Alemayehu Dubale Duma,a Yu-Chen, Wu a, Wei Nien Su,*b Chun-Jern Pan, a Meng-Che Tsai,a Hung-Ming Chen, Jyh-Fu Lee, Hwo-Shuenn Sheu, Van Thi Thanh Ho and Bing-Joe Hwang*ac
aNanoelectrochemistry Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan.
b2NanoElectrochemistry Laboratory, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan
3National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
e-mail:alexdubale@gmail.com Abstract
The sluggish rate of the oxygen reduction reaction (ORR) and the durability of Pt-based catalysts along with the carbon corrosion on the cathode side, have been recognized as critical issues associated with the durability of catalyst restricting their application towards wide applications for proton exchange membrane fuel cells (PEMFCs). We present herein, a synthesis of a series of highly conductive modified Titanium oxide-supported Pt catalysts and their respective electrochemical performance investigated for use in the oxygen reduction reaction. TiO2 nanoparticles were synthesized using a solvothermal method before their surface was coated by using Hexamethyldisilazane (HMDS) so as to inhibit the particle growth during the succeeding high temperature treatment under H2 environment, where they eventually transformed to Ti4O7, when the temperature rises to 1000 ℃. Structural and electronic properties of the support materials and the subsequent catalysts are characterized by various approaches, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray absorption spectroscopy (XAS). It was found that the electrical conductivity of TiO2 increases with increasing reduction temperature, but at the expense of decreased surface area. The electrochemical performance reveals that the Pt catalyst based on HMDS modified TiO2 support, which was subjected to H2 reduction at 850℃, namely (20Pt 850 FHST), exhibited better activity when compared to others in the same series with a maximum current density of 0.049 mA/cm2 at 0.9 V (vs. NHE) and an onset potential of 0.86 V (vs. NHE). The prolonged cycling test also exhibited that HMDS modified 20Pt 850 FHST catalyst possesses superior durability to commercial catalyst (JM 20 Pt/C). X-ray absorption spectroscopy (XAS) further confirms that higher electron population of Pt 5d-orbital improves the electrochemical activity in which this catalyst shows the improved performance for ORR compared to others within the series i.e. different H2 reduction temperatures.
Keywords: Oxygen reduction reaction, Fuel cell, Strong Metal Support Interaction, Titanium oxide