Effective preparation of carbon nanotube-supported Pt-Ru electrocatalysts

Carbon nanotube (CNT)-supported electrocatalysts, such as Pt/CNT and Pt-Ru/CNT, have been intensely studied recently for membrane fuel cell applications. These novel clectrocatalysts were generally prepared by chemical reduction deposition using ethylene glycol (EG) as a reducing agent. However, due to different metal deposition conditions, CNT-supported binary and multi-component electrocatalysts cannot be prepared using EG alone with satisfactory results. In this study, an effective method for preparation of CNT-supported Pt-Ru alloy electrocatalysts has been developed. Suitable amounts of sodium hydrogen sulfite (NaHSO3) and calcium hydroxide aqueous solutions were employed as additives to EG forming a modified reducing agent. This new approach was based on the use of more suitable Pt-Ru deposition environments created by the modified EG near the isoelectric point (IEP) on the acid-oxidized CNT surfaces. It gave rise to enhanced formation of Pt-Ru/CNT with high metal deposition efficiency, excellent nanoparticle morphology and desired electrocatalyst composition. In addition, the prepared Pt-Ru/CNT exhibited high methanol electrooxidation activity in 0.5 M H2SO4 aqueous solution better than that of a carbon black-supported commercial product. Overall, preparation of Pt-Ru/CNT using the modified EG resulted in much better electrocatalyst formations than those prepared using a variety of common reducing agents. (c) 2005 Elsevier B.V. All rights reserved.