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

Drew Higgins; Melissa Wette; Brenna M. Gibbons; Samira Siahrostami; Christopher Hahn; Marı́a Escudero-Escribano; Max García-Melchor; Zachary Ulissi; Ryan C. Davis; Apurva Mehta; Bruce M. Clemens; Jens K. Nørskov; Thomas F. Jaramillo

doi:10.1021/acsaem.8b00090

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

Drew Higgins, Melissa Wette, Brenna M. Gibbons, Samira Siahrostami, Christopher Hahn, Marı́a Escudero-Escribano, Max García-Melchor, Zachary Ulissi, Ryan C. Davis, Apurva Mehta, Bruce M. Clemens, Jens K. Nørskov, Thomas F. Jaramillo

Department of Chemistry

17 Citations (Scopus)

Abstract

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 electron beam physical vapor 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 vs pure Ag at 0.8 V vs the reversible hydrogen electrode. Furthermore, enhanced ORR kinetics for Cu-rich (>50 at. % 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. 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 favorably tunes the surface electronic structure and binding energies of reaction species.

Original language	English
Journal	ACS Applied Energy Materials
Volume	1
Issue number	5
Pages (from-to)	1990-1999
Number of pages	10
ISSN	2574-0962
DOIs	https://doi.org/10.1021/acsaem.8b00090
Publication status	Published - 29 May 2018

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Higgins, D., Wette, M., Gibbons, B. M., Siahrostami, S., Hahn, C., Escudero-Escribano, M., García-Melchor, M., Ulissi, Z., Davis, R. C., Mehta, A., Clemens, B. M., Nørskov, J. K., & Jaramillo, T. F. (2018). Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes. ACS Applied Energy Materials, 1(5), 1990-1999. https://doi.org/10.1021/acsaem.8b00090

Higgins, D, Wette, M, Gibbons, BM, Siahrostami, S, Hahn, C, Escudero-Escribano, M, García-Melchor, M, Ulissi, Z, Davis, RC, Mehta, A, Clemens, BM, Nørskov, JK & Jaramillo, TF 2018, 'Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes', ACS Applied Energy Materials, vol. 1, no. 5, pp. 1990-1999. https://doi.org/10.1021/acsaem.8b00090

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title = "Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes",

abstract = "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 electron beam physical vapor 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 vs pure Ag at 0.8 V vs the reversible hydrogen electrode. Furthermore, enhanced ORR kinetics for Cu-rich (>50 at. % 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. 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 favorably tunes the surface electronic structure and binding energies of reaction species.",

author = "Drew Higgins and Melissa Wette and Gibbons, {Brenna M.} and Samira Siahrostami and Christopher Hahn and Mar{\'ı}a Escudero-Escribano and Max Garc{\'i}a-Melchor and Zachary Ulissi and Davis, {Ryan C.} and Apurva Mehta and Clemens, {Bruce M.} and N{\o}rskov, {Jens K.} and Jaramillo, {Thomas F.}",

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T1 - Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes

AU - Higgins, Drew

AU - Wette, Melissa

AU - Gibbons, Brenna M.

AU - Siahrostami, Samira

AU - Hahn, Christopher

AU - Escudero-Escribano, Marı́a

AU - García-Melchor, Max

AU - Ulissi, Zachary

AU - Davis, Ryan C.

AU - Mehta, Apurva

AU - Clemens, Bruce M.

AU - Nørskov, Jens K.

AU - Jaramillo, Thomas F.

PY - 2018/5/29

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N2 - 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 electron beam physical vapor 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 vs pure Ag at 0.8 V vs the reversible hydrogen electrode. Furthermore, enhanced ORR kinetics for Cu-rich (>50 at. % 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. 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 favorably tunes the surface electronic structure and binding energies of reaction species.

AB - 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 electron beam physical vapor 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 vs pure Ag at 0.8 V vs the reversible hydrogen electrode. Furthermore, enhanced ORR kinetics for Cu-rich (>50 at. % 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. 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 favorably tunes the surface electronic structure and binding energies of reaction species.

U2 - 10.1021/acsaem.8b00090

DO - 10.1021/acsaem.8b00090

M3 - Journal article

SN - 2574-0962

VL - 1

SP - 1990

EP - 1999

JO - ACS Applied Energy Materials

JF - ACS Applied Energy Materials

IS - 5

ER -

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

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