Control of oxidation state of copper in flame deposited films

The deposition of thin copper based films onto carbon steel surface is described, using premixed flames with different oxygen/methane ratios doped with aqueous copper nitrate as precursor. We investigated the chemical properties of the copper as a function of oxygen/methane ratio. Using fuel rich flames (equivalence ratio 0.665), the deposited copper film was entirely metallic. When the equivalence ratio was increased to 0.850 or greater the copper film contained predominantly Cu2 +. Furthermore, the flame can be used for post deposition modification, as demonstrated by reduction of Cu2 + containing films to Cu metal. All the films were characterised by X-ray diffraction, Raman and scanning electron microscopy (SEM). A rotating sample holder was employed to avoid over heating of the sample and the critical variables such as sample height in the flame and deposition time were optimised. Deposition for 20 min, which translated to a total residence time in the flame of approx. 76 s, produces metallic copper films of thickness 169 ± 18 nm as determined by anodic stripping and SEM. The microstructure of the metallic films was clearly composed of fused copper spheres of 100–150 nm, which are probably formed in the flame and subsequently deposited on the surface with good adhesion

Plasma electrochemistry: development of a reference electrode material for high temperature plasma.

This report describes the development of a high temperature reference electrode material for gas phase electrochemistry investigations. The electrode is constructed by careful assessment of different metal/metal oxide materials and operational stability in flame electrolyte medium. This will enable reliable dynamic electrochemistry investigations into redox reactions at the solid/gas interface, free of any solvent defined potential window restrictions

Ball-milled Si powder for the production of H2 from water for fuel cell applications

The development of a safe technique for the supply of hydrogen to small portable fuel cells has emerged as a significant barrier to their deployment in recent years, with solutions centering on the use of hydrogen absorption materials, or the generation of hydrogen through chemical reaction. In the present work we demonstrate that the ball-milling of Si under inert conditions in the presence of KOH and sucrose results in the formation of a fine Si-based powder which reacts spontaneously with water at ambient starting temperature to evolve hydrogen rapidly at high yield. Embedded KOH is capable of accelerating the hydrolysis reaction of silicon by the self-heating effect attributed to dissolution heat of KOH, obviating the need for external heating to initiate the reaction; it also reduces the sensitivity of the reaction to oxide contamination of the Si surface by enabling its dissolution in the form of soluble silicates. Moreover, the silicon-water reaction can be switched on and off by adjusting the ambient temperature. It is shown that ball-milled, KOH-embedded Si powder is able to react with different water sources, such as tap water, river water, and salt water, to produce H2 under aerobic conditions. The method represents a cheap scalable approach for the safe provision of hydrogen fuel to small fuel cells

High-performance supercapacitors of carboxylate-modified hollow carbon nanospheres coated on flexible carbon fibre paper: Effects of oxygen-containing group contents, electrolytes and operating temperature

Although carbon black nanoparticles (CBs) at ca. 10 wt.% are widely used as a conductive additives for energy storage electrodes for lithium ion batteries and supercapacitors, they are not extensively used as the active materials for such devices due to their poor ionic conductivity and wettability. In this work, CBs were oxidized by a process of refluxing with conc. HNO3 for 6-72 h, providing oxidized CBs (OCBs) with different oxygen-containing groups (i.e., carboxyl, hydroxyl, and carbonyl) and contents. The OCBs refluxed for 12 h have ca. 2.0-fold higher accessible active surface area than that of the pristine CBs. The as-fabricated symmetric supercapacitor using OCBs refluxed for 12 h with a [BMP][DCA] ionic liquid electrolyte exhibits specific energy and maximum specific power of 88 Wh kg-1 and 8429 W kg-1, respectively with the capacitance retention over 97% after 6000 cycles. A single coin-cell supercapacitor prototype fully charged can supply electrical power to a red LED over 24 min. This device may be practically used as a battery replacement in high power applications

New routes to functionalize carbon black for polypropylene nanocomposites

Methods for chemical surface functionalization for carbon black (CB) nanoparticles were studied to produce (CB)/polypropylene (PP) nanocomposites with superior electrical and thermal properties. Nanoparticle dispersion is known to directly control the extent to which nanocomposites maximize the unique attributes of their nanoscale fillers. As a result, tailored nanoparticle surface chemistry is a widely utilized method to enhance the interfacial interactions between nanoparticles and polymer matrices, assisting improved filler dispersion. In this work, a rapid chemical functionalization approach using a number of diarylcarbene derivatives, followed by the azo-coupling of substituted diazonium salts, for the covalent introduction of selected functional groups to the CB surface, is reported. Characterization of the modified CB by XPS, TGA, CHN, and ATR-IR collectively confirmed surface functionalization, estimating surface grafting densities of the order of 10(13) and 10(14) molecules/cm(2). Nanocomposites, synthesized by solvent mixing PP with pristine and modified CB, demonstrated macroscopic property changes as a result of the nanoparticle surface functionalization. Pronounced improvements were observed for PP nanocomposites prepared with a dodecyl-terminated diaryl functionalized CB, in which TEM analysis established improved nanofiller dispersion owing to the enhanced CB-PP interfacial interactions in the nanocomposite. Observed dielectric relaxation responses at 20 wt % loading and a reduced percolation threshold realized conductivities of 1.19 × 10(-4) S cm(-1) at 10 wt %, compared to 2.62 × 10(-15) S cm(-1) for pristine CB/PP nanocomposites at the same filler loading. In addition, thermal properties signify an increase in the number of nucleation sites by the raised degree of crystallinity as well as increased melting and crystallization temperatures

High-performance supercapacitors of carboxylate-modified hollow carbon nanospheres coated on flexible carbon fibre paper: Effects of oxygen-containing group contents, electrolytes and operating temperature

Although carbon black nanoparticles (CBs) at ca. 10 wt.% are widely used as a conductive additives for energy storage electrodes for lithium ion batteries and supercapacitors, they are not extensively used as the active materials for such devices due to their poor ionic conductivity and wettability. In this work, CBs were oxidized by a process of refluxing with conc. HNO3 for 6-72 h, providing oxidized CBs (OCBs) with different oxygen-containing groups (i.e., carboxyl, hydroxyl, and carbonyl) and contents. The OCBs refluxed for 12 h have ca. 2.0-fold higher accessible active surface area than that of the pristine CBs. The as-fabricated symmetric supercapacitor using OCBs refluxed for 12 h with a [BMP][DCA] ionic liquid electrolyte exhibits specific energy and maximum specific power of 88 Wh kg-1 and 8429 W kg-1, respectively with the capacitance retention over 97% after 6000 cycles. A single coin-cell supercapacitor prototype fully charged can supply electrical power to a red LED over 24 min. This device may be practically used as a battery replacement in high power applications

Nanostructured Boron Doped Diamond Electrodes with Increased Reactivity for Solar Driven CO2 Reduction in Room Temperature Ionic Liquids

Conductive, boron doped diamond BDD is an extraordinary material with many applications in electrochemistry due to its wide potential window, outstanding robustness, low capacitance and resistance to fouling. However, in photoelectrochemistry, BDD usually requires UV light for excitation, which impedes e. amp; 8201;g., usage in CO2 to fuel reduction. In this work, a heavily boron doped, nanostructured diamond electrode with enhanced light absorption has been developed. It is manufactured from BDD by reactive ion etching and presents a coral amp; 8208;like structure with pore diameters in the nanometer range, ensuring a huge surface area. The strong light absorbance of this material is clearly visible from its black color. Consequently, the material is called Diamond Black DB . Electrochemical and X amp; 8208;ray photoelectron spectroscopy measurements performed at near amp; 8208;ambient pressure conditions of water vapor demonstrate increased surface reactivity for the hydrogen amp; 8208;terminated DB compared to oxidized surfaces. Depending on the surface termination, the wettability and hence the electrochemically accessible area can be changed. Photoelectrochemical conversion of CO2 was demonstrated using a Cu2O amp; 8208;modified electrode in ionic liquids under solar illumination. High formic acid production rates at low catalyst deposition times can be obtained paired with an increased catalyst stability on the DB surfac

Microplasma : a new generation of technology for functional nanomaterial synthesis

Plasma technology has been widely applied in the ozone production, material modification, gas/water cleaning, etc. Various nanomaterials were produced by thermal plasma technology. However, the high temperature process and low uniformity products limit their application for the high value added chemicals synthesis, for example the functional materials or the temperature sensitive materials. Microplasma has attracted significant attentions from various fields owing to its unique characteristics, like the high-pressure operation, non-equilibrium chemistry, continuous-flow, microscale geometry and self-organization phenomenon. Its application on the functional nanomaterial synthesis was elaborately discussed in this review paper. Firstly, the main physical parameters were reviewed, which include the electron temperature, electron energy distribution function, electron density and the gas temperature. Then four representative microplasma configurations were categorized, and the proper selection of configuration was summarized in light of different conditions. Finally the synthesis, mechanism and application of some typical nanomaterials were introduced