Elsevier

Journal of Catalysis

Volume 412, August 2022, Pages 78-86
Journal of Catalysis

Metal coordination determines the catalytic activity of IrO2 nanoparticles for the oxygen evolution reaction

https://doi.org/10.1016/j.jcat.2022.05.023Get rights and content
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Highlights

  • • Structure-activity relationships for the IrO2 Wulff-like nanoparticles sites.

  • • Low coordinated iridium sites are oxidized to Ir(O)(OH)X at reaction potentials.

  • • Nanoparticle face sites behave similarly to main crystalline surface species.

  • • Low coordinated iridium centers at corners and edges show lower overpotentials.

  • • The OER activity depends on the metal coordination and vacant site nature.

Abstract

H2 production through water electrolysis is a promising strategy for storing sunlight energy. For the oxygen evolution reaction, iridium oxide containing materials are state-of-the-art due to their stability in acidic conditions. Moreover, precious metal content can be reduced by using small nanoparticles that show high catalytic activities. We performed DFT calculations on a 1.2 nm large IrO2 Wulff-like stoichiometric nanoparticle model (IrO2) with the aim of determining the factors controlling the catalytic activity of IrO2 nanoparticles. Results show that at reaction conditions tetra- and tricoordinated iridium centers are not fully oxidized, the major species being IrO(OH) and IrO(OH)2, respectively. Although the computed overpotential show that all centers present relatively similar reactivities, low coordinated iridium centers tend to be more active than the pentacoordinates sites of the well-defined facets. These low coordination sites are likely more abundant on amorphous nanoparticles, which could be one of the factors explaining the higher catalytic activity observed for non-crystalline materials.

Keywords

Water electrolysis
Oxygen Evolution Reaction
Iridium oxide
Nanoparticles
DFT

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