of this review demonstrates some exciting innovations for a wide range of practical applications of cellulose-based composites. Some challenges are also discussed with a view toward future developments.
Fast, selective, and effective enrichment is critical for onsite detection and online monitoring of extremely low-concentration toxic heavy metal ions in complex environmental samples. In the current ...work, varied CuS nanostructures (hollow nanospheres, nanoflowers, nanoparticles) were prepared and applied to the enrichment of Hg(II) ions. Surprisingly, the as-prepared CuS nanostructures exhibited unprecedented ultrahigh selectivity and rapid uptake toward Hg(II) ions in the presence of other seven metal ions, suggesting specificity of mercury enrichment by the CuS nanostructures. Upon treating a 100 mL aqueous sample containing 8 different metal ions with only 10 mg of CuS hollow nanospheres, over 99.5% of Hg(II) ions could be removed within just 1 min, achieving a final Hg(II) ion level down to 0.1 ppb. This excellent selectivity was well accounted for by the Hard Soft Acid Base theory and especially the solubility product constant, where the solubility product constant of CuS is higher than that of HgS but lower than that of sulfides of other interfering metal ions. The current results are striking and would open a new avenue to the search for highly selective and efficient absorptive nanomaterials toward varied heavy metal ions.
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•CuS/cellulose composites were fabricated.•The Hg(II) adsorption capacity reached as high as 1040 mg g−1.•Fast adsorption kinetics, reaching the adsorption equilibrium in 30 s.•Unique ...selectivity to Hg(II) ions in presence of varied competing metal ions.•Application for portable enrichment and separation of Hg(II) ions.
This work demonstrates a novel nanomaterial for rapid, efficient and selective enrichment as well as portable separation of Hg(II) ions, which integrates the advantages of hydrophilic porous cellulose fibers and specific Hg(II) recognizing CuS nanoparticles. The optimal CuS/cellulose fibers nanomaterial (CC-60) exhibits a markedly faster adsorption rate, reaching adsorption equilibrium within 30 s, and a large Hg(II) uptake capacity as high as 1040 mg g−1 in 2 min. The distribution coefficient (Kd) of CC-60 for Hg(II) ions is four orders of magnitude higher than those for other common metal ions, thus giving unique selectivity for Hg(II) ions in the presence of other common metal ions. CC-60 can be used in portable column devices for the sequestration of Hg(II) ions from practical water samples, rapidly lowering the Hg(II) concentration from 16.6 mg L−1 to 9 μg L−1 in 5 s, which surpasses all those sulfur-based materials reported thus far. Such exciting properties are closely related to the synergistic effects arising from the porous structure and hydrophilicity of cellulose fibers, the unique recognition capability of CuS towards Hg(II), and the readily accessible CuS sites on cellulose fibers. This work would open up a new avenue to materials and devices for fast recognition, sequestration, enrichment and detection of Hg(II) as well as other toxic heavy metal ions.
Graphene-based hybrids for catalysis are currently attracting tremendous attention due to their unique and advantageous properties. However, the application in gas-phase thermal catalysis including ...the catalytic oxidation of volatile organic compounds (VOCs) remains a theoretical research stage. Here we developed a new use of graphene-based hybrid as a catalyst for formaldehyde (HCHO) oxidation. The hybrid design of MnO2 catalyst incorporated on graphene nanosheets not only exposes more active surface for catalysis, introduces expressways for charge travel during redox reaction, but also brings a large amount of surface OH– species, which simplifies the decomposition pathway of HCHO without the generation and oxidation of intermediate CO. Therefore, this hybrid design enables great performance enhancements in HCHO oxidation as compared to pure MnO2 and even other noble metal catalysts, displaying a much low 100% removal temperature of 65 °C. Highly stable performance and excellent recycling ability are also observed over graphene–MnO2 hybrids. Kinetic tests reveal that the introduction of graphene reduces activation energy of MnO2 catalyst from 65.5 to 39.5 kJ mol–1.
Podocyte injury is a major determinant of proteinuric kidney disease and the identification of potential therapeutic targets for preventing podocyte injury has clinical importance. Here, we show that ...histone deacetylase Sirt6 protects against podocyte injury through epigenetic regulation of Notch signaling. Sirt6 is downregulated in renal biopsies from patients with podocytopathies and its expression correlates with glomerular filtration rate. Podocyte-specific deletion of Sirt6 exacerbates podocyte injury and proteinuria in two independent mouse models, diabetic nephropathy, and adriamycin-induced nephropathy. Sirt6 has pleiotropic protective actions in podocytes, including anti-inflammatory and anti-apoptotic effects, is involved in actin cytoskeleton maintenance and promotes autophagy. Sirt6 also reduces urokinase plasminogen activator receptor expression, which is a key factor for podocyte foot process effacement and proteinuria. Mechanistically, Sirt6 inhibits Notch1 and Notch4 transcription by deacetylating histone H3K9. We propose Sirt6 as a potential therapeutic target for the treatment of proteinuric kidney disease.Podocytes are essential components of the renal glomerular filtration barrier and podocyte dysfunction leads to proteinuric kidney disease. Here Liu et al. show that Sirt6 protects podocytes from apoptosis and inflammation by increasing autophagic flux through inhibition of the Notch pathway.
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Although the mercury pollution is declining in the Western and European parts of the world, it is still a widespread environmental concern because of its notorious toxic effects on ...aquatic ecosystems and human health. Selective and rapid enrichment is essential for timely monitoring and efficient removal of trace mercury contaminants, but has so far been a big challenge. In the current work, we report a superparamagnetic molybdenum disulfide (Fe3O4@MoS2) with an expanded interlayer spacing (1.0 nm) and high magnetic susceptibility for highly selective and rapid uptake of Hg2+ ions. Upon treatment by Fe3O4@MoS2, over 99% of 15 ppm Hg2+ can be removed in 2 min from aqueous solutions, with an initial adsorption rate as high as 52.62 g mg−1 min−1. Fe3O4@MoS2 also demonstrate capability to efficiently enrich Hg2+ from samples with ppb levels of Hg2+, resulting in an ultralow residual Hg2+ concentration (60 ppt), which is far below the acceptable limit for drinking water (2 ppb). Fe3O4@MoS2 also shows high selectivity for Hg2+versus other eight representative metal ions. Furthermore, the selectivity for heavy metal ions can be optionally tailored by simply controlling the contact time during the uptake. This new finding is in contrast to the previously reported selectivity enhancement strategies by searching for new materials and chemical modification of adsorbents, and would enable additional improvement of selectivity by kinetic process engineering.
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