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Published January 2019 | Published + Supplemental Material
Journal Article Open

Hydrogen oxidation kinetics on platinum-palladium bimetallic thin films for solid acid fuel cells

Abstract

Solid acid fuel cells (SAFCs) based on the proton-conductive electrolyte CsH2PO4 have shown promising power densities at an intermediate operating temperature of ∼250 °C. However, Pt loadings in SAFCs remain higher than desirable, and the electrocatalysis mechanisms in these devices are still unknown. Here, hydrogen oxidation kinetics on Pt and Pt-Pd bimetallic thin film electrodes on CsH2PO4 have been evaluated to establish the potential for a beneficial role of Pd in SAFC anodes. Symmetric cells fabricated by depositing a metal film on both sides of electrolyte discs are characterized for studying hydrogen electro-oxidation across the gas|metal|CsH2PO4 structure. It was found that Pd reacts with CsH2PO4, forming palladium phosphide at the metal-electrolyte interface. Accordingly, the activity of Pd was examined in a bilayer geometry of Pd|Pt|CsH2PO4|Pt|Pd. The bilayer Pt|Pd films showed much higher activity for hydrogen electro-oxidation than films of Pt alone, as measured by AC impedance spectroscopy. Ex situ low energy ion scattering and scanning transmission electron microscopy revealed that Pd diffused into the Pt layer under operating conditions. The dramatic impact of Pd along with its presence throughout the film suggests that it catalyzes reactions at both the metal-gas and metal-electrolyte interfaces, as well as increasing hydrogen diffusion rates through the films.

Additional Information

© Author(s) 2018. All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Submitted: 27 July 2018 • Accepted: 2 September 2018 • Published Online: 6 December 2018. This research was supported by the Kwanjeong Educational Foundation and the U.S. Department of Energy, through ARPA-e Contract Nos. DE-AR0000495 and DE-AR0000813. This work utilized Micro/Nano Fabrication Facility (NUFAB), NUANCE Center (EPIC and Keck-II), and J. B. Cohen Diffraction X-ray Diffraction Facility at Northwestern University, which are all supported by the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (No. NSF ECCS-1542205) and MRSEC program of the National Science Foundation (No. DMR-1720139) at the Materials Research Center. We thank Xin Xu and Kaiting Li for assistance with sample preparation.

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Created:
August 19, 2023
Modified:
October 19, 2023