Ultra-stable and poison tolerant oxygen evolution activity enabled by surface In2O3−x(OH)y of Co3In2S2 large single crystals†

Abstract

Water is an earth-abundant source for clean hydrogen production via electrochemical water electrolysis (WE). However, the surface poisoning that occurs in aqueous electrolytes drastically deactivates the electrocatalytic performance of electrodes. Here, we report electrochemically formed In₂O_3−x(OH)_y on the surface of a large (1–1.5 mm long, 0.5–0.6 mm wide and 0.3–0.5 mm thick) single crystal of Weyl semimetal Co₃In₂S₂ (Co₃In₂S₂/In₂O_3−x(OH)_y) as an ultra-stable and poison tolerant electrode for the oxygen evolution reaction (OER) in 1 M KOH, addressing a bottleneck in WE. The OER activity of the powder form of Co₃In₂S₂ is limited by its aerophilic nature. Remarkably, the single-crystal electrodes maintained their high activity for a continuous operational period of 5 h in 1 M KOH electrolyte with/without 10 mM strong surface-poisoning ligands i.e., potassium cyanide, bipyridine, and ethylenediaminetetraacetate disodium salt. The electrodes exhibited stable OER activity for 1000 h at 100 mA cm⁻² (1.73 V vs. RHE). The temperature-dependent OER polarization curves (10–70 °C) unambiguously revealed surface poisoning through the suppression of precatalytic Co-redox peaks on the bipyridine poisoned electrode, which led to the stabilization of surface Co-sites. The X-ray photoelectron spectroscopy analyses of pristine, poisoned and post-electrocatalytic single-crystal Co₃In₂S₂ electrodes revealed the existence of an In₂O_3−x(OH)_y surface phase, which could be the potential heterostructure for the origin of ultra-stable and poison tolerant OER activity.