Abstract
Stress tests are developed for proton exchange membrane electrolyzers that utilize low catalyst loading, elevated potential, and frequent cycling with square- and triangle-waves to accelerate anode catalyst layer degradation during intermittent operation. Kinetics drive performance losses (ohmic/transport secondary) and are accompanied by decreasing exchange current density, decreasing cyclic voltammetric capacitance, and increasing polarization resistance. Decreased kinetics are likely due to a combination of iridium (Ir) migration into electrochemically inaccessible locations in the anode or membrane, Ir particle growth (supported by X-ray scattering), changes in the extent of the Ir oxidation state (supported by X-ray absorption spectroscopy), and anode catalyst layer reordering. Decreasing catalyst/transport layer contact and catalyst/membrane interfacial tearing may add contact resistances and account for increasing ohmic losses. Performance losses for low and moderate catalyst loading, as well as from accelerated and model wind/solar cycling protocols, were likewise dominated by kinetics but vary in severity. Accelerated cycling (1 cycle per minute) appears to reasonably accelerate relevant loss mechanisms and can be used to project electrolyzer lifetime from anode deterioration. Ongoing accelerated stress test development and studies into performance loss mechanisms will continue to be critical as electrolysis shifts to intermittent power and low-cost applications.
| Original language | English |
|---|---|
| Article number | 054517 |
| Journal | Journal of the Electrochemical Society |
| Volume | 169 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 1 2022 |
Funding
This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. The work was also authored in part by Argonne National Laboratory, operated by UChicago Argonne for the U.S. Department of Energy, Office of Science, under Contract No. DEAC02-06CH11357. Funding was provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office through H2@Scale (NREL) and the H2NEW Consortium (ORNL, ANL). Electron microscopy was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The FEI Talos F200X S/TEM instrument provided by US DOE, Office of Nuclear Energy, Fuel Cycle Research and Development and the Nuclear Science User Facilities. The X-ray absorption experiments were performed at the Advanced Photon Source (APS), a DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357. The operation of MRCAT at the APS is supported by the Department of Energy and the MRCAT member institutions. The authors would like to thank Jan Ilavsky and Ivan Kuzmenko of the APS 9-ID-C (MRCAT, 10-BM and 10-ID) and scattering (XSD, 9-ID-C). The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.