On the role of microkinetic network structure in the interplay between oxygen evolution reaction and catalyst dissolution

Abstract

Understanding the pathways of oxygen evolution reaction (OER) and the mechanisms of catalyst degradation is of essential importance for developing efficient and stable OER catalysts. Experimentally, a close coupling between OER and catalyst dissolution on metal oxides is reported. In this work, it is analysed how the microkinetic network structure of a generic electrocatalytic cycle, in which a common intermediate causes catalyst dissolution, governs the interplay between electrocatalytic activity and stability. Model discrimination is possible based on the analysis of incorporated microkinetic network structures and the comparison to experimental data. The derived concept is used to analyse the coupling of OER and catalyst dissolution on rutile and reactively sputtered Iridium oxides. For rutile Iridium oxide, the characteristic activity and stability behaviour can be well described by a mono-nuclear, adsorbate evolution mechanism and the chemical type of both competing dissolution and rate-determining OER-step. For the reactively sputtered Iridium oxide surface, experimentally observed characteristics can be captured by the assumption of an additional path via a low oxidation state intermediate, which explains the observed characteristic increase in OER over dissolution selectivity with potential by the competition between electrochemical re-oxidation and chemical dissolution.

Phase- and Surface Composition-Dependent Electrochemical Stability of Ir-Ru Nanoparticles during Oxygen Evolution Reaction

“…2.5 nm). 102 The thermodynamically and microkinetically anticipated Ir dissolution under OER potentials 126,127 can take place via the Ir V /Ir III pathway 128,129 but, given the high OER potentials recorded (E > 1.6 V vs RHE), is most likely to proceed via the formation of the volatile IrO 3 intermediate. 113,130 The gradual decrease in Ir and Ru dissolution and time-dependent convergence toward a steady-state profile under OER operation suggests, however, that the Ir-enriched surface in Ir x Ru 1−x O 2 reaches a meta-stable state under which the AEM is favored.…”

Microkinetic Analysis of the Oxygen Evolution Performance at Different Stages of Iridium Oxide Degradation

“…Experimental studies on rutile structured IrO 2 , prepared by exposing it to increasing calcination temperatures, widely conclude on increasing electrocatalytic stability but decreasing activity. , In a recent interesting work, the kinetics of the stability-related dissolution processes was modeled with a network structure approach . So far, there are no reported microkinetic studies on the effect of degradation on the OER kinetics on rutile IrO 2 itself.…”

“…9,30 In a recent interesting work, the kinetics of the stability-related dissolution processes was modeled with a network structure approach. 31 So far, there are no reported microkinetic studies on the effect of degradation on the OER kinetics on rutile IrO 2 itself. However, the effect of the material degradation on the OER performance is one of the most relevant issues to address to ensure long-term stability.…”

Electrochemical evaluation of the de-/re-activation of oxygen evolving Ir oxide

“…2(a)), hence representing conditions of appreciable coverage by reaction intermediates. 61,62 Again, the log t dependent OER activity decay is discerned, with a change in the slope at ca. 5–10 min, marked with a vertical dashed line in Fig.…”