Spontaneous Deposition of Pd Nanoparticles on Single Wall Carbon Nanotubes as an Electrocatalyst for Methanol Fuel Cell

Direct methanol fuel cell (DMFC) has attracted great attention in portable devices and transportation applications because of its high energy density, low cost, and easiness intransportation and storage [1]. A great deal of interest has been focused on the choice of Pd-based catalyst because it has a good electro activity for methanol oxidation in alkaline media [2]. Pd catalysts can overcome the CO-poisoning effect and thereby yield high performance in DMFCs.In order to improve catalytic properties of nanoparticles and minimize the overall cost of fuel cell, Pd nanoparticles (PdNPs) are deposited on several materials such as carbon supports. Functionalized carbon nanotubes (FCNTs) with many oxygen-containing functional groups (suchas carboxyl and hydroxyl groups) are getting more attractive as a support material for Pd nanoparticles [3]. The immobilization of metal nanoparticles on nanotubes is of interest to obtain nanoparticles/nanotube hybrid materials with useful properties [4]. In this work, thenanocomposite of PdNPs on single wall carbon nanotube (SWCNT) was prepared by a facile spontaneous reduction method without using any reducing agent. SWCNT-supported Pd(PdNPs/SWCNT) was decorated on carbon ceramic electrode (PdNPs/SWCNT/CCE) and used as electrocatalyst for oxidation of methanol in alkaline media. PdNPs/SWCNT nanocomposite was characterized by scanning electron microscopy (SEM), high resolution transmission electronmicroscopy (HRTEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX).Electrochemical studies including cyclic voltammetry and chronoamperometry were used to study electrochemical properties of obtained electrocatalyst. The effects of some experimentalfactors such as methanol concentration, scan rate, the upper limit of potential scanning region andlong-term stability of electrode were investigated. It was found that PdNPs/SWCNT/CCE was catalytically more active than Pd nanoparticles decorated on CCE without any support. On the other hand, the PdNPs/SWCNT/CCE catalyst has satisfactory stability and reproducibility forelectrooxidation of methanol when stored in ambient conditions and improve catalytic activity in continues cycling makes it more attractive for fuel cell applications.

کلیدواژه ها:

Electrocatalyst ، Pd nanoparticle ، SWCNT ، Carbon-ceramic electrode ، Methanol fuel cells