Dealloyed Pt74Ni26 and Pt26Ni74 Electrodeposited Thin Film Electrocatalysts for Oxygen Reduction

Published

May 30, 2024

Author(s)

Carlos Hangarter, Eric Rus, Yihua Liu, Jaw Wook Shin, Vladimir Oleshko, Hyun Wook Ro, Russell Composto, Christopher Soles, Joseph A. Dura, Gery R. Stafford, Leonid Bendersky, Thomas P. Moffat

Abstract

Pt100-xNix alloys are among the most active binary alloys for electrocatalysis of the oxygen reduction reaction (ORR) in PEM fuel cells. Electrodeposition and microstructure of thin films close to Pt75Ni25 and Pt25Ni75 stoichiometry are described and their catalytic ORR performance, dealloying, and strain evolution are detailed. Multiple techniques are used to characterize the morphology, crystalline structure, and chemical homogeneity of the as-deposited and dealloyed films at various length scales. A fine-scale percolating network of lower-density regions is evident in the as-deposited Pt74Ni26 films while the as-deposited Pt26Ni74 films are more homogenous and compact. Electrodeposition is accompanied by the development of significant in-plane tensile stress that increases at more negative applied growth potentials to reach 1.28 GPa for as-deposited Pt26Ni74. Dealloying of the near-surface regions of Pt74Ni26 is accompanied by limited expansion or opening of the low-density regions while massive dealloying of the highly stressed Pt26Ni74 results in shrinkage, extensive cracking, and formation of a bi-continuous nanoporous structure with an average pore diameter close to 5 nm. Evolution of the electroactive area is tracked by using hydrogen underpotential deposition (Hupd) to monitor Pt surface sites and using the Ni(OH)2/NiOOH reaction, measured during periodic transfers to alkaline solution, to assay Ni sites. Relative to electrodeposited Pt, the alloy films exhibit enhanced area-specific oxygen reduction reaction activity (at 0.95 V vs. RHE, iR-corrected) that amounts to a factor of 3.4 for dealloyed Pt74Ni26 and 5.1 for dealloyed Pt26Ni74 while the Pt-based mass activity increased by a factor of 5.1 and 12.3, for the respective films.

Citation

ACS Catalysis

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Journals

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Keywords

platinum nickel, electrocatalysis, oxygen reduction reaction, porosity, x-ray diffraction, x-ray reflectometry, Rutherford backscattering spectroscopy, bimetallic alloy, stress corrosion cracking

Citation

Hangarter, C. , Rus, E. , Liu, Y. , Shin, J. , Oleshko, V. , Ro, H. , Composto, R. , Soles, C. , Dura, J. , Stafford, G. , Bendersky, L. and Moffat, T. (2024), Dealloyed Pt74Ni26 and Pt26Ni74 Electrodeposited Thin Film Electrocatalysts for Oxygen Reduction, ACS Catalysis, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957273 (Accessed November 21, 2024)