Elsevier

Materials Letters

Volume 64, Issue 10, 31 May 2010, Pages 1169-1172
Materials Letters

One-step fabrication of ordered Pt–Cu alloy nanotube arrays for ethanol electrooxidation

https://doi.org/10.1016/j.matlet.2010.02.041Get rights and content

Abstract

Novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the area of the fuel cell because of their extremely high surface-to-volume ratios and excellent activities. Here, we report the one-step fabrication of Pt–Cu alloy nanotube arrays. As determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, ordered Pt–Cu alloy nanotubes have been successfully fabricated utilizing a nanochannel alumina template. The electrocatalytic activities of the Pt–Cu alloy nanotubes for the oxidation of ethanol in acidic medium were investigated by cyclic voltammetry. The results show that the Pt–Cu alloy nanotubes can be used as effective electrocatalysts for ethanol oxidation in direct alcohol fuel cells.

Introduction

The direct alcohol fuel cell (DAFC) is a promising candidate for portable power sources, electric vehicles and transportation applications [1], [2], [3], [4]. Among the fuels, ethanol is one of the potential fuels and it can be easily produced in great quantity by fermentation of biomass. However, ethanol oxidation to CO2 is associated with the cleavage of the C–C bond, which requires higher activation energy than C–H bond breaking [5]. Pt and Pt-based catalysts have been extensively investigated as electrocatalysts for the electrooxidation of liquid fuels such as methanol and ethanol [6], [7]. However, Pt itself is known to be rapidly poisoned on its surface by strongly adsorbed species coming from the dissociative adsorption of ethanol [8], [9]. In this regard, the development of more efficient electrocatalysts for ethanol oxidation is highly desirable. One of the strategies is to develop binary or ternary alloy electrocatalysts because alloying of metals may result in important changes in their activity and poison tolerance in DAFCs [10], [11].

Recently, novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the area of fuel cell because of their extremely high surface-to-volume ratios and excellent activities. For example, Pd nanowire arrays exhibit high activity for ethanol oxidation [12]. Pt nanotubes have been used as electrocatalysts for the oxygen reduction [13]. These unsupported electrocatalysts have the potential to combine the advantages of carbon supported Pt catalysts while overcoming their drawbacks and possess high surface area, high utilization, high activity, and high durability [14]. Here, we report the fabrication of ordered Pt–Cu alloy nanotubes (PCNTs) utilizing a nanochannel alumina template by a one-step electrodeposition method. We demonstrate that the PCNTs can be used as effective electrocatalysts for ethanol oxidation in direct alcohol fuel cells.

Section snippets

Experimental

Nanochannel alumina (NCA) templates were prepared by anodizing high purity aluminum foils. In order to electrodeposit Pt–Cu alloy, a gold film with about 5 nm thickness was deposited on one side of the NCA template as electrode by using a vacuum evaporation apparatus. PCNTs were deposited from a 0.5 M H2SO4 solution containing 5 g/l K2PtCl4 and 12 g/l CuSO4 by using a galvanostatic method. The cathode current density was kept at 100μAcm 2. All electrochemical deposition and electrochemical

Results and discussion

Fig. 1a shows the SEM image of the NCA template with a pore diameter of about 250 nm. Fig. 1b shows the SEM image of the surface view of the free-standing PCNTs with a length of about 800 nm after completely dissolving the NCA template. The inset shows the enlarged image of the PCNTs. It can be seen that the PCNTs replicate the pore sizes and shapes. The diameter and wall thickness of the PCNTs are about 250 nm and 45 nm, respectively. The XRD spectrum of PCNTs is shown in the inset of Fig. 1c. The

Conclusions

In conclusion, PCNTs with diameters of 250 nm have been successfully fabricated by one-step direct electrodeposition. The PCNTs exhibit good stability and catalytic activity for ethanol oxidation and show promise to be a new type of supportless electrocatalyst in direct alcohol fuel cells.

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