Enzyme Electrode Platform Using Methyl Viologen Electrochemically Immobilized on Carbon Materials

This paper presents the electrochemical stabilization of methyl viologen cations on a variety of carbon materials using a glassy carbon electrode. Three different types of voltammetry (potential hold, triangular wave, and square wave voltammetry) were used to stabilize the methyl viologen cation. Methyl viologen cation-modified multi-walled carbon nanotubes (MWCNTs) of different diameters and with various functional groups were examined to observe the effects of carbon particle size and surface modification. Various carbon materials containing MWCNTs, acetylene black, Super P, Vulcan XC-72, and Ketjenblack were modified by methyl viologen and then electrochemically characterized. Their electrochemical behaviors are discussed in terms of carbon properties, such as pore structure and electrical conductivity. Carbon with immobilized the methyl viologen cation and glucose oxidase was assessed to confirm its feasibility for enzyme electrode applications.clos

Enzymatic coproduction of biodiesel and glycerol carbonate from soybean oil in solvent-free system

The enzymatic coproduction of biodiesel and glycerol carbonate by transesterification of soybean oil and dimethyl carbonate (DMC) has been studied in a solvent-free system. The effects on biodiesel and glycerol carbonate conversion of reaction conditions including the kind of enzyme, the amount of enzyme, the molar ratio of DMC to soybean oil, the reaction temperature, and water addition were investigated. The optimal conditions for biodiesel and glycerol carbonate were 20% Novozym 435, 10:1 molar ratio of DMC to soybean oil, and 0.7% water addition. Under these conditions, the conversions of 96.4% biodiesel and 92.1% glycerol carbonate have been achieved after 48 h.clos

Electro-biocatalytic production of formate from carbon dioxide using an oxygen-stable whole cell biocatalyst

The use of biocatalysts to convert CO2 into useful chemicals is a promising alternative to chemical conversion. In this study, the electro-biocatalytic conversion of CO2 to formate was attempted with a whole cell biocatalyst. Eight species of Methylobacteria were tested for CO2 reduction, and one of them, Methylobacterium extorquens AM1, exhibited an exceptionally higher capability to synthesize formate from CO2 by supplying electrons with electrodes, which produced formate concentrations of up to 60 mM. The oxygen stability of the biocatalyst was investigated, and the results indicated that the whole cell catalyst still exhibited CO2 reduction activity even after being exposed to oxygen gas. From the results, we could demonstrate the electro-biocatalytic conversion of CO2 to formate using an obligate aerobe, M. extorquens AM1, as a whole cell biocatalyst without providing extra cofactors or hydrogen gas. This electro-biocatalytic process suggests a promising approach toward feasible way of CO2 conversion to formate.clos

Analysis of the spatially distributed performance degradation of a polymer electrolyte membrane fuel cell stack

Herein we report the spatially uneven degradation of a polymer electrolyte membrane fuel cell (PEMFC) stack operated under load variation. Fifteen sub-membrane electrode assemblies (sub-MEAs) at various cell positions and various points within each cell were obtained from the original MEAs employed in the fuel cell stack. Polarization curves and the voltammetric charge of these MEAs were measured in order to correlate localized performances with the redistributed electrochemically active surface on Pt using the polarization technique and cyclic voltammetry. Several ex situ characterizations including electron probe microanalysis, environmental scanning electron microscopy, and X-ray diffraction were also performed to find evidence, supporting the inhomogeneous degradation of the fuel cell stack. Possible routes and processes for the non-uniform stack degradation during the PEMFC stack operation will also be discussed. Copyright ª 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.1221sciescopu