The Role of Surface Functionalities in PtGe and PtIn Catalysts for Direct Methanol Fuel Cells

Abstract

Bimetallic PtGe and PtIn catalysts were prepared over Vulcan carbon (VC) and multiwall carbon nanotubes (NT) by conventional impregnation method (CI). These supports were functionalized with citric or nitric acid. The structural and electrochemical characteristics of the different functionalized supported catalysts were analyzed in order to determine the influence of the functional groups. The methods applied were temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), cyclohexane dehydrogenation reaction (CHD), and CO stripping. The functionalization treatment with citric or nitric acid eases CO oxidation to CO 2 , decreasing poisoning effect of CO over Pt, due to the development of oxygenated groups on support surfaces and in the nearby Ge and In. Bimetallic catalysts supported on carbons functionalized with HNO 3 present increasing electrochemical active surface values, indicating a better electrochemical behavior than the corresponding monometallic catalysts. DMFC experiments show a very good behavior of PtGe catalysts, mainly for those supported on HNO 3 -functionalized NT, reaching a maximum power density of 80 mW cm −2 . Conversely, PtIn catalysts exhibit a very poor behavior.