Martin G. Bakker

NanoCOT: Low-Cost Nanostructured Electrode Containing Carbon, Oxygen, and Titanium for Efficient Oxygen Evolution Reaction.

Developing high-efficiency, durable, and low-cost catalysts based on earth-abundant elements for the oxygen evolution reaction (OER) is essential for renewable energy conversion and energy storage devices. In this study, we report a highly active nanostructured electrode, NanoCOT, which contains carbon, oxygen, and titanium, for efficient OER in alkaline solution. The NanoCOT electrode is synthesized from carbon transformation of TiO2 in an atmosphere of methane, hydrogen, and nitrogen at a high temperature. The NanoCOT exhibits enhanced OER catalytic activity in alkaline solution, providing a current density of 1.33 mA/cm(2) at an overpotential of 0.42 V. This OER current density of a NanoCOT electrode is about 4 times higher than an oxidized Ir electrode and 15 times higher than a Pt electrode because of its nanostructured high surface area and favorable OER kinetics. The enhanced catalytic activity of NanoCOT is attributed to the presence of a continuous energy band of the titanium oxide electrode with predominantly reduced defect states of Ti (e.g., Ti(1+), Ti(2+), and Ti(3+)) formed by chemical reduction with hydrogen and carbon. The OER performance of NanoCOT can also be further enhanced by decreasing its overpotential by 150 mV at a current density of 1.0 mA/cm(2) after coating its surface electrophoretically with 2.0 nm IrOx nanoparticles.

Highly efficient nitrogen-doped hierarchically porous carbon supported Ni nanoparticles for the selective hydrogenation of furfural to furfuryl alcohol

Nickel nanoparticles supported on nitrogen doped hierarchically porous carbon (Ni/CN) are found to be highly efficient and reusable catalysts for the selective hydrogenation of biomass-derived furfural to furfuryl alcohol (FA). Various characterization methods were used to study the structural and morphological features of the catalysts. Furfural conversion of 96% and 95% FA selectivity was obtained using a 5 wt% Ni/CN catalyst. This catalyst showed excellent recyclability without any loss in activity and FA selectivity when it was reused four times. The higher catalytic performance is attributed to the nitrogen incorporated hierarchical porous 3D carbon network.

An electron spin resonance investigation of the products of the Friedel–Crafts reaction of sulphur dioxide with methylnaphthalenes

A series of mono-, di-, tri-, tetra-, and hexa-methylnaphthalenes, and naphthalene were reacted with AlCl3–SO2, AlCl3–SOCl2, or AlCl3–S2Cl2, using CH2Cl2 as solvent. The radical cation products produced were studied using e.s.r. 1,4-, 1,5-, and 1,8-dimethyl-, 1,2,4-trimethyl-, 1,2,3,4- and 1,3,5,7-tetramethyl-, 1,2,3,4,5,8-hexamethyl-, and octamethyl-naphthalene all gave predominantly spectra from the monomer cation radical. Naphthalene, 1- and 2-methyl- and 1,3-, 1,6-, 1,7-, 2,3-, 2,6-, and 2,7-dimethylnaphthalene gave predominantly spectra ascribed to methyl derivatives of naphtho[1,8-cd]-1,2-dithiole. Spectra from these compounds also contained a significant component which was ascribed to methylperylenes formed from the Scholl condensation of the parent compound. A species described as 3H, 10H-acenaphtho[1,2-c]-1,2-dithiete was observed as a minor product in the reactions with 1,8-dimethylnaphthalene.

Surfactant aggregates (solloids) adsorbed on silica as stationary chromatographic phases: structures and properties

The structure and physical properties of solloids (surfactant aggregates adsorbed on surfaces) adsorbed on particles are of general interest. The relationship between solloid structure and properties of hexadecyltrimethylammonium bromide (HTAB), cetylpyridinium chloride (CPC) and cetylpyridinium salicylate (CPS) adsorbed on silica particles was studied by electron paramagnetic resonance (EPR) spectroscopy using the spin-probes peroxylaminedisulfonate (PADS) and 4-[N,N-dimethyl-N-(n-hexadecyl)ammonium]-2,2,6,6-tetramethylpiperidin yl-N-oxy bromide (HTAB*). Using HTAB* incorporated in HTAB, CPC and CPC solloids and comparing the results to those in micelles, it was determined that for silica around pH 4 the solloids are very similar in properties to the micelles. This is consistent with a linear solvation-energy relationship (LSER) analysis of solute equilibration data which indicates that at pH 5 HTAB solloids have similar properties to HTAB micelles. The PADS spin-probe appears to be more sensitive to changes in the properties of the double layer, and substantial differences were observed between HTAB, CPC and CPS and as a function of HTAB concentration for HTAB solloids on silica.

Hierarchically porous monoliths of carbon and metal oxides with ordered mesopores

Abstract Hierarchically porous carbon and metal oxide materials offer great benefits in separations, catalysis and renewable energy. We have here used hierarchically porous silica monoliths with ordered mesopores as hard templates to produce nanocast carbon, Co3O4, and NiO monoliths with similar structures. Besides providing the materials with more well-defined physicochemical properties, the ordered mesopore structure also offers an excellent model system for investigating the nanocasting process in detail. The mesopores of the silica monoliths were first infiltrated with furfuryl alcohol or metal nitrate precursor solutions, which subsequently could be thermally converted to carbon or the corresponding metal oxides. After the silica scaffolds have been removed by etching in base solutions, the resulting replica monoliths display macroscopic morphology and macropore structure similar to the original silica template. However, while the carbon and Co3O4 materials both display a well-organized nanowire structure, giving rise to high surface area and narrow pore size distribution, the NiO monoliths exhibit a significantly lower surface area and less well-defined mesopore structure implying that only part of the silica mesopores has been replicated. We believe this apparent difference between the two metal oxides is a consequence of differences in mass transport.

New conducting polymers: PF6-doped XYZ-triheterocycles based on X, Y, Z= thiophene, furan and n-methylpyrrole☆

Abstract A number of triheterocycles XYZ, where X, Y, Z = furan (O), thiophene (S), or N-methylpyrrole (N) were prepared, and the polymers, obtained by oxidizing them with NOPF6, were studied by four-probe DC conductivity and EPR. SSS has a conductivity of 2.4 S cm−1 at room temperature, and 0.0075 spin/triheterocycle, while SOS has a conductivity of 0.2 S cm−1 and 0.15 spins/triheterocycle; both have narrow Lorentzian EPR lineshapes. The other samples had conductivities below the measurement threshold (10−5 S cm−1). We postulate that NOPF6 overoxidized the polymers, thereby creating more bipolarons than polarons, and reducing the number of charge carriers.

Electrodeposition of cobalt nanowires on H-terminated conductive Si(111) surfaces using coblock polymer templating

The authors have investigated the formation of block copolymer nanocavities on H-terminated conducting Si(111) surfaces as templates for the electrochemical growth of perpendicular metallic nanowire arrays. Poly(styrene)-block-poly(methyl methacrylate) block copolymers (PS-b-PMMA) of appropriate block length and PS to PMMA ratio were used to create a self-assembled array of perpendicular nanocavities in which the PS majority phase is continuous and surrounds cylinders of the minority PMMA phase. Here, we report that H-terminated conducting Si(111) surfaces are also capable of inducing a perpendicular orientation in block copolymers, which—in all likelihood—is a direct result of the H-termination (i.e., removal of the oxide layer). Atomic force microscopy reveals that an acetic acid wash of the annealed block copolymer causes the minority PMMA component to be rearranged, giving rise to cavities that are perpendicular to the conducting Si substrate. Subsequently, scanning electron microscopy reveals that el...

The effect of inclusion inβ-cyclodextrin on the chemistry of peroxides: Reactions of radicals withβ-cyclodextrin

Studies by electron paramagnetic resonance (EPR), differential scanning calorimetry, thermogravimetric analysis, HPLC and NMR showed that radicals produced by thermolysis and photolysis of benzoyl peroxide,t-butyl peroxide and cumene hydroperoxide included inβ-cyclodextrin (β-CD), undergo significant reaction with theβ-CD. The formation ofβ-CD radicals was observed by EPR. Products formed by addition of radicals toβ-CD were also observed. Such host:guest radical reactions explain the reported stabilization of peroxides, found withβ-CD inclusion, as being primarily due to the interruption of chain reactions by trapping of the chain carriers. A small increase in activation barrier for cleavage of the included peroxide inβ-CD was also observed.

Synthesis, electrical conductivity and electron paramagnetic resonance spectroscopy of polymers derived from NOPF6-doped XYZ-triheterocycles based on pyrrole, furan and thiophene

A series of triheterocycles; [graphic omitted] for X, Y, Z = OOO, SSS, SOS, SSO, OSO, SOO, O(N-Me)O, S(N-Me)O and S(N-Me)S have been synthesised; of these O(N-Me)O, SOO and S(N-Me)O are new. The triheterocycles were chemically polymerised and oxidised with NOPF6. Only the polymers derived from SSS, SOS and SSO show appreciable conductivities. EPR studies indicate the presence of polarons in SSS, SOS, SSO and, at lower concentrations, in OOO. All the samples appear to show an easily saturable EPR signal assigned to localised radicals. In OSO, SOO, O(N-Me)O, S(N-Me)O and S(N-Me)S this signal displays considerable asymmetry, and g-values significantly above the free electron value. S(N-Me)S shows a higher g-value consistent with a loss of planarity.

Development of ultrahigh surface area porous electrodes using simultaneous and sequential meso- and micro-structuring methods

Very high surface area nanostructured metal electrodes are of interest as efficient current collectors. For thin film devices, the nanostructured metal can be grown in place using electrodeposition or electroless deposition. For larger devices metal electrodes structured at more than one length scale are desirable. Self-assembling surfactant templates are a versatile method of generating a range of nanostructures. As we report here, electrodeposition of nickel, cobalt and copper from liquid crystalline solutions of Triton X-100 produces a number of nanostructures, with significant surface area increases. Electrodeposition into templates with microstructure has proven more demanding. Oil-in-water Microemulsions of Tween surfactants and soy oil, produce micrometer scale structures, however measured nickel surface area does not scale with sample thickness. The method is also not robust, and was found to give microstructures only for nickel and cobalt. Experiments show that under our conditions a combination of nickel metal, nickel acetate and nickel/detergent microstructures are formed. Member Price: