(Invited) Development of High Performance Non-PGM Electrocatalysts and Electrodes for the Oxygen Reduction Reaction in Aemfcs

Abstract

Anion exchange membrane fuel cells (AEMFCs) have received significant attention in recent years as a potentially lower cost electrochemical energy conversion device compared to proton exchange membrane fuel cells (PEMFCs) [1]. In the past few years, several achievements have been made in terms of single cell performance, including power densities comparable to PEMFCs (~ 1.9 W cm-2)[2–4], and stability over hundreds of hours of operation[5,4], which are critical to the development and future deployment of AEMFCs. However, to make AEMFCs more economically competitive, or even favorable, with PEMFCs, it is crucial to discover non-PGM electrocatalysts for both the oxygen reduction reaction (ORR) and hydrogen oxidation reaction in AEMFCs that are able to achieve high power densities and long term operation. Over the last decade, significant progress has been made in finding PGM-free catalysts for the ORR in alkaline media. However, an overwhelming majority of the tests with these materials have been done ex-situ using rotating disk electrodes (RDE), and these measurements and are not typically representative of the in-cell performance due to more complicated mass transport and reacting conditions. Hence, many highly active ex-situ catalysts have shown limited performance in operating AEMFCs. In this work, we studied two types of non-PGM electrocatalysts, including CoOx embedded in nitrogen-doped carbon (CoOx-N-C)[6] and classical Fe-N-C, for the ORR in AEMFCs. Not only was the ORR activity fully characterized using RDE and RRDE measurements, with both catalyst exhibiting excellent half-cell activity, but they were also incorporated into gas diffusion electrodes and studied in 5 cm-2 single cell AEMFCs. This study was able to show that PGM-free electrodes are able to support high performance (> 1.0 W cm-2), achievable current density and stability (>100 h). This work demonstrates a significant improvement in non-PGM electrocatalysts development and performance than previous work. Reference: [1] J. R. Varcoe, P. Atanassov, D. R. Dekel, A. M. Herring, M. A. Hickner, P. A. Kohl, A. R. Kucernak, W. E. Mustain, K. Nijmeijer, K. Scott, et al., Energy Environ. Sci. 2014, 7, 3135–3191. [2] L. Wang, E. Magliocca, E. L. Cunningham, W. E. Mustain, S. D. Poynton, R. Escudero-Cid, M. M. Nasef, J. Ponce-González, R. Bance-Souahli, R. C. T. Slade, et al., Green Chem. 2017, 19, 831–843. [3] T. J. Omasta, L. Wang, X. Peng, C. A. Lewis, J. R. Varcoe, W. E. Mustain, J. Power Sources 2018, 375, 205–213. [4] T. J. Omasta, A. M. Park, J. M. LaManna, Y. Zhang, X. Peng, L. Wang, D. L. Jacobson, J. R. Varcoe, D. S. Hussey, B. S. Pivovar, et al., Energy Environ. Sci. 2018, 11, 551–558. [5] W. E. Mustain, Curr. Opin. Electrochem. 2018, 1–7. [6] xiong peng, T. J. Omasta, E. Magliocca, L. Wang, J. R. Varcoe, W. E. Mustain, Angew. Chemie Int. Ed. 2018, 1–7.