Autoxidation of Formaldehyde with Oxygen-A Comparison of Reaction Channels.

The autoxidation of formaldehyde through initiation by triplet oxygen is studied via two initial steps: (1) H-atom abstraction and (2) 3O2 addition reaction. The reaction energy profiles show that the reactions are thermodynamically and kinetically demanding. A comparison of the pathways of these initial reactions and the search for a less energy-demanding pathway is presented. The presence of a Brønsted acid has no effect on the energetics of the reaction, while the presence of a single water molecule catalyst enhances the initial reactions. The H-atom abstraction reaction from formaldehyde results in formyl and hydroperoxy radicals. These radicals on further reaction with the second equivalent of 3O2 lead to a CO + 2HO2 product channel. The 3O2 addition reaction to formaldehyde results in a triplet biradical intermediate which further leads to performic acid, the precursor in the synthesis of carboxylic acids from aldehydes. In the presence of water molecules, performic acid is formed in a single kinetic step, and this leads to a CO2 + OH + HO2 product channel upon subsequent reaction with 3O2 in a thermodynamically favorable reaction. The results show that the less established 3O2 addition reaction to aldehydes is a viable route for autoxidation in the absence of purpose-built initiators, in addition to the well-established H-atom abstraction route.

Nanoreactor of Nickel-Containing Carbon-Shells as Oxygen Reduction Catalyst.

A Pt-free nanoreactor, consisting of N-doped hollow carbon nanocapsules with encapsulated Ni nanoparticles, is developed for high-performance oxygen reduction reaction (ORR) catalyst. The nanoreactor effect improves its catalytic activity for ORR mainly in a 4e- pathway. The presence of Ni nanoparticles within the nanoreactor significantly enhances the stability with a current retention of 90% after 40 h.

Fabrication of Phenanthroline Modified Graphene Nanosheets Decorated with Palladium Nanoparticles.

Palladium nanoparticles decorated modified reduced graphene oxide (RGO) composite was synthesized by a two-step process using 1,10-Phenanthroline (PHEN) as bridging agent. Firstly, the graphene oxide (GO) was non-covalently modified with the PHEN molecules through π-π interaction between two components. Then, the modified GO was complexed with Pd precursor and subsequently reduced from Pd2+ to Pd0 using NaBH4 to yield Pd dispersed modified RGO sheets. The structure and morphology of the resulting composites were characterized by FTIR, TGA, EDX, FESEM, HRTEM and XRD measurements. XPS results revealed that the reduction of Pd2+ to metal-lic Pd was successfully achieved, while the HRTEM and FESEM micrographs suggested that the Pd nanoparticles were well-dispersed on the functionalized graphene sheets.

A comparative study of supercapacitive performances of nickel cobalt layered double hydroxides coated on ZnO nanostructured arrays on textile fibre as electrodes for wearable energy storage devices.

We demonstrated an efficient method for the fabrication of novel, flexible electrodes based on ZnO nanoflakes and nickel-cobalt layered double hydroxides (denoted as ZnONF/NiCoLDH) as a core-shell nanostructure on textile substrates for wearable energy storage devices. NiCoLDH coated ZnO nanowire (denoted as ZnONW/NiCoLDH) flexible electrodes are also prepared for comparison. As an electrode for supercapacitors, ZnONF/NiCoLDH exhibits a high specific capacitance of 1624 F g(-1), which is nearly 1.6 times greater than ZnONW/NiCoLDH counterparts. It also shows a maximum energy density of 48.32 W h kg(-1) at a power density of 27.53 kW kg(-1), and an excellent cycling stability with capacitance retention of 94% and a Coulombic efficiency of 93% over 2000 cycles. We believe that the superior performance of the ZnONF/NiCoLDH hybrids is due primarily to the large surface area of the nanoflake structure and the open spaces between nanoflakes, both of which provide a large space for the deposition of NiCoLDH, resulting in reduced internal resistance and improved capacitance performance. Our results are significant for the development of electrode materials for high-performance wearable energy storage devices.

Water soluble graphene oxide/poly(1-vinylimidazole) composites: synthesis and characterization.

Modified graphene oxide/poly(1-vinylimidazole) (mGO/PVIm) composites were prepared via surface-initiated free radical graft polymerization. First, the hydroxyl-enriched GO sheets were functionalized with 3-methacryloxypropyltrimethoxysilane to introduce active-vinyl groups on the GO surfaces. Subsequently, 1-vinylimidazole was chemically grafted and polymerized in the presence of mGO. The chemical structures and morphology of the covalently bonded composites were characterized using FTIR, XPS, TGA, HRTEM, FESEM and XRD measurements. The mGO/PVIm composites exhibit a stable dispersion in water and show high storage stability (>10 days). Furthermore, the morphological analysis showed that mGO was homogeneously dispersed in the polymer matrix.

Noncovalent grafting of poly(3-octylthiophene) at the edges of the graphene nanosheets.

Noncovalent functionalization of graphene was carried out via in-situ oxidative polymerization of poly(3-octylthiophene) (P3OT). First, graphene sheets were prepared by a modified Hummer's method and subsequently reduced with hydrazine monohydrate. The structure and morphology of the composites were investigated by using FTIR, XPS, EDX, TGA, HRTEM, FESEM and XRD measuments. The results obtained from spectroscopic studies confirm the reduction of graphite oxide to graphene. UV-Vis and photoluminescence spectroscopies were also used to prove the doping function of the graphene in the composites. Dispersion stability indicates the good mixing between graphene and the polymer due to pi-pi interaction between two components. Scanning electron microscopy results suggest that the graphene sheets were well dispersed in the polymer matrix. The UV-Vis spectra of graphene/P3OT composites show a red shift by a few nanometers, while the emission spectra show a small blue shift. However, the nanocomposites retained the photoluminescence property of as synthesized P3OT.

Preparation and characterization of graphene/poly(diphenylamine) composites.

Nanocomposites of graphene nanosheets and poly(diphenylamine) (graphene-PDPA) were synthesized via the in-situ oxidative polymerization of diphenylamine in a sulphuric acid medium. First, graphite oxide (GO) was prepared by oxidation of natural graphite using the modified Hummer's method and subsequently reduced using hydrazine monohydrate. The as-prepared graphene sheets were noncovalently grafted with PDPA using ammonium peroxydisulphate as an oxidant. During the polymerization, graphene sheets were homogeneously dispersed in the PDPA matrix. The formation of the hybrid material was confirmed by FTIR, XPS, TGA, HRTEM, FESEM and XRD measurements. XPS analysis revealed the removal of oxygen functionality from the GO surface after reduction and the bonding structure of the reduced hybrids. In addition, the nanocomposites showed better thermal properties due to the intrinsic property of the graphene sheets.

Fabrication and characterization of graphene/poly(p-phenylenediamine) hybrids.

Graphene nanosheets functionalized with poly(p-phenylenediamine) (PPDA) were prepared via the in-situ chemical oxidative polymerization using potassium persulphate as a catalyst. Graphene nanosheets were previously prepared by chemical reduction of exfoliated graphite oxide. The structure and morphology of the composite material were characterized by FTIR, XPS, HRTEM, FESEM and XRD, while the thermal and electrical properties were measured by TGA and a four-probe method. FESEM and HRTEM observations indicated that the graphene sheets were encapsulated in the PPDA matrix. Furthermore, the nanocomposites exhibited improved conductivity and thermal stability as compared with pure PPDA.