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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

Higgins, Drew, Wette, Melissa, Gibbons, Brenna M., Siahrostami, Samira, Hahn, Christopher, Escudero-Escribano, Mar?ia, Garcia-Melchor, Max, Ulissi, Zachary, Davis, Ryan C., Mehta, Apurva, Clemens, Bruce M., Norskov, Jens K., and Jaramillo, Thomas F.. Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes. United States: N. p., Web. doi:10.1021/acsaem.8b00090.
Higgins, Drew, Wette, Melissa, Gibbons, Brenna M., Siahrostami, Samira, Hahn, Christopher, Escudero-Escribano, Mar?ia, Garcia-Melchor, Max, Ulissi, Zachary, Davis, Ryan C., Mehta, Apurva, Clemens, Bruce M., Norskov, Jens K., & Jaramillo, Thomas F.. Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes. United States. doi:10.1021/acsaem.8b00090.
Higgins, Drew, Wette, Melissa, Gibbons, Brenna M., Siahrostami, Samira, Hahn, Christopher, Escudero-Escribano, Mar?ia, Garcia-Melchor, Max, Ulissi, Zachary, Davis, Ryan C., Mehta, Apurva, Clemens, Bruce M., Norskov, Jens K., and Jaramillo, Thomas F.. 2018. "Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes". United States. doi:10.1021/acsaem.8b00090.
@article{osti_1459655,
title = {Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes},
author = {Higgins, Drew and Wette, Melissa and Gibbons, Brenna M. and Siahrostami, Samira and Hahn, Christopher and Escudero-Escribano, Mar?ia and Garcia-Melchor, Max and Ulissi, Zachary and Davis, Ryan C. and Mehta, Apurva and Clemens, Bruce M. and Norskov, Jens K. and Jaramillo, Thomas F.},
abstractNote = {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 (Cu70Ag30) 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 miscibility of Cu atoms in the Ag-rich phase, which favourably tunes the surface electronic structure and binding energies of reaction species.},
doi = {10.1021/acsaem.8b00090},
journal = {ACS Applied Energy Materials},
number = 5,
volume = 1,
place = {United States},
year = {2018},
month = {5}
}