Electrochemical Characterization of Hydrothermally Synthesized Pt-Ru-Ni-P Catalyst for Direct Methanol Fuel Cell

Abstract

Pt-Ru-Ni-P/multiwalled carbon nanotube (MWCNT) catalyst is synthesized by a hydrothermal process using sodium hypophosphite (NaH2PO2) as a reducing agent. The particle size is evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrocatalytic activity of a Pt-Ru-Ni-P/MWCNT catalyst for methanol electro-oxidation has been studied by cyclic voltammetry, chromoamperometry, and impedance spectroscopy. TEM images reveal that the Pt- Ru- Ni-P nanoparticles have a wide size distribution with an average size of 3.2 nm. Pt-Ru- Ni- P/MWCNT catalyst shows an electrochemically active surface area of 63.2 m(2) g(-1) and a mass activity of 187.56 mA mg Pt-1. It has been found that the presence of phosphorus as an interstitial species can enhance the dispersion as well as reduce the size of Pt-Ru-Ni-P nanoparticles. Moreover, incorporation of phosphorus into the Pt-Ru-Ni/MWCNT catalyst shows a 1.5 times higher electrocatalytic activity. The power density (57 mW cm(-1)) of the Pt-Ru-Ni-P/MWCNT catalyst in fuel cell tests is higher than that (40 mW cm(-1)) of the Pt-Ru-Ni/MWCNT catalyst. (c) 2013 The Japan Society of Applied Physics