(404b) Overpotential Analysis of Low Loading Pt/C Electrodes Developed By Reactive Spray Deposition Technology

According to the United States Environmental Protection Agency, 28% of greenhouse gas emitted in the United States is the result of transportation [1]. Lately, there has been a significant focus from industry to develop green technology for transportation. In particular, hydrogen fuel cell vehicles have become a major focus. As fuel cell and electrolyzer technologies become more mature and more hydrogen fueling stations are constructed nationwide, fuel cell vehicles can become a more viable green transportation method.

However, for fuel cell vehicles to become a viable transportation option in the future, additional research is required. Fuel cells will need to be optimized for the low humidity operating conditions required for automotive applications. One method to achieve this is to adjust the ionomer used in electrode fabrication. With these parameters that need to be improved, additional research should be performed to further decrease the costs associated with fuel cell manufacturing. One such fuel cell fabrication method is Reactive Spray Deposition Technology (RSDT). RSDT is a one-step flame-based process which produces platinum from the primary flame from a precursor solution while simultaneously incorporating a carbon/ionomer slurry from secondary spray nozzles. The resulting Pt/C mix is directly deposited onto proton exchange membranes to create catalyst-coated membranes (CCMs) without an additional drying step. Previous work by Yu et al examined the use of RSDT to create low Pt loading electrodes for fuel cell applications [2].

In order to improve the fuel cell performance at low humidity conditions, it is important to examine a change in ionomer. In traditional proton exchange membrane (PEM) fuel cells, it is common to use a Nafion membrane and Nafion ionomer. However, shortening the side chain length from standard Nafion 1100EW ionomers has shown to have the potential to improve the fuel cell performance at low relative humidity. This work will examine various equivalent weight Nafion and Solvay ionomers and their effect on fuel cell performance at low humidity.

The work presented will use the RSDT process to fabricate Pt/C electrodes with baseline materials as well as varying ionomer intended to improve the performance of the fuel cell at low humidity conditions. In addition, this work will look to analyze the electrochemical data by utilizing the six-step overpotential analysis technique used by Yu et al to examine how these changes affect the contributions from the different polarization sources [2, 3]. We will also look to compare the results of this overpotential analysis with the distribution of relaxation times information determined from electrochemical impedance spectroscopy in order to get a more complete understanding of how the changes in ionomer will impact the fuel cell performance, where the voltage loss occurs and how to further optimize the fuel cells for automotive applications.

References

[1] U.S. EPA. “Sources of Greenhouse Gas Emissions” www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions

[2] H. Yu, L. Bonville, R. Maric. Journal of the Electrochemical Society, 165, 5 (2018).

[3] H. Yu, L. Bonville, R. Maric. Journal of the Electrochemical Society, 165, 15 (2018).