Oxygen reduction is one of the most ubiquitous electrochemical reactions. It controls respiration in nature, corrosion of metals and defines the efficiency of low temperature fuel cells and metal-air batteries for renewable energy conversion.
Earlier theoretical and experimental works showed that the binding to the reaction intermediates controls oxygen reduction in acid media: on metal surfaces, the most active catalyst should exhibit an OH binding 0.1 eV weaker than Pt(111) single crystal, via a Sabatier volcano.1,2 This knowledge has enabled the huge decreases in the amount of platinum required to catalyse oxygen reduction in state-of-the-art fuel cells.3,4
Aqueous metal air batteries and alkaline membrane fuel cells employ basic electrolytes. However, in contrast to acid, there is no consensus in the literature on the factors controlling oxygen reduction at high pH.5,6 In the current contribution, we directly address the controversies in the literature. I will describe how we experimentally elucidated the factors controlling oxygen reduction on metal surfaces using a platinum-alloy single crystal.7 We combine electrochemical measurements with X-ray photoelectron spectroscopy and density functional theory calculations. It turns out that OH binding also controls the trends in catalytic activity at high pH. As such, our work provides the key design principle for the reaction in basic media.
References
1 Nørskov, J. K., Rossmeisl, J., Logadottir, A., Lindqvist, L., Kitchin, J. R., Bligaard, T. & Jonsson, H. Journal of Physical Chemistry B 108, 17886, (2004).
2 Stephens, I. E. L., Bondarenko, A. S., Perez-Alonso, F. J., Calle-Vallejo, F., Bech, L., Johansson, T. P., Jepsen, A. K., Frydendal, R., Knudsen, B. P., Rossmeisl, J. & Chorkendorff, I. J. Am. Chem. Soc. 133, 5485, (2011).
3 Han, B. H., Carlton, C. E., Kongkanand, A., Kukreja, R. S., Theobald, B. R., Gan, L., O’Malley, R., Strasser, P., Wagner, F. T. & Shao-Horn, Y. Energy Environ. Sci. 8, 258, (2015).
4 Stephens, I. E. L., Rossmeisl, J. & Chorkendorff, I. Science 354, 1378, (2016).
5 Quaino, P., Luque, N. B., Nazmutdinov, R., Santos, E. & Schmickler, W. Angewandte Chemie International Edition 51, 12997, (2012).
6 Staszak-Jirkovský, J., Subbaraman, R., Strmcnik, D., Harrison, K. L., Diesendruck, C. E., Assary, R., Frank, O., Kobr, L., Wiberg, G. K. H., Genorio, B., Connell, J. G., Lopes, P. P., Stamenkovic, V. R., Curtiss, L., Moore, J. S., Zavadil, K. R. & Markovic, N. M. ACS Catalysis 5, 6600, (2015).
7 Jensen, K. D., Tymoczko, J., Rossmeisl, J., Bandarenka, A. S., Chorkendorff, I., Escudero-Escribano, M. & Stephens, I. E. L. Angewandte Chemie International Edition 57, 2800, (2018).