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Träfflista för sökning "WFRF:(Persson Per O. A.) ;pers:(Tao Quanzheng)"

Sökning: WFRF:(Persson Per O. A.) > Tao Quanzheng

  • Resultat 1-10 av 11
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1.
  • Persson, Ingemar, et al. (författare)
  • Tailoring Structure, Composition, and Energy Storage Properties of MXenes from Selective Etching of In-Plane, Chemically Ordered MAX Phases
  • 2018
  • Ingår i: Small. - : WILEY-V C H VERLAG GMBH. - 1613-6810 .- 1613-6829. ; 14:17
  • Tidskriftsartikel (refereegranskat)abstract
    • The exploration of 2D solids is one of our times generators of materials discoveries. A recent addition to the 2D world is MXenes that possses a rich chemistry due to the large parent family of MAX phases. Recently, a new type of atomic laminated phases (coined i-MAX) is reported, in which two different transition metal atoms are ordered in the basal planes. Herein, these i-MAX phases are used in a new route for tailoriong the MXene structure and composition. By employing different etching protocols to the parent i-MAX phase (Mo2/3Y1/3)(2)AlC, the resulting MXene can be either: i) (Mo2/3Y1/3)(2)C with in-plane elemental order through selective removal of Al atoms or ii) Mo1.33C with ordered vacancies through selective removal of both Al and Y atoms. When (Mo2/3Y1/3)(2)C (ideal stoichiometry) is used as an electrode in a supercapacitor-with KOH electrolytea volumetric capacitance exceeding 1500 F cm(-3) is obtained, which is 40% higher than that of its Mo1.33C counterpart. With H2SO4, the trend is reversed, with the latter exhibiting the higher capacitance (approximate to 1200 F cm(-3)). This additional ability for structural tailoring will indubitably prove to be a powerful tool in property-tailoring of 2D materials, as exemplified here for supercapacitors.
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2.
  • Qin, Leiqiang, et al. (författare)
  • A flexible semitransparent photovoltaic supercapacitor based on water-processed MXene electrodes
  • 2020
  • Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 8:11, s. 5467-5475
  • Tidskriftsartikel (refereegranskat)abstract
    • Solar energy, although it has the highest power density available in terms of renewable energy, has the drawback of being erratic. Integrating an energy harvesting and storage device into photovoltaic energy storage modules is a viable route for obtaining self-powered energy systems. Herein, an MXene-based all-solution processed semitransparent flexible photovoltaic supercapacitor (PSC) was fabricated by integrating a flexible organic photovoltaic (OPV) with Ti3C2Tx MXene as the electrode and transparent MXene supercapacitors with an organic ionogel as the electrolyte in the vertical direction, using Ti3C2Tx thin film as a common electrode. In the quest for a semitransparent flexible PSC, Ti3C2Tx MXene was first used as a transparent electrode for OPV with a high power conversion efficiency of 13.6%. The ionogel electrolyte-based transparent MXene supercapacitor shows a high volumetric capacitance of 502 F cm(-3) and excellent stability. Finally, a flexible PSC with a high average transmittance of over 33.5% was successfully constructed by all-solution processing and a remarkable storage efficiency of 88% was achieved. This strategy enables a simple route for fabricating MXene based high-performance all-solution-processed flexible PSCs, which is important for realizing flexible and printable electronics for future technologies.
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3.
  • Zhou, Jie, et al. (författare)
  • Boridene: Two-dimensional Mo4/3B2-x with ordered metal vacancies obtained by chemical exfoliation
  • 2021
  • Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 373:6556, s. 801-
  • Tidskriftsartikel (refereegranskat)abstract
    • Extensive research has been invested in two-dimensional (2D) materials, typically synthesized by exfoliation of van der Waals solids. One exception is MXenes, derived from the etching of constituent layers in transition metal carbides and nitrides. We report the experimental realization of boridene in the form of single-layer 2D molybdenum boride sheets with ordered metal vacancies, Mo4/3B2-xTz (where T-z is fluorine, oxygen, or hydroxide surface terminations), produced by selective etching of aluminum and yttrium or scandium atoms from 3D in-plane chemically ordered (Mo2/3Y1/3)(2)AlB2 and (Mo2/3Sc1/3)(2)AlB2 in aqueous hydrofluoric acid. The discovery of a 2D transition metal boride suggests a wealth of future 2D materials that can be obtained through the chemical exfoliation of laminated compounds.
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4.
  • Dahlqvist, Martin, et al. (författare)
  • Theoretical Prediction and Synthesis of a Family of Atomic Laminate Metal Borides with In-Plane Chemical Ordering
  • 2020
  • Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 142:43, s. 18583-18591
  • Tidskriftsartikel (refereegranskat)abstract
    • All atomically laminated MAB phases (M = transition metal, A = A-group element, and B = boron) exhibit orthorhombic or tetragonal symmetry, with the only exception being hexagonal Ti2InB2. Inspired by the recent discovery of chemically ordered hexagonal carbides, i-MAX phases, we perform an extensive first-principles study to explore chemical ordering upon metal alloying of M2AlB2 (M from groups 3 to 9) in orthorhombic and hexagonal symmetry. Fifteen stable novel phases with in-plane chemical ordering are identified, coined i-MAB, along with 16 disordered stable alloys. The predictions are verified through the powder synthesis of Mo4/3Y2/3 AlB2 and Mo4/3Sc2/3AlB2 of space group R (3) over barm (no. 166), displaying the characteristic in-plane chemical order of Mo and Y/Sc and Kagome ordering of the Al atoms, as evident from X-ray diffraction and electron microscopy. The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential twodimensional derivatives.
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5.
  • Meshkian, Rahele, et al. (författare)
  • Theoretical Analysis, Synthesis, and Characterization of 2D W1.33C (MXene) with Ordered Vacancies
  • 2019
  • Ingår i: ACS APPLIED NANO MATERIALS. - : AMER CHEMICAL SOC. - 2574-0970. ; 2:10, s. 6209-6219
  • Tidskriftsartikel (refereegranskat)abstract
    • Synthesis of delaminated 2D W1.33C (MXene) has been performed by selectively etching Al as well as Sc/Y from the recently discovered nanolaminated i-MAX phases (W2/3Sc1/3)(2)AlC and (W2/3Y1/3)(2)AlC. Both quaternary phases produce MXenes with similar flake morphology and with a skeletal structure due to formation of ordered vacancies. The measured O, OH, and F terminations, however, differ in amount as well as in relative ratios, depending on parent material, evident from X-ray photoelectron spectroscopy. These findings are correlated to theoretical simulations based on first-principles, investigating the W1.33C, and the effect of termination configurations on structure, formation energy, stability, and electronic structure. The theoretical results indicate a favored F-rich surface composition, though with a system going from insulating/semiconducting to metallic for different termination configurations, suggesting a high tuning potential of these materials. Additionally, free-standing W1.33C films of 2-4 mu m thickness and with up to 10 wt % polymer (PEDOT:PSS) were tested as electrodes in supercapacitors, showing capacitances up to 600 F cm(-3) in 1 M H2SO4 and high capacitance retention for at least 10000 cycles at 10 A g(-1). This is highly promising results compared to other W-based materials to date.
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6.
  • Meshkian, Rahele, et al. (författare)
  • W-Based Atomic Laminates and Their 2D Derivative W1.33C MXene with Vacancy Ordering
  • 2018
  • Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 30:21
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural design on the atomic level can provide novel chemistries of hybrid MAX phases and their MXenes. Herein, density functional theory is used to predict phase stability of quaternary i-MAX phases with in-plane chemical order and a general chemistry (W 2/3 M 2 1/3 ) 2 AC, where M 2 = Sc, Y (W), and A = Al, Si, Ga, Ge, In, and Sn. Of over 18 compositions probed, only two—with a monoclinic C2/c structure—are predicted to be stable: (W 2/3 Sc 1/3 ) 2 AlC and (W 2/3 Y 1/3 ) 2 AlC and indeed found to exist. Selectively etching the Al and Sc/Y atoms from these 3D laminates results in W 1.33 C-based MXene sheets with ordered metal divacancies. Using electrochemical experiments, this MXene is shown to be a new, promising catalyst for the hydrogen evolution reaction. The addition of yet one more element, W, to the stable of M elements known to form MAX phases, and the synthesis of a pure W-based MXene establishes that the etching of i-MAX phases is a fruitful path for creating new MXene chemistries that has hitherto been not possible, a fact that perforce increases the potential of tuning MXene properties for myriad applications.
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7.
  • Qin, Leiqiang, 1987-, et al. (författare)
  • Polymer-MXene composite films formed by MXene-facilitated electrochemical polymerization for flexible solid-state microsupercapacitors
  • 2019
  • Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 60, s. 734-742
  • Tidskriftsartikel (refereegranskat)abstract
    • Materials with tailored properties are crucial for high performance electronics applications. Hybrid materials composed of inorganic and organic components can possess unique merits for broad application by synergy between the advantages the respective material type offers. Here we demonstrate a novel electrochemical polymerization (EP) enabled by a 2D transition metal carbide MXene for obtaining conjugated polymer-MXene composite films deposited on conducting substrates without using traditional electrolytes, indispensable compounds for commonly electrochemical polymerization. The universality of the process provides a novel approach for EP allowing fast facile process for obtaining different new polymer/MXene composites with controlled thickness and micro-pattern. Furthermore, high performance microsupercapacitors and asymmetric microsupercapacitors are realized based on the excellent composites benefiting from higher areal capacitance, better rate capabilities and lower contact resistance than conventional electropolymerized polymers. The AMSCs exhibit a maximum areal capacitance of 69.5 mF cm(-2), an ultrahigh volumetric energy density (250.1 mWh cm(-3)) at 1.6 V, and excellent cycling stability up to 10000 cycles. The excellent electrochemical properties of the composite polymerized with MXene suggest a great potential of the method for various energy storage applications.
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8.
  • Tan, Hongwei, et al. (författare)
  • Tactile sensory coding and learning with bio-inspired optoelectronic spiking afferent nerves
  • 2020
  • Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The integration and cooperation of mechanoreceptors, neurons and synapses in somatosensory systems enable humans to efficiently sense and process tactile information. Inspired by biological somatosensory systems, we report an optoelectronic spiking afferent nerve with neural coding, perceptual learning and memorizing capabilities to mimic tactile sensing and processing. Our system senses pressure by MXene-based sensors, converts pressure information to light pulses by coupling light-emitting diodes to analog-to-digital circuits, then integrates light pulses using a synaptic photomemristor. With neural coding, our spiking nerve is capable of not only detecting simultaneous pressure inputs, but also recognizing Morse code, braille, and object movement. Furthermore, with dimensionality-reduced feature extraction and learning, our system can recognize and memorize handwritten alphabets and words, providing a promising approach towards e-skin, neurorobotics and human-machine interaction technologies.
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9.
  • Tao, Quanzheng, 1989- (författare)
  • Synthesis and characterization of two- and three-dimensional nanolaminated carbides
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis is focused towards the synthesis and characterization of novel nanolaminated materials in primarily bulk (powder) form. Of particular interest is magnetic materials, or laminates that can be used as precursor for two-dimensional (2D) materials. 2D materials typically display a large surface-to-volume ratio, and as such they are very promising for applications within energy storage and catalysis. A more recently discovered family of 2D transition metal carbides/nitrides, called MXenes, are currently attracting a lot of attention. MXenes are produced by selective etching of parent 3D nanolaminates, so called MAX phases, facilitating removal of selected atomic layers, and formation of 2D sheets.In my work on new nanolaminates as precursors for 2D materials, I have synthesized (Mo2/3Sc1/3)2AlC and have studied its crystal structure. It was found that Mo and Sc are chemically ordered in the metal layers, with the in-plane ordering motivating the notation i-MAX for this new type of MAX phase alloy. By selective etching of Sc and Al, we thereafter produced a 2D materials with ordered vacancies, Mo1.33C, and studied the electrochemical properties. It was found that the material displayed a high capacitance, ~1200 F cm-3, which is 65% higher that the counterpart without vacancies, Mo2C.I also synthesized a previously not known out-of-plane ordered Mo2ScAlC2 MAX phase. By selective etching of Al, we produced a 2D material, Mo2ScC2, which is correspondingly ordered in the out-of-plane direction. Another related laminated material was also discovered and synthesized, Sc2Al2C3, and its crystal structure was determined. The material is potentially useful for conversion into a 2D material. I have also shown that Sc2Al2C3 is an example of a series of materials with the same crystal structure, with Sc replaced by other metals.Magnetic materials are used in many applications, such as for data storage devices. In particular, layered magnetic materials are of interest due to their anisotropic structure and potential formation of interesting magnetic characteristics. I have been synthesizing and characterizing magnetic nanolaminates, starting with the (V,Mn)3GaC2 MAX phase in the form of an epitaxial thin film. Analysis of the magnetic behavior showed a ferromagnetic response above room temperature I thereafter showed that our previously discovered family of i-MAX phases could be expanded with a subclass of ordered nanolaminates based on rare earth (RE) elements, of the general formula (Mo2/3RE1/3)2AlC , where RE=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. I studied their crystal structure by scanning transmission microscopy (STEM), X-ray diffraction (XRD), and neutron diffraction. We found that these phases can crystalize in three different structures, of space group C2/m, C2/c, and Cmcm, respectively. The magnetic behavior was studied and the magnetic structure of two materials could be determined. We suggest that the complex behavior identified is due to competing magnetic interaction and frustration.I also synthesized another rare earth-based nanolaminate, Mo4Ce4Al7C3. The crystal structure was investigated by single crystal X-ray diffraction and STEM. Magnetization analysis reveal a ferromagnetic ground state below 10.5 K. X-ray absorption near-edge structure provide evidence that Ce is in a mixed-valence state. X-ray magnetic circular dichroism shows that only one of the two Ce sites are magnetic. 
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10.
  • Tao, Quanzheng, et al. (författare)
  • Synthesis, Characterization, and Modeling of a Chemically Ordered Quaternary Boride, Mo4MnSiB2
  • 2023
  • Ingår i: Crystal Growth & Design. - : AMER CHEMICAL SOC. - 1528-7483 .- 1528-7505. ; 23:5, s. 3258-3263
  • Tidskriftsartikel (refereegranskat)abstract
    • The recent discovery of chemical ordering in quaternary borides offers new ways of exploring properties and functionalities of these laminated phases. Here, we have synthesized and investigated chemical ordering of the laminated Mo4MnSiB2 (T2) phase, thereby introducing a magnetic element into the family of materials coined o-MAB phases. By X-ray diffraction and scanning transmission electron microscopy, we provide evidence for out-of-plane chemical ordering of Mo and Mn, with Mo occupying the 16l site and Mn preferentially residing in the 4c site. Mn and B constitute quasi-two-dimensional layers in the laminated material. We have therefore also studied the magnetic properties by magnetometry, and no sign of long-range magnetic order is observed. An initial assessment of the magnetic ordering has been further studied by density functional theory (DFT) calculations, and while we find an antiferromagnetic configuration to be the most stable one, ferromagnetic ordering is very close in energy.
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