Dingsheng Yuan

Large Scale Synthesis of NiCo Layered Double Hydroxides for Superior Asymmetric Electrochemical Capacitor.

We report a new environmentally-friendly synthetic strategy for large-scale preparation of 16 nm-ultrathin NiCo based layered double hydroxides (LDH). The Ni50Co50-LDH electrode exhibited excellent specific capacitance of 1537 F g−1 at 0.5 A g−1 and 1181 F g−1 even at current density as high as 10 A g−1, which 50% cobalt doped enhances the electrical conductivity and porous and ultrathin structure is helpful with electrolyte diffusion to improve the material utilization. An asymmetric ultracapacitor was assembled with the N-doped graphitic ordered mesoporous carbon as negative electrode and the NiCo LDH as positive electrode. The device achieves a high energy density of 33.7 Wh kg−1 (at power density of 551 W kg−1) with a 1.5 V operating voltage.

N-Doped carbon nanorods as ultrasensitive electrochemical sensors for the determination of dopamine

Nitrogen-doped carbon nanorods (N-CNRs) are prepared by a direct carbonization method using polyaniline nanorods as the carbon precursor. The electrochemical behavior of the N-CNRs-Nafion modified electrode is evaluated in connection with dopamine and ascorbic acid by cyclic voltammetry and differential pulse voltammetry. Experimental results indicate that the N-CNRs modified electrode has improved current response and fast electron transfer kinetics. The linear response for the selective determination of dopamine in the presence of ascorbic acid is obtained in the range of 0.008 μM to 15.0 μM with a detection limit of 8.9 × 10−9 M (S/N = 3) by differential pulse voltammetry under optimum conditions. The N-CNRs-Nafion modified electrode exhibits a wide linear range, very low detection limit and anti-interference ability. Meanwhile, a kinetic reaction process and a reaction mechanism for the N-CNRs are also proposed.

Synthesis of graphitic mesoporous carbon from sucrose as a catalyst support for ethanol electro-oxidation

Graphitic mesoporous carbon (GMC) has been prepared with non-toxic and economical sucrose as the carbon precursor and mesoporous iron oxide as a catalyst at a relatively low carbonization temperature. XRD patterns suggest that GMC is formed by a carbide intermediate. The data of nitrogen sorption exhibit that the GMC possesses a mesoporous structure. Pt nanoparticles are uniformly loaded on the graphitic mesoporous carbon by a facile and effective microwave assisted ethylene glycol process. All the results show that the graphitic mesoporous carbon-supported Pt nanoparticles have superior electrocatalytic properties compared to Vulcan XC-72 and CMK-3 catalyst supports, suggesting this novel and general method will have a bright future in fuel cell applications.

A novel route for preparing graphitic ordered mesoporous carbon as electrochemical energy storage material

A graphitic ordered mesoporous carbon (G-OMC) has been synthesized for the first time using mesoporous nickel oxide as a template and catalyst and dopamine as a carbon source. The probable formation mechanism for the preparation of G-OMC is also proposed. Characterization by X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy indicate that the as-prepared mesoporous carbon has a high degree of graphitization. The electrochemical performance of G-OMC is visibly superior to typical CMK-3D in alkalic media, involving fast kinetic transfer, anti-corrosion, a capacitance of 68 μF cm−2 at 0.1 A g−1 and a light increase of the 6000th-cycle capacitance compared to the initial capacitance. In organic electrolyte, a wider potential window of 2.5 V is presented. The fast charge transfer, quick response and anti-corrosion properties promise that G-OMC will have a great prospect as a supercapacitor for energy storage applications.

Simple Shape-Controlled Synthesis of Carbon Hollow Structures

This study reports a simple method for the controlled synthesis of uniformly shaped carbon hollow structures by an ethanol-assisted thermolysis of zinc acetate. The experimental evidence reveals that the generated zinc oxide nanostructures act as in-situ templates to form the carbon hollow structures. The morphologies, including the shell thickness, cavity size, and aspect ratio, can be controlled by the reaction time and the heating procedure, and hollow nanospheres, nanocapsules, nanorods, and microtubes can be obtained. Experimental results show that the as-synthesized carbon hollow structures exhibit excellent thermal and structural stability to temperatures as high as 1200 °C.

Preparation and properties of antibacterial TiO2@C/Ag core?shell composite

Abstract An environment-friendly hydrothermal method was used to prepare TiO2@C core–shell composite using TiO2 as core and sucrose as carbon source. TiO2@C served as a support for the immobilization of Ag by impregnation in silver nitrate aqueous solution. The chemical structures and morphologies of TiO2@C and TiO2@C/Ag composite were characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy and Brunauer–Emmett–Teller (BET) analysis. The antibacterial properties of the TiO2@C/Ag core–shell composite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the viable cell counting method. The results indicate that silver supported on the surface of TiO2@C shows excellent antibacterial activity.

Metal-free N-doped carbon nanofibers as an efficient catalyst for oxygen reduction reactions in alkaline and acid media

The development of metal-free catalysts to replace the use of Pt has played an important role in relation to its application to fuel cells. We report N-doped carbon nanofibers as the catalyst of an oxygen reduction reaction, which were synthesized via carbonizing bacterial cellulose-polypyrrole composites. The as-prepared material exhibited remarkable catalytic activity toward the oxygen reduction reaction with comparable onset potential and the ability to limit the current density of commercial Pt/C catalysts in both alkaline and acid media due to the unique porous three-dimensional network structure and the doped nitrogen atoms. The effect of N functionalities on catalytic behavior was systematically investigated. The results demonstrated that pyridinic-N was the dominating factor for catalytic performance toward the oxygen reduction reaction. Additionally, N-doped carbon nanofibers also demonstrated excellent cycling stability (93.2% and 89.4% retention of current density after chronoamperometry 20 000 s in alkaline and media, respectively), obviously superior to Pt/C.

Fe/N co-doped carbon microspheres as a high performance electrocatalyst for the oxygen reduction reaction

Recently, nitrogen-doped carbon materials have attracted immense interest because of their great potential in various applications. In this work, FeN-doped carbon microspheres are large-scale synthesized using basic magnesium carbonate as the template and glycine as the carbon and nitrogen precursor by a simple liquid impregnation method under a relatively low pyrolysis temperature. Iron is introduced into the carbon microspheres to enhance the graphitic degree and improve the electrocatalytic performance. This carbon material with high specific area, high nitrogen content and part-graphitization shows high activity and four-electron selectivity for the oxygen reduction reaction in an alkaline medium. Compared to a commercial Pt/C catalyst, this material presents exceeding stability and durability, which can be a candidate for potential applications in the fuel cell and electrochemical industries of oxygen reduction.

Synthesis of ZnO@CNTs From Anhydrous Zinc Acetate via Thermal Decomposition

The ZnO@CNTs has been prepared via a thermal decomposition route. The spectra of X-ray powder diffraction (XRD) prove that as-prepared ZnO is primitive hexagonal phase and CNTs with an interlayer distance of 0.34 nm is low graphitized carbon in this research. The diameter and length of ZnO@CNTs are 150–200nm and 1.5–2µm, respectively. The vibration on 1625cm –1 , 1540cm –1 and 1380 cm –1 shows that the surface of ZnO@CNTs have great functional groups. Advance materials prepared via thermal decomposition techniques attract broad research interests [1-3]. In appropriate temperature and pressure, the size and structure of materials are controlled through the synthesis condition. Cha and co-workers have revealed that the thermal decomposition is economical and easy method to synthesis some monodispersed nanocrystal [3]. Metal oxide and carbon materials have been widely fabricated via thermal decomposition [2-9]. Carbon nanotubes (CNTs) with unique physical and chemical properties have broad applications in the field of many high-tech, especially assembled other nano-materials on the surface of CNTs to achieve the function of the CNTs. At the same time, ZnO has received widespread attention for its excellent performance in electronics, optics, photonics systems. So many scientists have considerable paid attention to assemble ZnO to carbon nanotubes to obtain excellent optics, catalyse, anti-bacterial properties. The ZnO@CNTs materials have been fabricated using many methods, such as electrostatic coordination approach [10], plasmaassisted sputtering technique [11], chemical vapor deposition[12,13] and so on. However, to the best of our knowledge, there is no report on the preparation of carbon nanotubes coating ZnO composite. In this study, the ZnO@CNTs has been prepared via thermal decomposition anhydrous zinc acetate without any catalyst and toxic reagents. The surface functional groups of CNTs have been investigated.

Synthesis of 3D-MoO2 microsphere supported MoSe2 as an efficient electrocatalyst for hydrogen evolution reaction

Many efforts have been devoted to the exploration of non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) in recent years. Here, we have developed a 3D-MoO2 microsphere supported MoSe2 for HER, via a facile hydrothermal approach followed by selenylation treatment. Loosely stacked MoSe2 layers are formed on the conductive MoO2 surface, and act as active sites for HER. Meanwhile, the metallic inner MoO2 facilitates electron transport for proton reduction. In addition, the MoSe2 could protect the inner MoO2 from the acidic electrolyte in the HER precess. Significantly, the as-synthesized MoO2/MoSe2 exhibits excellent catalytic activity for HER, characterised by a low onset potential of -101 mV vs reversible hydrogen electrode, a small overpotential of 167 mV at a current density of 10 mA cm-2, along with Tafel slope values of 68 mV dec-1, as well as outstanding stability in 0.5 mol L-1 H2SO4.Many efforts have been devoted to explore non-noble metal electrocatalysts for hydrogen evolution reaction (HER) in recent years. Here, we developed a 3D-MoO2 microspheres supported MoSe2 via a facile hydrothermal approach followed by selenylation treatment for HER. The loosely stacked MoSe2 layer were formed on the conductive MoO2 surface and acted as active sites for HER. Meanwhile, metallic inner MoO2 facilitates to electron transport for proton reduction. In addition, the MoSe2 could protect the inner MoO2 from the acidic electrolyte in the HER precess. Significantly, the as-synthesized MoO2/MoSe2 exhibits excellent catalytic activity for HER featured by a low onset potential of -101 mV vs reversible hydrogen electrode, a small overpotential of 167 mV at a current density of 10 mA cm-2 along with Tafel slope values of 68 mV dec-1 as well as outstanding stability in 0.5 mol L-1 H2SO4.