Understanding the Electrochemical Dissolution of IrO2 PEM Electrolyzer Anode Catalyst Using Online ICP-MS

Abstract

The transition to a sustainable society largely relies upon the utilization of renewable energy sources such as solar and wind power.1,2 However, due to their intermittent availability, energy storage and conversion systems such as electrolyzers and fuel cells have become a crucial topic of research and development. Electrocatalysis efforts in low temperature, PEM-based electrolysis tend to focus on the oxygen evolution reaction (OER) since it is several orders of magnitude kinetically slower than its counterpart, the hydrogen evolution reaction (HER). 3 In comparison to other OER catalysts, Ir-based metal oxides (IrOx)4-8 are regarded as the best PEM electrolyzer electrocatalysts as they are both active and, compared to alternatives, such as RE-based oxides, are relatively stable.9,10 However, even Ir-based electrocatalysts slowly undergo dissolution under the operating conditions of the electrolyzer anode. 11-12, 9 Considering the non-renewable and high-cost of Ir, understanding the kinetics and mechanism of its electrochemical dissolution is of vital importance to develop strategies targeting high activity, long-term stability, and limited metal dissolution in acidic media. Mechanistic studies of both OER and dissolution at the solid–liquid interface are more challenging, as they typically require detection of reaction intermediates with short lifetimes. A number of studies have shown possible routes for OER-activated Ir dissolution involve participartion of IrIII, IrIV, and IrV species.13 An electrochemical cell coupled to a highly sensitive analytical technique provides a platform for detection of reaction intermediates and may help to resolve the degradation pathway of Ir and its oxides and the correlation to the OER mechanism.This presentation will outline the dissolution of iridium oxide (IrO2) under various operating conditions. Studies are performed to quantify the amount of dissolved Ir during potentiodynamic conditions in an electrochemical flow cell system connected to an inductively-coupled plasma-mass spectrometer (ICP-MS) capable of detecting trace concentrations (<ppb) of dissolved elements in solution. The electrochemical data combined with the ICP-MS data are used to evaluate the influence of various factors such as potential, potentiodynamic profile parameters (e.g., scan rate, upper and lower potential limits) and catalyst type, on the dissolution processes in acidic electrolytes at room temperature. Fundamental models will be developed to explain the mechanisms of dissolution process under various potential conditions. Acknowledgements This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the H2NEW Consortium. This work was authored in part by Argonne National Laboratory, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357. References N. S. Lewis, D. G. Nocera, Proc. Natl. Acad. Sci., 103, 15729 (2006).V. R. Stamenkovic, D. Strmcnik, P. P. Lopes, N. M. Markovic, Nat. Mater., 16, 57 (2017).S. M. Alia, B. Rasimick, C. Ngo, K. C. Neyerlin, S. S. Kocha, S. Pylypenko, H. Xu, B. S. Pivovar, J. Electrochem. Soc., 163, F3105 (2016).S. M. Alia, M. -A. Ha, G. C. Anderson, C. Ngo, S. Pylypenko, R. E. Larsen, J. Electrochem. Soc., 166, F1243 (2019).S. Cherevko, S. Geiger, O. Kasian, N. Kulyk, J. P. Grote, A. Savan, B. R. Shrestha, S. Merzlikin, B. Breitbach, A. Ludwig, et al., Catal. Today, 262, 170 (2016).Y. Lee, J. Suntivich, K. J. May, E. E. Perry, Y. Shao-Horn, J. Phys. Chem. Lett., 3, 399 (2012).D. F. Abbott, D. Lebedev, K. Waltar, M. Povia, M. Nachtegaal, E. Fabbri, C. Copéret, T. J. Schmidt, Chem. Mater., 28, 6591 (2016).H. N. Nong, T. Reier, H.-S. Oh, M. Gliech, P. Paciok, T. H. T. Vu, D. Teschner, M. Heggen, V. Petkov, R. Schlögl, et al., Nat. Catal. , 1, 841(2018).N. Danilovic, R. Subbaraman, K.-C. Chang, S. H. Chang, Y. J. Kang, J. Snyder, A. P. Paulikas, D. Strmcnik, Y.-T. Kim, and D. Myers, J. Phys.Chem. Lett., 5, 2474 (2014).T. Reier, M. Oezaslan, and P. Strasser, ACS Catalysis, 2, 1765 (2012).S. Cherevko, S. Geiger, O. Kasian, N. Kulyk, J.-P. Grote, A. Savan, B. R. Shrestha, S. Merzlikin, B. Breitbach, A. Ludwig, K. J. J. Mayrhofer, Catal. Today, 262, 170 (2016).O. Kasian, S. Geiger, P. Stock, G. Polymeros, B. Breitbach, A. Savan, A. Ludwig, S. Cherevko, K. J. J. Mayrhofer, J. Electrochem. Soc., 163, F3099 (2016).O. Kasian, J.-P. Grote, S. Geiger, S. Cherevko, and K.J.J. Mayrhofer, Angew. Chem. Int. Ed. , 57, 2488 (2018).