PNNL

Abstract

Water is an earth-abundant source for clean hydrogen production via electrochemical water electrolysis. However, the surface poisoning that occurs in aqueous electrolytes deactivates the electrocatalytic performance of electrodes. Here, we report on a novel electrochemically formed In2O3-x(OH)y surface layer on a single-crystal of Weyl semimetal Co3In2S2 (Co3In2S2/In2O3-x(OH)y) as a substrate-free and ink-free electrode for the oxygen evolution reaction (OER) in an alkaline environment, addressing a bottleneck in efficient water electrolysis. The single-crystal electrode exhibited ultra-stable OER activity for 1000 h at 100 mA cm-2 (1.73 V vs. RHE). Remarkably, the electrodes maintained their activity for a continuous operational period of 5 h in 1 M KOH electrolyte containing 10 mM of strong surface-poisoning ligands i.e., potassium cyanide, bipyridine, and ethylenediaminetetraacetate disodium salt. The temperature-dependent OER polarization curves (10–70 °C) unambiguously revealed surface poisoning through the suppression of precatalytic Co-redox peaks in the presence of bipyridine ligand. The electrochemical performance, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy analyses of single-crystal Co3In2S2 electrodes revealed the existence of a In2O3-x(OH)y surface layer that is ultra-stable and has a poison tolerance in the OER activity. A.W. acknowledges the financial support from the National Science Foundation Ceramics Program under DMR-1929306). C.M. and J.-S.M. acknowledge the financial support from the National Science Foundation CAREER program under CBET- 1653561. This work was partially funded by the Joint Center for Deployment and Research in Earth Abundant Materials (JCDREAM) in Washington State. We also thank Dr. Dezhou Guo for the fruitful DFT discussions. Computational resources were provided by the Kamiak HPC under the Center for Institutional Research Computing at Washington State University. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. DOE.