Sirvi Kuupäev , alustades "2010-05-21T13:28:25Z" järgi

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Electrocatalytic reduction of oxygen on carbon nanotube-based nanocomposite materials
(2010-05-21T13:28:25Z) Aleksejeva, Nadežda
The electrochemical reduction of oxygen on carbon nanotube (CNT)-supported gold and platinum nanoparticles modified glassy carbon (GC) electrodes has been studied using the rotating disk electrode (RDE) method. The kinetic parameters for this reaction have been determined. The reduction of oxygen was studied on GC electrodes modified with oxidatively pre-treated and untreated multi-walled carbon nanotubes (MWCNTs) in 0.5 M H2SO4. The RDE results show that oxidative pre-treatment of MWCNTs has a strong effect on the electrocatalytic activity for O2 reduction in acid solution. The results obtained in this work clearly demonstrate the effect of impurities containing in MWCNTs on the kinetics of the oxygen reduction reaction. This effect is caused by catalyst impurities (mostly iron) which remain in the nanotubes prepared by chemical vapour deposition and can be largely removed by treatment in acids. The electroreduction of oxygen has been studied on AuNP/MWCNT catalyst materials prepared by four different procedures. The AuNP/MWCNT catalyst showed a pronounced electrocatalytic activity towards O2 reduction in acid media. The results clearly demonstrated that MWCNTs can be used as support for a three-dimensional electrocatalytic layer containing a dispersed metal that specifically catalyses the reduction of oxygen to hydrogen peroxide. These nanocomposites were simple to construct and their electrochemical response was stable during long-term testing. PtNP/CNT composite materials were prepared using two different synthetic routes. Transmission electron microscopy experiments revealed that the amount of platinum deposited onto the treated carbon nanotubes support is sufficient although some of the Pt particles are agglomerated. Soft electrochemical decontamination, which is able to clean the samples without altering the initial properties of platinum nanoparticles, was performed using CO stripping. The PtNP/CNT catalysts exhibited promising electrocatalytic activity for oxygen reduction to produce H2O through a four-electron reduction pathway with high stability. The RDE results were rather similar for all the PtNP/CNT modified electrodes studied.