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Title: Improved Oxygen Reduction Activity and Durability of Dealloyed PtCox Catalysts for Proton Exchange Membrane Fuel Cells: Strain, Ligand, and Particle Size Effects

The development of active and durable catalysts with reduced platinum content is essential for fuel cell commercialization. Here in this paper, we report that the dealloyed PtCo/HSC and PtCo3/HSC nanoparticle (NP) catalysts exhibit the same levels of enhancement in oxygen reduction activity (~4-fold) and durability over pure Pt/C NPs. Surprisingly, ex situ high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) shows that the bulk morphologies of the two catalysts are distinctly different: D-PtCo/HSC catalyst is dominated by NPs with solid Pt shells surrounding a single ordered PtCo core; however, the D-PtCo3/HSC catalyst is dominated by NPs with porous Pt shells surrounding multiple disordered PtCo cores with local concentration of Co. In situ X-ray absorption spectroscopy (XAS) reveals that these two catalysts possess similar Pt–Pt and Pt–Co bond distances and Pt coordination numbers (CNs), despite their dissimilar morphologies. The similar activity of the two catalysts is thus ascribed to their comparable strain, ligand, and particle size effects. Ex situ XAS performed on D-PtCo3/HSC under different voltage cycling stage shows that the continuous dissolution of Co leaves behind the NPs with a Pt-like structure after 30k cycles. The attenuated strain and/or ligand effects caused by Co dissolution are presumably counterbalancedmore » by the particle size effects with particle growth, which likely accounts for the constant specific activity of the catalysts along with voltage cycling.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [2] ;  [1]
  1. Northeastern Univ., Boston, MA (United States). Dept. of Chemistry and Chemical Biology
  2. George Washington Univ., Washington, DC (United States). Dept. of Chemistry
  3. General Motors Central Research and Development, Warren, MI (United States). Electrochemical Energy Research Lab.
Publication Date:
OSTI Identifier:
1165320
Grant/Contract Number:
EE0000458; AC02-98CH10886; P30-EB-009998
Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 5; Journal Issue: 1; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Program (EE-3F); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; in situ XAS; ligand effects; ORR; particle size effects; Pt-based nanocatalysts; strain effects