Durability of the catalyst materials is one of the issue hindering widespread commercialization of fuel cell vehicles because durability is the problem not only for the product life, but also for product cost. Carbon corrosion of the electrode materials such as catalyst support and MPL is one of the causes of performance fading, so that much more stable catalyst support material is indispensable to improve the durability [1]. So far we have developed Magneli-phase titanium oxide supported Pt catalysts as corrosion-resistant PEFC electrocatalysts at higher potentials, however catalyst activity was unsatisfactory [2]. To improve ORR activity of Pt/Ti₄O₇ catalysts further, alloying Pt with transition metal such as Ni and Co is effective and commonly used way for carbon-supported catalysts. In this work, we report Pt-Ni or Co alloy catalysts deposited on the corrosion-resistant Ti₄O₇ supports. Sub-stoichiometric titanium oxide was prepared by pulsed UV laser technique [2], and Pt-alloy catalyst particles were prepared by conventional impregnation/reduction method. From SEM and XRD results, it was found that deposited alloy particles were ordered Pt₃Ni/Pt₃Co phase with particle diameter of 5-20 nm. Half-cell study revealed that Pt₃Ni/Ti₄O₇ shows increased ORR activity (0.80 mA cm^-2_Pt @0.9 V in 0.1 M HClO₄, 25^oC) compared to commercial Pt/C catalyst (TKK TEC10V40E, 0.36 mA cm^-2_Pt). MEA with Pt₃Ni/Ti₄O₇ cathode was also examined, and confirmed the improved ORR activity. To examine the stability against higher potentials under MEA condition, accelerated stress test (AST) for start-up/shut-down was conducted according to FCCJ protocol. Similar to the Pt/Ti₄O₇ catalysts [2], improved stability of Ti₄O₇-supported Pt₃Ni was also demonstrated. Detailed physicochemical properties of the prepared catalyst and stability of the cell performance will be discussed at the meeting.

Reference

1) T. Arai, T. Ozaki, K. Amemiya, T. Takahashi, SAE International Journal of Alternative Powertrains, Vol. 6(1), (2017).

2) T. Ioroi, T. Akita, M. Asahi, Y. Yamazaki, Z. Siroma, N. Fujiwara, K. Yasuda, J. Power Sources, 223, 183 (2013).