Xingwei Li

High-Performance Asymmetric Supercapacitor Based on Nanoarchitectured Polyaniline/Graphene/Carbon Nanotube and Activated Graphene Electrodes

Hierarchical sulfonated graphene nanosheet/carboxylated multiwalled carbon nanotube/polyaniline (sGNS/cMWCNT/PANI) nanocomposites were synthesized through an interfacial polymerization method. Activated porous graphene (aGNS) was prepared by combining chemical foaming, thermal reduction, and KOH activation. Furthermore, we have successfully fabricated an asymmetric supercapacitor (ASC) using sGNS/cMWCNT/PANI and aGNS as the positive and negative electrodes, respectively. Because of its unique structure, high capacitive performance, and complementary potential window, the ASC device can be cycled reversibly at a cell voltage of 1.6 V in a 1 M H2SO4 aqueous electrolyte, delivering a high energy density of 20.5 Wh kg(-1) at a power density of 25 kW kg(-1). Moreover, the ASC device also exhibits a superior long cycle life with 91% retention of the initial specific capacitance after 5000 cycles.

Carbon nanotubes/tin oxide nanocomposite-supported Pt catalysts for methanol electro-oxidation

Carbon nanotubes/tin oxide nanocomposite (MWCNTs-SnO2) was obtained via the hydrolysis of SnCl4 in the presence of multi-walled carbon nanotubes (MWCNTs) and subsequent calcinations. And carbon nanotubes/tin oxide nanocomposite-supported Pt catalysts (Pt/MWCNTs-SnO2) were prepared by in-situ liquid phase reduction using H2PtCl6 as a metal precursor. As-prepared catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), and their catalytic performances were evaluated by chronoamperometry (CA) and cyclic voltammetry (CV). Desirable catalytic performance for methanol electro-oxidation was observed with a reduced size and an improved dispersion of Pt catalysts on the MWCNTs-SnO2 nanocomposite. The calcination temperature of MWCNTs-SnO2 nanocomposite was a key factor for controlling the catalytic performance of Pt/MWCNTs-SnO2 catalysts.

Different polyaniline/carbon nanotube composites as Pt catalyst supports for methanol electro-oxidation

Polyaniline/carbon nanotube composites as Pt catalyst supports for methanol electro-oxidation have been reported. Conventionally, the size and distribution of Pt catalysts were improved in the presence of polyaniline (PAni), and an interaction between Pt and N atoms in PAni could prevent Pt catalysts from aggregation and detachment. In this work, polyaniline-modified multi-walled carbon nanotube (PAni-MWCNT) composites, with different loading levels of PAni, were synthesized by in situ oxidative polymerization of aniline on the surface of MWCNT. And Pt catalysts supported by these composites were prepared by the liquid phase reduction. Our studies revealed that the loading level of PAni affected the proportion of the different valence Pt components. And the proportion of Pt(0) and Pt(II) was also important for improving the electro-catalytic performance of Pt catalysts. The proper proportion of Pt(II) was essential for coordination of Pt with oxygen-containing ligands (OH·, H2O) and thus accelerating oxidation of Pt (CO)ads with release of CO2 by improving the tolerance to intermediate carbonaceous species.

Synthesis of new polyether titanate coupling agents with different polyethyleneglycol segment lengths and their compatibilization in calcium sulfate whisker/poly(vinyl chloride) composites

Six new polyether titanate coupling agents with different polyethyleneglycol (PEG) segment lengths were prepared in this study and were then used to modify calcium sulfate whiskers (CSWs) in order to improve the compatibility between CSWs and poly(vinyl chloride) (PVC). The chemical structure of these coupling agents was characterized by FTIR, Raman, 1H NMR and 31P NMR, and the surface properties of CSWs modified by the coupling agents (mCSWs) were characterized by FTIR, SEM-EDS and XPS. Then, CSW/PVC and mCSW/PVC composites were prepared using a two-roll mill, and their mechanical and thermal properties were characterized to investigate the effects of the PEG segment length of the coupling agents on the performance and compatibility of the composites. The results show that the new coupling agents can significantly improve the compatibility and the interfacial adhesion between CSWs and the PVC matrix, which results in a significant improvement of the comprehensive performance of mCSW/PVC composites. PEG4000 shows the best modification effect on CSWs. Finally, the underlying mechanisms are discussed.

Synthesis and electrochemical capacitance performance of polyaniline doped with lignosulfonate

Polyaniline doped with lignosulfonate (PANI/LGS) was prepared by using a facile oxidative polymerization of aniline with (NH4)2S2O8 as an oxidant, and the structure and morphology of PANI/LGS were investigated. As an active material for supercapacitors, the capacity retention rate of PANI/LGS was 75.1% with a growth of current density from 0.2 to 10 A g−1, indicating a high rate performance, and that of PANI was only 38.3%. For PANI/LGS, a specific capacitance of 377.2 F g−1 remained at 10 A g−1, and that of PANI was 183.7 F g−1. Moreover, the cycling stability was also measured in a two-electrode symmetrical capacitor at a current density of 1.0 A g−1. The capacity retention rate of PANI/LGS was 74.3% after 10 000 cycles, and that of PANI was 52.8%.

Effect of inorganic–organic surface modification of calcium sulfate whiskers on mechanical and thermal properties of calcium sulfate whisker/poly(vinyl chloride) composites

Coupling agents are traditionally used to improve the interfacial adhesion between inorganic fillers and a polymer matrix; however, the application of this method is somewhat limited by the number of hydroxyl groups on the surface of inorganic fillers. In this study, a layer of calcium hydroxide (Ca(OH)2) was coated on the surfaces of calcium sulfate whiskers (CSW) through hydroxylation modification using sodium hydroxide (NaOH) to increase the hydroxyl groups of the CSW, and then a polyether titanate coupling agent synthesized in our lab was used to modify Ca(OH)2 coated CSW in order to improve their compatibility with poly(vinyl chloride) (PVC). The chemical structure and surface properties of the modified CSW were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA). Then, CSW/PVC and modified CSW/PVC composites were prepared via a two-roll mill, and the effects of the inorganic–organic surface modification of CSW on their mechanical and thermal properties were evaluated. The results show that hydroxylation modification can further improve the compatibility and the interfacial adhesion between CSW and the PVC matrix, which results in better mechanical and thermal properties.

Surface modification of polyaniline using tetraethyl orthosilicate

A well-dispersible conducting polyaniline/silica hybrid is prepared by the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) on the surface of polyaniline in water/ethanol solution. It provides a simple and environmentally sound route for preparing the processable conducting polyaniline/silica hybrid at the nanometre level. The conductivity of polyaniline/silica hybrid is 2.43 S cm(-1) at 25 degrees C, and its powder is easily dispersed in the anhydrous ethanol or aqueous solution without any stabilizer. In addition, the structure, morphology and cyclic voltammorgram of this hybrid are also reported.

High-performance stretchable supercapacitors based on intrinsically stretchable acrylate rubber/MWCNTs@conductive polymer composite electrodes

The key to fabricating high-performance stretchable supercapacitors (SSCs) is the design of intrinsically stretchable electrodes. However, there are few reports focusing on this, especially in organic electrolytes with a broader potential window. In this work, we have fabricated novel intrinsically stretchable electrodes made of acrylate rubber/multiwall carbon nanotube (ACM/MWCNT) composite film supported poly(1,5-diaminoanthraquinone) or polyaniline (ACM/MWCNTs@PDAA and ACM/MWCNTs@PANI). The ACM/MWCNT film with 35 wt% MWCNTs shows a high conductivity (9.6 S cm−1), high stretchability (155%) and good elastic resilience (11.7% plastic deformation after 500 stretching cycles at 50% strain). The ACM/MWCNTs@PDAA anode and ACM/MWCNTs@PANI cathode exhibit a high volumetric specific capacitance of 20.2 and 17.2 F cm−3 at 1 mA cm−2, respectively. To demonstrate the good performance of the as-prepared stretchable electrodes, an organic asymmetric stretchable supercapacitor (oASSC) is assembled conveniently by using ACM/MWCNTs@PANI as the cathode, ACM/MWCNTs@PDAA as the anode, and ACM/Et4NBF4–AN as the quasi-solid-state polymer electrolyte (QPE). The oASSC delivers an outstanding energy density of 2.14 mW h cm−3 and good cycling stability under static and 50% strain conditions, which makes it superior to most reported stretchable supercapacitors.