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Dobrzeniecka A.,Ruhr University Bochum | Dobrzeniecka A.,University of Warsaw | Zeradjanin A.R.,Ruhr University Bochum | Zeradjanin A.R.,Center for Electrochemical science | And 6 more authors.
Catalysis Today

An advanced approach based on scanning electrochemical microscopy (SECM) was used to investigate the kinetics of the oxygen reduction reaction (ORR) on multiwalled carbon nanotubes (MWCNTs) and a composite of MWCNTs and cobalt (IX) protoporphyrin (MWCNTs/CoP). The amount of hydrogen peroxide produced during ORR was studied as a function of catalyst loading in an electrolyte of pH 7. Additionally, a Pt ultra microelectrode (UME) was used to determine changes in interfacial oxygen concentration from which intrinsic rate constants of heterogeneous electron transfer during the ORR were calculated. The amount of hydrogen peroxide produced and the number of electrons exchanged during oxygen reduction, and the heterogeneous electron transfer rate constants determined using SECM were compared with the corresponding values obtained using methods based on forced convection, namely RRDE and RDE. It was found that SECM offers some advantages compared to RDE or RRDE with regard to accuracy in determining the number of electrons transferred during the ORR, particularly in the case of thick and porous catalyst films. However, the heterogeneous electron transfer rate constants were similar for both methods, indicating that the determination of the surface concentration of reactants using RC-SECM suffers from some drawbacks. © 2015 Elsevier B.V. Source

Wang Z.,CNRS Laboratory of Physical Chemistry and Microbiology for the Environment | Etienne M.,CNRS Laboratory of Physical Chemistry and Microbiology for the Environment | Poller S.,Center for Electrochemical science | Schuhmann W.,Center for Electrochemical science | And 3 more authors.

Multiwalled carbon nanotubes (MWCNT) have been functionalized, for the electrocatalytic detection of NADH, by microwave treatment, electrochemical deposition of poly(methylene green) or wrapping with an Os-complex modified polymer. Sol-gel thin films have been then electrodeposited on the carbon nanotube layers for co-immobilization of D-sorbitol dehydrogenase and diaphorase when necessary and NAD + via covalent linkage using glycidoxypropyltrimethoxysilane. The comparison of these systems shows that the electrodeposited sol-gel matrix can significantly affect the operational behavior of functionalized MWCNT. Only MWCNT wrapped with the Os-complex modified polymer and covered with a sol-gel biocomposite allowed the electrochemical detection of D-sorbitol in a reagentless configuration. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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