Electrochemical activity and durability of Pt-Sn alloys on carbon-based electrodes prepared by microwave-assisted synthesis

The microwave-assisted polyol (MP) reduction was used as the deposition technique for preparing binary Pt-Sn alloys with a mean size of 5 nm on carbon nanotubes (CNTs). A large number of CNTs with an average diameter of 40-50 nm were attached to carbon paper substrate using a catalytic chemical vapor deposition. The fast MP synthesis enabled the formation of Pt-Sn nanoalloys within 6 min. X-ray diffraction and X-ray photoelectron spectroscopy were applied to analyze the crystalline alloy structure. Postcalcination at 600 degrees C showed a positive effect in improving the activity and the long-term durability (i.e., 1000 cycles) of Pt-Sn catalysts toward the H2SO4 electrolyte, as demonstrated by cyclic voltammetry test and AC impedance spectroscopy. An equivalent circuit also was proposed to analyze the equivalent serial resistance of the electrocatalysts after the potential cycling. This improvement can be attributed to the reasons that the calcination process is prone to the following: (i) the reinforcement of the adherence between the catalyst particle and the carbon support, (ii) the transformation of crystalline phase on Pt-Sn alloy, and (iii) the decrease of Pt (II) content and chemisorbed oxygen species. The Pt-Sn crystallographic phase on the CNT-based support shows an enhanced activity and more corrosion resistance in acidic electrolyte. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.