Abstract
In the present study, highly homogeneous platinum nanocatalysts with enhanced electrocatalytic activity were uniformly deposited on carbon nanotubes directly grown on a silicon plate (Pt/CNTs/Si) as the electrode catalysts for direct methanol fuel cells (DMFCs) by a novel homemade open-loop reduction system (OLRS). Compared with a traditional reflux system that maintains the ratio of water to ethylene glycol (EG) at ∼160°C for ∼4 h, the gradual concentration increase of EG in the precursor solution can be accomplished by distilling off water in the OLRS while increasing the temperature to 130°C. This process with simultaneous increases in precursor concentration and in reaction temperature rendered high-quality Pt nanoparticles to precipitate with a high-density dispersion on the pretreated CNTs. The OLRS is not only able to only shorten the reduction time (<1.5 h) but is also able to enhance the electrocatalytic activity of the electrodes by creating a preferential orientation of Pt (1 1 1) facets for the methanol oxidation reaction (MOR). Cyclic voltammetry and electrochemical impedance spectroscopy were conducted to evaluate the mass activity (MA) and charge transfer resistance (Rct) of the prepared electrodes for the MOR. Compared with the electrodes prepared by traditional Pt reductions (MA: 100-360 A g <sup>-1</sup> and Rct: 40-80 Ω-cm <sup>2</sup> ), the Pt/CNTs/Si-based electrodes prepared at 130°C in the OLRS exhibited superior electrocatalytic properties, including an MA of 435 A g <sup>-1</sup> and an Rct of ∼30 Ω-cm <sup>2</sup> . © 2012 Elsevier Ltd. All rights reserved.