Improved catalytic activity of mixed platinum catalysts supported on various carbon nanomaterials

Abstract

Electrocatalyst support affects not only catalytic activity of a catalyst, but also mass transportation and electron transfer in the catalyst layers of an electrode for proton exchange membrane fuel cells. Multi-dimensional and combined carbon materials such as Vulcan XC-72, carbon nanotubes (CNTs), and home-made coiled carbon nanotubes (CCNTs) are applied to enhance the catalyst activity and utilization. Three-dimensional CCNTs with large specific surface area and graphitic characteristic are synthesized by solid-state catalytic method. This obtained CCNTs and commercial CNTs are used as support to prepare platinum catalysts via modified ethylene glycol method, respectively. And the electrochemical surface areas (ECSAs) of the as-prepared Pt/CNTs, Pt/CCNTs and commercial Pt/C (JM) catalyst are evaluated by cyclic voltammetry. Then each two and three kinds of above catalysts mixed with different mass ratios are investigated. The ECSAs of Pt/C–Pt/CCNTs (95:5) and Pt/C–Pt/CNTs–Pt/CCNTs (80:10:10) are calculated to be 106 m2 gPt−1 and 111 m2 gPt−1, with respect to 70 m2 gPt−1 of Pt/C (JM) catalyst. And these mixed catalysts also demonstrate improved oxygen reduction reaction activities. This is mainly attributed to the unique structure of CCNTs, which can construct a multi-dimensional network to facilitate the mass transportation and electrons/protons transfer.