The heterogeneous catalysis of oxygen evolution reaction (OER) has received enormous attention as an environmentally benign way of storing the energy from renewable sources in the form of pure hydrogen. While a lot of emphasis has been placed on developing new OER catalysts, our atomistic understanding of activity-stability relationships even for archetypical OER materials such as RuO2 and IrO2 remains incomplete. Herein, we focus on RuO2 and IrO2 as two representative and highly active catalysts to investigate how their activity and corrosion are intertwined mechanistically under the OER conditions. By employing a combination of ab initio molecular dynamics (AIMD) based free-energy simulations to examine the kinetics and mechanism of metal dissolution and the computational hydrogen electrode (CHE) calculations to study the OER thermodynamics, we demonstrate that i) OER and metal dissolution indeed share common reaction intermediates, and ii) the presence of metastable dissolution intermediates at the catalyst surface can significantly reduce the theoretical overpotential of OER. It is still debated for RuO2 and IrO2 whether lattice oxygen is involved in OER. We demonstrate that lattice oxygen participation mechanism (LOM) can be compatible with conventional adsorbate evolving mechanism (AEM) in the presence of both intrinsic and extrinsic defects (metal vacancies, transition metal dopants). The obtained theoretical results are discussed in light of available experimental data.

Computational study of dissolution and oxygen evolution reaction mechanisms in RuO2 and IrO2

ACS Fall 2020 Virtual Meeting

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