Synthesizing Highly Active and Stable Electrocatalyst for PEMFC through Composite the Carbon-Titanium Dioxide

Abstract

Fuel cell is one of the most promising electrochemical energy conversion devices which withholds many advantages; high efficiency, high power density, rapid start up, any significant pollutant, etc. Especially, polymer electrolyte membrane fuel cell (PEMFC) has been shown a lot of attention due to its high power density and relatively good portability. Commonly, Pt/C catalyst used as PEMFC catalyst because it has high surface area, high electrical conductivity, and appropriate pore structure. However, carbon support materials suffer from degradation in a harsh operation conditions. Generally, carbon corrosion is occurred on the surface and it makes vacancies under the Pt nanoparticles. This mechanism gives rise to agglomeration and sinter of Pt particles via Ostwald ripening. Consequentially, carbon corrosion brings decreases of the electrochemical surface area (ECSA) and hinder long-term operations. Thus, electrochemically stable support materials need to be developed. Recently, some researchers focus on the metal oxide support as promising materials due to their excellent mechanical strength and inherently higher corrosion resistivity. In these alternative material candidates, TiO2 support shows an excellent durability under severe acidic condition, which provides the possibility to directly use as a support. However, hindrances such as low electrical conductivity, catalytic activity and surface area limits direct usage of TiO2 as a catalyst support. In order to improve these drawbacks, we designed the new catalyst. TiO2 nanofibers are prepared by electrospinning method and platinum nanoparticles are deposited on the support by microwave-assisted polyol method. Lastly, CNT was winded around the catalyst surface to boost up the electrical conductivity. The newly designed CNT-Pt/TiO2 nanocatalyst shows well made a 3D network. As a results, the CNTs are placed on the TiO2 surface as an electric conducting pathway. Furthermore, we found a modified Pt electronic structure that takes advantage of the strong synergetic interactions of TiO2 nanofibers, Pt nanoparticles and winded-CNT. This structure influences on a decrease of the d-band vacancy of Pt due to electron transfer from the support, resulting in an improved oxygen reduction reaction. Therefore, the CNT-Pt/TiO2 nanofiber composite shows superior performance and durability, which is definitely distinguishable at high temperature condition of 120 oC, RH 40% compare to the commercial Pt/C.