전해질 연료전지용 나노구조를 가진 산소 환원 촉매 개발

Abstract

A proton exchange membrane fuel cell (PEMFC) is one of candidates for replace the fossil-fueled system due to its high efficiency and eco-friendly energy device. In the PEMFC, Platinum (Pt) is used a main source as a catalyst due to its high activity. However, Pt has some problems, such as high-cost, low stability and oxygen reduction reaction. Therefore, it is important to develop a substitution about Pt catalysts. In this work, cobalt and iron encapsulated in nitrogen and sulfur co-doped carbon nanotubes (CoFe-NSTs) were prepared through a simple and facile pyrolysis method with different ratios between Co and Fe. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to investigate the physicochemical properties of the CoFe-NSTs. The CoFe-NSTs presented large diameters ranging from 20 to 300 nm with highly graphitized tube morphologies. From the electrochemical characterizations, the Co-NST showed the highest oxygen reduction reaction (ORR) activity among the CoFe-NSTs. Furthermore, the Co-NST was used as a support for platinum (Pt) nanoparticles to improve the activity and stability of the Pt catalyst. The Pt deposited on the Co-NST (Pt/Co-NST) synthesized by a facile microwave-assisted polyol method showed the well-dispersed Pt nanoparticles. The Pt/Co-NST demonstrated strong interaction between the Pt nanoparticles and the Co-NST, which was confirmed by the XPS. As a result, the Pt/Co-NST presented xx times higher ORR activity at 0.9 V compared to that of the commercial Pt/C. In addition, the Pt/Co-NST showed enhanced stability owing to the graphitized structure of the Co-NST. Therefore, the hybridization of the heteroatom-doped carbon and the Pt can be one of promising ORR catalysts to alter the commercial Pt/C.