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

Journal Article · 05 December 2018 · APL Materials

DOI: https://doi.org/10.1063/1.5050093 · OSTI ID:1613623

Paik, Haemin ^[1]; Berenov, Andrey V. ^[2]; Skinner, Stephen J.  ^[2]; Haile, Sossina M. ^[3]

---

1. California Institute of Technology (CalTech), Pasadena, CA (United States); DOE/OSTI
2. Imperial College, London (United Kingdom)
3. California Institute of Technology (CalTech), Pasadena, CA (United States); Northwestern Univ., Evanston, IL (United States)

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.

• Research Organization: SAFCell, Inc., Pasadena, CA (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• Grant/Contract Number: AR0000495; AR0000813
• OSTI ID: 1613623
• Journal Information: APL Materials, Journal Name: APL Materials Journal Issue: 1 Vol. 7; ISSN 2166-532X
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English