Enhancement of alkaline water-oxidation activity for amorphous CoOx by the underlying remote-region atom seeding

Abstract

Scaling up hydrogen production via large-current-density water electrolysis requires durable electrocatalysts of oxygen evolution reaction (OER) to reduce energy consumption. While amorphous metal oxides are promising OER catalysts, the surface-sites-electronic-orbital chance from the underlying remote-region atom seeding remains elusive. Herein, vanadium atom was controllable seated in the underlying remote region of the bulk materials as a typical coupling mode of amorphous-CoVOx-supported amorphous CoOx (CoVOx@CoOx), to study long-distance atoms correlation. XPS characterization for CoVOx@CoOx can't reveal the V signal due to the limited test depth of 5 nm, suggesting that V is existent in the internal region where it can be detected by EDS with 1 μm test depth. For surface-etched CoVOx@CoOx, V XPS signal appeared due to the exposure of CoVOx counterpart. The bionic flower structured, amorphous CoVOx@CoOx presents low overpotential of 338.5 mV at an extremely high current density of 1000 mA cm−2 in 1 M KOH and reserves 90.4% of the initial catalytical current after 24 h operation, significantly outperforming single amorphous CoOx. Density functional theory calculations evidence that the charge transfer from V atoms of CoVOx to surface active Co sites of CoOx part leads to the d-band center of Co-3d orbital shifted towards the Fermi level, which enhanced O adsorption effect thus promoting the OER activity. This research not only provides an ultrahigh-current-tolerance OER catalyst but also throws in-depth insight into the long-distance atoms charge interaction towards knowledge-guide catalyst construction for practical utilization.