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The interaction between catalyst surfaces and adsorbed oxygen intermediates is critical to catalytic performance for electrochemical water oxidation to oxygen. However, the relationship between adsorption energetics and electrocatalytic activity is primarily assessed for pristine catalyst materials, which leaves much unknown about the dynamics of these properties in relationship to catalyst performance during long-term operation. In this work, we experimentally assess OH and O adsorption on Ca2IrO4 nanoparticles and monitor their evolution during extensive chronoamperometry tests at highly oxidizing potentials in a range of low pH electrolytes. In situ x-ray absorption spectroscopy reveals changes for surface adsorbate energetics and local iridium structures with applied potentials. Increasingly unfavorable adsorption of OH and formation of O intermediates after long-term operation is correlated with severe metal dissolution, distorted [IrO6] octahedral linkages, and a decreased average Ir valence. This work establishes connections between surface adsorption energetics, Ir structure, OER kinetics, and material stability outcomes.
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Cations Affect Water Activation on Pt(111) in Alkaline Media
Water activation, oxidatively to produce surface-bound hydroxide (OH*) or reductively to form surface-bound hydrogen (H*) atoms, is ubiquitous in electrocatalysis. We report the impact of cations on the kinetics of the OH* and H* formation from water on single-crystal Pt(111) in alkaline using fast-scan-rate cyclic voltammetry. Isolating the dependence of the electro-adsorption kinetics on pH and ionic strength led to the observation that ion concentrations affected the OH* formation kinetics more strongly than pH. The H* formation exhibited similar behavior, even though the OH* formation rate was observed to be faster by >10x. We attributed the observed ion concentration effect to cations, given that switching cations (from Na+to Li+) had a bigger impact on the H* and OH* formation rates than switching pH (effectively changing OH–to F–). We hypothesize the cations softened and allowed the interfacial water layer to more easily reorganize. This result suggests that interfacial water disruption should benefit both H* and OH* electro-adsorption kinetics in alkaline electrolytes.
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- Award ID(s):
- 2155157
- PAR ID:
- 10567046
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 172
- Issue:
- 1
- ISSN:
- 0013-4651
- Format(s):
- Medium: X Size: Article No. 016503
- Size(s):
- Article No. 016503
- Sponsoring Org:
- National Science Foundation
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