Yuying Zheng

Three-dimensional and stable polyaniline-grafted graphene hybrid materials for supercapacitor electrodes

A novel route is introduced to synthesize hierarchical polyaniline-grafted reduced graphene oxide (rGO) hybrid materials by polyaniline nanorods covalently bonded on the surface of rGO. Aminophenyl groups were initially grafted on rGO via diazonium treatment. Then the PANI nanorods were aligned vertically on rGO to construct a three-dimensional (3D) structure. The 3D structure could shorten the electronic transmission path and form abundant space for electrolyte ions. The hybrid materials fabricated as supercapacitor electrodes exhibited a maximal specific capacitance of 1045.51 F g−1, and the energy density (E) could achieve an upper value of 8.3 W h kg−1 at the current density of 0.2 A g−1 simultaneously. Such highly stable three-dimensional structural materials are very promising for the next generation of high-performance electrochemical supercapacitors.

Controllable Preparation of Polyaniline–Graphene Nanocomposites using Functionalized Graphene for Supercapacitor Electrodes

In order to explore the effect of graphene surface chemistry on electrochemical performance based on polyaniline-graphene hybrid material electrodes, four different polyaniline-graphene nanocomposites were fabricated with graphene oxide, reduced graphene oxide, aminated graphene and sulfonated graphene as carriers, respectively. The nanocomposites feature various structures and morphologies, which could be used to more deeply understand the morphology and structure effects caused by surface chemistry on electrochemical performance. The experimental results reveal that functionalized electronegative graphene was conducive to the vertical and neat growth of polyaniline (PANI) nanorods. The array architecture endowed the PANI-GS nanocomposite with a large ion-accessible surface area and high-efficiency electron- and ion-transport pathways. Meanwhile, the introduction of sulfonic acid functional groups accelerated the redox reaction with doping and dedoping of the PANI. Thereby, the PANI-GS nanocomposite exhibited a high specific capacitance of 863.2 F g(-1) at a current density of 0.2 A g(-1) and the excellent rate capability of 67.4 % (581.6 F g(-1) at 5 A g(-1) ), which were much better than the other three nanocomposites produced.

Low-temperature NO reduction with NH3 over Mn–CeOx/CNT catalysts prepared by a liquid-phase method

Herein, we report a simple and effective way to prepare Mn–Ce mixed-oxide catalysts supported on carbon nanotubes for low-temperature selective catalytic reduction of NO with NH3. The catalysts with amorphous structures all showed nearly 100% NO conversion at 120–180 °C with a space velocity of 30000 h−1.

Layer-by-Layer Self-Assembled Graphene Multilayer Films via Covalent Bonds for Supercapacitor Electrodes

To maximize the utilization of its single-atom thin nature, a facile scheme to fabricate graphene multilayer films via a layer-by-layer self-assembled process was presented. The structure of multilayer films was constructed by covalently bonding graphene oxide (GO) using p-phenylenediamine (PPD) as a covalent cross-linking agent. The assembly process was confirmed to be repeatable and the structure was stable. With the π-π conjugated structure and a large number of spaces in the framework, the graphene multilayer films exhibited excellent electrochemical performance. The uniform ultrathin electrode exhibited a capacitance of 41.71 μF/cm2 at a discharge current of 0.1 μA/cm2, and displayed excellent stability of 88.9 % after 1000 charge-discharge cycles.

Metal lanolin fatty acid as novel thermal stabilizers for rigid poly(vinyl chloride)

Abstract The synergistic stabilization effect of different metal lanolin fatty acids as natural-based thermal stabilizers for poly(vinyl chloride) (PVC) including calcium lanolin fatty acid (Calan2), zinc lanolin fatty acid (Znlan2) and lanthanum lanolin fatty acid (Lalan3) were studied through Congo red testing, color measurements, FTIR analyses and thermal behavior in this paper. The results showed that Lalan3/Calan2/Znlan2 stabilizers exhibited more excellent thermal stabilization efficiency to PVC than Calan2/Znlan2 thermal stabilizers, and the optimal mass ratio of Lalan3/Calan2/Znlan2 was 8:9:3. At last, the effect of degradation mechanism on PVC and synergistic stabilization was also investigated by FTIR analyses and thermal behavior.

Fabrication of Mn-FeOx/CNTs Catalysts for Low-Temperature NO Reduction with NH3

Mn-FeOx/carbon nanotubes (CNTs) catalysts were firstly prepared via simple incipient wetness method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. The structure and surface properties of the catalysts were characterized by N2 sorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H2-TPR). It was found that Mn-FeOx/CNTs catalyst exhibited excellent low-temperature SCR activity and SO2 resistance. XRD patterns revealed that metal oxides catalysts were possessed of amorphous structure. FESEM and TEM images showed that metal oxides catalysts were successfully supported on CNTs. The XPS results indicated that the obtained catalyst presented high Mn4+/Mn3+ and OS/(OS + OL) ratios. The H2-TPR profiles showed that Mn-FeOx/CNTs catalyst possessed better low-temperature reducibility. Besides, the obtained catalyst exhibited better SO2 resistance.

Fabrication of Mn–CeOx/CNTs catalysts by a redox method and their performance in low-temperature NO reduction with NH3

Highly active Mn–CeOx/CNTs catalysts were first fabricated by a novel redox method, and a formation mechanism was proposed. The as-obtained catalyst possessed an amorphous structure, and high Ce3+/(Ce3+ + Ce4+) and Oα/(Oα + Oβ) ratios, which endowed it with 52.2–98.4% NO conversion at a weight hourly space velocity of 210 000 ml gcat−1 h−1.

MnO2 catalysts uniformly decorated on polyphenylene sulfide filter felt by a polypyrrole-assisted method for use in the selective catalytic reduction of NO with NH3

A manganese dioxide (MnO2)/polypyrrole (PPy) nanocoating was uniformly decorated on the surface of polyphenylene sulfide (PPS) filter felt via an in situ synthesis method to fabricate a catalytic filter material. The pyrrole functioned as a dispersant for the MnO2 catalysts and the PPy generated acted as a binder to adhere the MnO2 catalysts and filter felt together. The catalytic filter material obtained, had a high adhesive strength between that of the MnO2/PPy nanocoating and the PPS filter felt, and was used for the selective catalytic reduction of nitric oxide (NO) with ammonia under model conditions without any sulfur dioxide or water vapor in the gas. More than 70% conversion of NO was achieved at 160–180 °C at a high space velocity of 38 000 h−1.

Nitrogen doped graphite felt decorated with porous Ni1.4Co1.6S4 nanosheets for 3D pseudocapacitor electrodes

3D electrodes are of significant importance for the development of wearable electronics. In this manuscript, nitrogen doped graphite felt (NGF) and Ni1.4Co1.6S4 have been selected as a 3D conducting matrix and redox-active species for pseudocapacitor electrodes, respectively. The hydrothermal growth of Ni1.4Co1.6S4 in the presence of NGF yields stand-alone and bendable composite electrodes where Ni1.4Co1.6S4 forms porous nanosheets dispersed uniformly along the NGF surface. The experimental results show that the Ni1.4Co1.6S4/NGF electrode achieves a remarkable specific capacitance of 1625 F g−1 at a current density of 1 A g−1, which is maintained at 1465 F g−1 when the current density is increased to 20 A g−1. After cycling at a current density of 20 A g−1 for 2000 cycles, the Ni1.4Co1.6S4/NGF electrode still delivers 90.2% of its original specific capacitance. Such encouraging rate capability and cycling stability of the Ni1.4Co1.6S4/NGF electrode are attributed to the desirable Ni1.4Co1.6S4 nanostructure and the synergistic effect of the good electron conductivity and excellent surface property of the NGF substrate. The outstanding electrochemical performance of the Ni1.4Co1.6S4/NGF electrode makes it a promising candidate for 3D pseudocapacitor applications.

Effect of annealing on tensile properties of electrodeposited nanocrystalline Ni with broad grain size distribution

Abstract The microstructures and tensile properties of electrodeposited nanocrystalline Ni (nc-Ni) with a broad grain size distribution after annealing at 150, 200 and 300°C for 500 s were investigated. The as deposited broad grain size distribution nc-Ni sample exhibited a moderate strength σUTS of ∼1107 MPa but a markedly enhanced ductility ϵTEF of ∼10%, compared with electrodeposited nc-Ni with a narrow grain size distribution. Annealing below 200°C increased the strength but caused a considerably reduction in tensile elongation. This behaviour is attributed to the grain boundary relaxation and the increased order of grain boundaries after annealing, which can make the grain boundary activities, such as the grain boundary sliding and grain rotations, more difficult. Further annealing at 300°C decreased both the yield strength and tensile elongation significantly due to significant grain growth.