Changsheng Liu

Flexible pillared graphene-paper electrodes for high-performance electrochemical supercapacitors.

Flexible graphene paper (GP) pillared by carbon black (CB) nanoparticles using a simple vacuum filtration method is developed as a high-performance electrode material for supercapacitors. Through the introduction of CB nanoparticles as spacers, the self-restacking of graphene sheets during the filtration process is mitigated to a great extent. The pillared GP-based supercapacitors exhibit excellent electrochemical performances and cyclic stabilities compared with GP without the addition of CB nanoparticles. At a scan rate of 10 mV s(-1) , the specific capacitance of the pillared GP is 138 F g(-1) and 83.2 F g(-1) with negligible 3.85% and 4.35% capacitance degradation after 2000 cycles in aqueous and organic electrolytes, respectively. At an extremely fast scan rate of 500 mV s (-1) , the specific capacitance can reach 80 F g(-1) in aqueous electrolyte. No binder is needed for assembling the supercapacitor cells and the pillared GP itself may serve as a current collector due to its intrinsic high electrical conductivity. The pillared GP has great potential in the development of promising flexible and ultralight-weight supercapacitors for electrochemical energy storage.

Tailoring oxidation degrees of graphene oxide by simple chemical reactions

High quality graphene oxide (GO) with controllable degrees of oxidation was synthesized by simple chemical reactions inspired by approaches to unzip single wall carbon nanotubes using strong oxidizing agents. As compared to the conventional Hummers method, these reactions are less exo-therm involved without emission of toxic gases. The structural characteristics of the synthesized GO with various oxidation degrees were evaluated by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, thermal gravimetric analysis, and UV-vis-IR spectroscopy. GO with tailored degrees of oxidation displays tunable optoelectronic properties and may have a significant impact on developing graphene- or GO-based platforms for various technological applications.

Electrospray deposition of a Co3O4 nanoparticles–graphene composite for a binder-free lithium ion battery electrode

A binder-free anode was fabricated from a Co3O4–graphene composite by direct electrospray deposition on current collectors. The highly-interconnected mesoporous structure enables fast ion transport and accommodates the volume expansion of Co3O4 upon Li+ insertion/extraction. The incorporation of highly conductive graphene also improves the charge transport and thus the electrochemical performance.

Scaling of reliability of gold interconnect lines subjected to alternating current

We present an investigation of damage morphologies of small-scale gold interconnect lines subjected to thermal fatigue strain generated by alternating current. Fractal dimension analysis reveals a general scaling relation between the critical strain range causing thermal fatigue damage and the ratio of the width to the thickness of the metal line. Such the scaling rule may be useful in controlling reliability of the metal interconnect lines subjected to long-term thermal cyclic strain

Superhydrophobic surfaces on brass substrates fabricated via micro-etching and a growth process

Constructing artificial superhydrophobic surfaces is an effective strategy for improving the properties of traditional materials. In this paper, we report an easy method for preparing superhydrophobic surfaces on brass to expand its field of application. The micro–nanostructure on the brass surface was constructed via micro-etching technology, and the resulting surface energy was reduced via stearic acid modification. The surface was analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. The brass surface was converted from hydrophilic to superhydrophilic to superhydrophobic. Bending and abrasion tests were used to characterize the mechanical durability of the surface. Additionally, the obtained surface exhibited a superior self-cleaning performance. We propose that this method has a promising future for superhydrophobic surface fabrication and can expand the applications of brass.

GRAPHENE AND GRAPHENE-BASED NANOCOMPOSITES: SYNTHESIS AND SUPERCAPACITOR APPLICATIONS

Graphene, a single-atomic-thick sheet, consists of sp-bonded carbon atoms in hexagonal lattice and possesses excellent physical and chemical properties such as high surface area, conductivity, mechanical strength and lightweight. The two-dimensional geometry of graphene nanosheets is ideal for many applications especially in electrochemical energy storage. However, the large-scale production of graphene materials is still a bottleneck limiting the development of advanced energy storage devices. The production of graphene oxide is one of the most critical restrictions in term of synthesis of graphene by wet chemical methods. We have demonstrated the synthesis of high quality graphene oxide by simple chemical reactions with less exo-therm involved without emission of toxic gases, which is more favorable than conventional methods for commercialized synthesis of graphene materials (Figure 1.). Meanwhile, pseudo-capacitive materials such as Co3O4 and MnSn(OH)6 coupled with graphene nanosheets were synthesized by soft chemical methods in order to utilize both advantages from electrical double layer and pseudo-mechanisms. Their electrochemical properties were evaluated and the potential applications used as high performance electrodes for capacitive energy storage were discussed as well.