A Comparative Study on the Activity and Stability of Iridium-Based Co-Catalysts for Cell Reversal Tolerant PEMFC Anodes
A Comparative Study on the Activity and Stability of Iridium-Based Co-Catalysts for Cell Reversal Tolerant PEMFC Anodes
Robert Marić3,1,2, Christian Gebauer1, Florian Eweiner1 and Peter Strasser4,2
Published 9 August 2023 • © 2023 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited
Journal of The Electrochemical Society, Volume 170, Number 8Citation Robert Marić et al 2023 J. Electrochem. Soc. 170 084505DOI 10.1149/1945-7111/aceb8d
Abstract
In fuel cell applications with long lifetime requirements, the management of stressing operating conditions—such as hydrogen starvation events—plays a pivotal role. Among other remedies, the incorporation of an OER-enhancing co-catalyst, is widely employed to improve the intrinsic stability of Pt/C-based anode catalyst layers in PEM fuel cells. The present study investigates several supported and unsupported Ir-based co-catalysts comprising different oxidation states of iridium: from metallic to oxidic character, both anhydrous rutile-type IrO2 and hydrated amorphous form. Utilizing a single-cell setup, cell reversal experiments were conducted initially after break-in of the MEA and after seven days of continuous operation under reductive H2 atmosphere at application-relevant conditions. The initial cell reversal tolerance was found to increase in the order metallic Ir < crystalline Ir oxide < amorphous Ir oxyhydroxide. By contrast, after continuous operation under H2 the order changes drastically to amorphous Ir oxyhydroxide ∼ metallic Ir < crystalline Ir oxide. This led us to conclude that the amorphous Ir oxyhydroxide is likely reduced to metallic Ir during continuous H2 operation, while IrO2 provides a reasonable trade-off between initial OER activity, high structural and chemical stability at high anode potentials during H2 starvation and low reducibility under prolonged H2 operation.
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