Metal–Air Electrochemical Cells: Silver–Polymer–Carbon Composite Air Electrodes

Abstract

Reported herein is the study of the preparation, characterization, and electrochemical activity of a silver-polymer-carbon composite electrode in a nonaqueous cell. An enhanced oxygen reduction activity for the composite electrode in a nonaqueous, aprotic solvent is demonstrated, relative to uncoated glassy carbon or silver disk electrodes. The improvement of oxygen reduction activity increases the current capability and power output of the air electrode, facilitating future development of small, lightweight, long-life power sources.Metal-air batteries are unusual because the electroactive cathode material ͑O 2 ͒ is provided by ambient air, so the only electroactive material contained within metal-air batteries is the anode. Although aqueous metal-air batteries have been successfully deployed in consumer-as well as defense-related applications, 1 the development of practical nonaqueous metal-air batteries 2 remains a challenge. The investigation of nonaqueous metal-air batteries is receiving increased attention as a research focus area, with several recent studies focusing on various aspects of electrolyte formulation, 3-6 cathode, 7 and air battery design. 8,9 The search for new materials to promote oxygen reduction has been an area of research interest. 10 The primary focus to date has been metal oxides. 3,[11][12][13] This article is the first study of the electrochemical reduction of O 2 at a silver-polymer-carbon electrode in a nonaqueous cell. The preparation, characterization, and electrochemical activity of a novel composite electrode containing silver on a polypyrrole ͑PPy͒-coated carbon substrate are described here. An enhanced oxygen reduction activity for the composite electrode is observed relative to uncoated glassy carbon ͑GC͒ or silver disk electrodes. The improvement of the cathode oxygen reduction activity increases the current capability and power output of the air electrode, facilitating future development of small, lightweight, long-life power sources. ExperimentalCH Instruments potentiostats and electrodes were used for the deposition, oxygen reduction, and ac impedance experiments. Platinum auxiliary electrodes were used for all experiments. Reference electrodes were purchased from CH Instruments. For aqueous measurements, a silver/silver chloride reference was used, whereas for nonaqueous measurements, a silver/silver nitrate reference electrode was used. All potentials reported are relative to the reference electrodes used. A Thermo Fisher Scientific ICAP 6000 inductively coupled plasma spectrophotometer was used for silver analysis. Scanning electron microscopy ͑SEM͒ images were recorded using a Hitachi S-800.Temperature was maintained at 25°C throughout all electrochemical experiments. Silver deposition was conducted in a method consistent with that described by Palomar-Pardavé and co-workers. 14 PPy was deposited using a methodology similar to that described by Wallace, Ralph, and co-workers. 15,16 Oxygen reduction was measured using an electrolyte of 0.1 M tetrabutylammonium hexafluor...

Progress toward Metal-Air Batteries: Mechanistic Investigation of the Effect of Water on the Oxygen Reduction Reaction at Carbon-Conductive Polymer-Silver Composite Air Electrodes

“…9 Enhanced oxygen reduction activity for our composite electrode was observed relative to coated glassy carbon or silver disk electrodes, at a low silver loading of < 0.3 mg cm −2 . Specifically, the role of the current collector toward the electrochemical reduction of oxygen, the role of the conductive polymer in improving the structural integrity of the composite electrode, and a quantitative study of the silver loading effect on ORR activity were all investigated.…”

“…22,23 Oxygen reduction was measured using an electrolyte of 0.1 M tetrabutylammonium tetrafluoroborate (TBABF 4 ) in acetonitrile (MeCN), at potential sweep rates of 50, 100, 180, 225, 325 and 500 mV s −1 . CH Instruments potentiostats were used for the deposition, oxygen reduction experiments.…”

“…Glassy Carbon-Polypyrrole (C-cp) electrode.-Glassy carbon electrodes were coated with polypyrrole following a previously reported procedure to form carbon-conductive polymer (C-cp) composite electrodes. 22 The estimated thicknesses of the polypyrrole coatings were ∼4-7 microns. Under these deposition conditions, the polypyrrole forms a conformal layer which completely masks the electrochemistry of the underlying substrate during ORR.…”

Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

“…8), 34 and showing comparable activity to a gold (Au) disk electrode. 35 AC impedance measurements taken to assess the conductivity of the C-cp-Ag composite electrode near open circuit potential and at an appropriate potential for oxygen reduction verified that the composite electrode maintained its conductivity at a negative potential appropriate for oxygen reduction.…”

Oxygen Reduction Activity of Carbon-Conductive Polymer-Silver Composite Electrodes

“…The C-Cp-Ag composite preparation procedure has been previously described (6)(7). Carbon-conductive polymer-silver (C-cp-Ag) composite electrodes were prepared using successive electrodeposition processes ( Figure 1).…”