Nanofibrous Electrode Design By CNT-Winded Pt/TiO₂ for Superior PEMFC Performance and Durability at High Temperature

Abstract

Fuel cell is one of the most promising electrochemical energy conversion devices that has many advantages such as high efficiency, high power density, CO2 free, noise free, rapid start up, 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. Generally, Pt supported on carbon black is used as an electrocatalyst in PEMFC. However, carbon corrosion is one of the main problem for electrode structure collapse and catalyst activity loss, which can be further accelerated at high temperature. Therefore, we need to find an alternative catalyst support material that is electrochemically stable and interacts strongly with the catalyst active sites. Recently, metal oxide supports have been reported as promising materials due to their excellent mechanical resistance and inherently higher stability. Among many candidates, titanium dioxide (TiO2) support has an extraordinary stability under severe acidic atmosphere, which provides the possibility to directly use as a support material. However, the low electrical conductivity, catalytic activity and surface area of TiO2hinder the direct apply to the PEMFC electrode. In order to solve these problems, we prepared TiO2 nanofibers by electrospinning method and platinum nanoparticles are deposited by microwave-assisted polyol method to synthesize an effective electrode catalyst. Then, CNT was winded around the catalyst surface to boost up the electrical conductivity. 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 cathode with the CNT modified Pt/TiO2 nanofiber composite shows higher catalytic activity due to the elimination of the drawback associated with conductivity and enhanced electronic active structure. As from various PEMFC tests, our CNT-Pt/TiO2 catalyst shows superior performance and durability, which is definitely distinguishable at high temperature condition of 120 oC and RH 40% compare to the commercial Pt/C.