Effect of NaBH4 concentration on the characteristics of PtRu/C catalyst for the anode of DMFC prepared by the impregnation method

PtRu/C catalysts were prepared using an aqueous co-impregnation method with NaBH4 as a reducing agent. In order to investigate the effect of the reducing agent concentration, metal ions were reduced in different NaBH4 concentrations for which the molar ratios of NaBH4 to metal ions were controlled to 1, 2, 5, 15, 50, and 250. The electrochemical properties were studied by cyclic voltammetry in a 0.5 M H2SO4 solution. The surface compositions and oxidation states of the catalysts were observed by X-ray photoelectron spectroscopy (XPS). According to the X-ray diffraction (XRD) results, Pt (fee) peak shifts were observed and crystal sizes were calculated. The electro-catalytic activities of the prepared catalysts for methanol electro-oxidation were estimated using linear sweep voltammetry. Unit cell tests were carried out to compare the direct methanol fuel cell performances. The NaBH4 concentration was found to affect the dispersion and the surface composition of the prepared PtRu particles. Optimum molar ratios of NaBH4 to metal ions were 5 and 15 for methanol electro-oxidation. (C) 2007 Elsevier B.V. All rights reserved.