Maha Yusuf⁺, Drew Christopher Higgins⁺, John Xu⁺⁺, Yongmin Kim⁺⁺, Tanja Graf⁺⁺⁺, Thomas D. Schladt⁺⁺⁺, Thomas F. Jaramillo⁺, Friedich B. Prinz⁺⁺

⁺Department of Chemical Engineering, Stanford University, Stanford, California, 94305, USA

⁺⁺ Department of Mechanical Engineering, Stanford University, Stanford, California, 94305, USA

⁺⁺⁺ Volkswagen Group Research, Wolfsburg, 38436, Germany 

Low-temperature fuel cells are a promising technology that converts clean and sustainable carbon-free fuels to electrical power. They are suitable for a wide-range of applications including in the transportation sector to grid-scale power generation. One of the major limitations in fuel cell technologies is the efficiency loss at the cathode due to the kinetically sluggish oxygen reduction reaction (ORR).^[1] Currently, Pt-based electrocatalysts are the most commonly used catalysts at the fuel cell cathode. However, the scarcity, high cost, and the sluggish ORR kinetics on Pt catalysts drive the need to develop alternative catalytic Pt-based electrocatalysts with better mass activity, and durability to improve the performance and lower the cost of fuel cells.^[2-3]

We have developed sputter deposition techniques to fabricate Pt and Pt-alloy based electrocatalysts with reduced precious metal contents. We particularly aim to engineer the structure, surface chemistry, and catalyst-support interactions to achieve high Pt-based mass activities and catalyst durability. In this study, we focus on leveraging the ability of sputter deposition to achieve low-loadings of Pt, with the ability to achieve control over their thicknesses and compositions ^[4-5]. The sputter deposited Pt-based catalysts are characterized by various techniques such as X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and inductively coupled plasma mass spectrometry. The catalysts are rigorously evaluated for both electrochemical oxygen reduction reaction activity, and durability using the rotating-disk electrode (RDE) technique. Our initial electrochemical testing results are promising, and show mass activities that already exceed the DOE’s 2020 target criteria of 0.44 A/mg_Pt⁶.

References:

1. Adina Morozan, Bruno Jousselme, Serge Palacin, Energy Environ. Sci., 2011, 4 (1238-1254).
2. 2. A. Brouzgou, S.Q. Song, P. Tsiakaras, Appl. Catal., B, 2012, 127 (371-388).
3. Haifeng Lv, Dongguo Li, Dusan Strmcnik, Arvydas P. Paulikas, Nenad M. Markovic, Vojislav R. Stamenkovic, Nano Energy, 2016, 29 (149-165).
4. Ryan O’Hayre, Sang-Joon Lee , Suk-Won Cha , Fritz.B Prinz, J. Power Sources, 2002, 109 (483-493).
5. Ikwhang Chang, Seunghee Woo, Min Hwan Lee, Joon Hyung Shim, Yuanzhe Piao, Suk Won Cha, Appl. Surf. Sci., 2013, 282 (463-466).
6. U.S. Department of Energy’s Multi-Year Research, Development, and Demonstration Plan 2016. Source: https://energy.gov/sites/prod/files/2016/10/f33/fcto_myrdd_fuel_cells.pdf