(525b) Electrochemical Characterization of a Platinum Nanotubule Array Electrode Structure Made Via Template Nanofabrication

One dimensional nanostructures including nanowires, nanotubes, and nanorods have drawn significant for electrocatalytic applications due to potential advantages that include fewer diffusion impeding interfaces with polymeric binders, more facile pathways for electron transfer, and more effective exposure of active surface sites.  Such 1D nanostructures have been fabricated using a variety of techniques including template based methods (wetting and electrosynthesis or electrodepostion), electrospinning, deposition onto nanowire or nanofiber supports, and others.  The bulk of the published work on these nanomaterials has focused on demonstrating the viability of the nanofabrication process and describing the morphology, composition, crystal structure and other basic material properties of the nanostructures.  The potential of nanomaterials lies in their functional properties which have received less attention, at least in the area of electrocatalysis.  For this work a template wetting approach was used to fabricate an array of platinum nanotubules which were examined electrochemically with regard to the electro oxidation of ferrocyanide and formic acid.  The former has long been employed as an electrochemical standard in evaluating new electrode structures in comparison to more traditional ones.  The latter had long been used as a model compound for other small organics but has also shown great promise in fuel cell applications.  For both reactions, arrays of 100 and 200 nm nanotubules were compared to a traditional platinum black catalyst, all of which were found to have similar surface areas.  Peak formic acid oxidation current was found to be highest for the 100 nm nanotubule array, followed by the 200 nm nanotubule array and the Pt black, however CO tolerance of the three platinum electrodes was found to be nearly identical, as were the onset potentials of the oxidation and reduction peaks.  The higher current response was attributed to enhanced mass transfer in the nanotubule electrodes, likely due to a combination of both the more open nanostructure as well as the lack of a polymeric binder in the catalyst layer.  Using the ferrocyanide reaction, electron transfer coefficients were evaluated.  Faster electron transfer kinetics were observed with the Pt nanotubules than with the Pt black electrode, likely due to the reduced number of interfaces and the lack of a polymeric binder such as Nafion.