This study reports on the impact of identity and compositions of buffer ions on oxygen evolution reaction (OER) performance at a wide range of pH levels using a model IrOx electrocatalyst. Rigorous microkinetic analysis employing kinetic isotope effects, Tafel analysis, and temperature dependence measurement was conducted to establish rate expression isolated from the diffusion contribution of buffer ions and solution resistance. It was found that the OER kinetics was facile with OH− oxidation compared to H2O, the results of which were highlighted by mitigating over 200 mV overpotential in the presence of buffer to reach 10 mA cm−2. This improvement was ascribed to the involvement of the kinetics of the local OH− supply by the buffering action. Further digesting the kinetic data at various buffer pKa and the solution bulk pH disclosed a trade-off between the exchange current density and the Tafel slope, indicating that the optimal electrolyte condition can be chosen at a different range of current density. This study provides a quantitative guideline for electrolyte engineering to maximize the intrinsic OER performance that electrocatalyst possesses especially at near-neutral pH.
Bibliographical noteKAUST Repository Item: Exported on 2022-06-15
Acknowledged KAUST grant number(s): OSR #4191
Acknowledgements: A part of this work was supported by JSPS KAKENHI Grant Number 19 K23569 and UTokyo-KAUST collaborative research OSR #4191 “Towards Sustainable Production of H2”.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
ASJC Scopus subject areas
- Environmental Chemistry
- Materials Science(all)
- Chemical Engineering(all)