High-performance Ag–Co alloy catalysts for electrochemical oxygen reduction

An Erratum to this article was published on 22 September 2014

This article has been updated

Abstract

The electrochemical oxygen reduction reaction is the limiting half-reaction for low-temperature hydrogen fuel cells, and currently costly Pt-based electrocatalysts are used to generate adequate rates. Although most other metals are not stable in typical acid-mediated cells, alkaline environments permit the use of less costly electrodes, such as silver. Unfortunately, monometallic silver is not sufficiently active for economical fuel cells. Herein we demonstrate the design of low-cost Ag–Co surface alloy nanoparticle electrocatalysts for oxygen reduction. Their performance relative to that of Pt is potential dependent, but reaches over half the area-specific activity of Pt nanoparticle catalysts and is more than a fivefold improvement over pure silver nanoparticles at typical operating potentials. The Ag–Co electrocatalyst was initially identified with quantum chemical calculations and then synthesized using a novel technique that generates a surface alloy, despite bulk immiscibility of the constituent materials. Characterization studies support the hypothesis that the activity improvement comes from a ligand effect, in which cobalt atoms perturb surface silver sites.

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Figure 1: Pourbaix diagram for the oxidation of various metals.
Figure 2: DFT-calculated free-energy diagram for ORR on alloy catalyst surfaces.
Figure 3: Synthesis scheme and electrochemical oxygen-reduction performance of Ag–Co surface alloy materials.
Figure 4: Comparative CV of the Ag–Co surface alloy.
Figure 5: Electron microscopy and spectroscopy of Ag–Co materials.

Change history

  • 11 August 2014

    Technical issues with our online publication processes resulted in this Article being published the day after that referred to in the print version. The official date of publication is 11 August 2014.

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Acknowledgements

We acknowledge support from the US DOE Office of Basic Energy Sciences, Division of Chemical Sciences (FG-02-05ER15686). We also acknowledge the University of Michigan Electron Microbeam Analysis Laboratory for use of the microscopy facilities. This research is also supported as part of a user project by Oak Ridge National Laboratory (ORNL)'s Center for Nanophase Materials Sciences, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US DOE (J-C.I.). Finally, we acknowledge H. Xin and T. van Cleve for helpful discussions and experimental assistance.

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A.H. and S.L. devised and developed the project. A.H. carried out experimental work, theoretical calculations and data analysis. J-C.I. performed STEM and EELS imaging at ORNL. All the authors wrote the manuscript.

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Correspondence to Suljo Linic.

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Holewinski, A., Idrobo, JC. & Linic, S. High-performance Ag–Co alloy catalysts for electrochemical oxygen reduction. Nature Chem 6, 828–834 (2014). https://doi.org/10.1038/nchem.2032

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