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This content will become publicly available on May 7, 2019

Title: Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes

Increasing the activity of Ag-based catalysts for the oxygen reduction reaction (ORR) is important for improving the performance and economic outlook of alkaline-based fuel cell and metal-air battery technologies. In this work, we prepare CuAg thin films with controllable compositions using e-beam physical vapour deposition. X-ray diffraction analysis indicates that this fabrication route yields metastable miscibility between these two thermodynamically immiscible metals, with the thin films consisting of a Ag-rich and a Cu-rich phase. Electrochemical testing in 0.1 M potassium hydroxide showed significant ORR activity improvements for the CuAg films. On a geometric basis, the most active thin film (Cu 70Ag 30) demonstrated a 4-fold activity improvement versus pure Ag at 0.8 V vs the reversible hydrogen electrode. Furthermore, enhanced ORR kinetics for Cu-rich (> 50at % Cu) thin films was demonstrated by a decrease in Tafel slope from 90 mV/dec, a commonly observed value for Ag catalysts, to 45 mV/dec. Surface enrichment of the Ag-rich phase after ORR testing was indicated by x-ray photoelectron spectroscopy and grazing incidence synchrotron x-ray diffraction measurements. Here, by correlating density functional theory with experimental measurements, we postulate that the activity enhancement of the Cu-rich CuAg thin films arises due to the non-equilibrium miscibilitymore » of Cu atoms in the Ag-rich phase, which favourably tunes the surface electronic structure and binding energies of reaction species.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [1] ; ORCiD logo [1] ;  [4] ;  [5] ;  [1] ;  [6] ; ORCiD logo [6] ;  [2] ;  [1] ; ORCiD logo [1]
  1. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Stanford Univ., Stanford, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
  4. Stanford Univ., Stanford, CA (United States); Univ. of Copenhagen, Copenhagen (Denmark)
  5. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Trinity College Dublin, Dublin (Ireland)
  6. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Grant/Contract Number:
SC0008685; AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
ACS Applied Energy Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 5; Journal ID: ISSN 2574-0962
Publisher:
American Chemical Society (ACS)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; chloroalkali process; electrocatalysis; electrochemistry; fuel cells; oxygen reduction; physical vapor deposition; sustainable energy; thin films
OSTI Identifier:
1459655