posted on 2023-10-30, 14:33authored byYingzhen Chen, Christian Rodenbücher, Klaus Wippermann, Carsten Korte
In situ monitoring
of the electrolyte/electrode interfacial processes,
such as the oxygen reduction reaction (ORR), is crucial for the design
of electrolytes for fuel cells. In this study, we investigate the
electrochemical behavior of platinum electrodes in protic ionic liquids
(PILs) by means of in situ Fourier-transform infrared spectroscopy
coupled with cyclic voltammetry. The result provides direct evidence
of the change of water at the Pt electrode surface due to Pt oxide
formation and reduction. A decrease in the interfacial water was observed
in the spectra upon the formation of the Pt oxide. Conversely, the
local water concentration at the electrode surface increases if the
Pt oxide is reduced and the ORR takes place. At the same time, more
cations replace anions on the electrode. The ORR kinetics in the [TFSI]-based
PILs is slower than in the [TfO]-based ones, which could result from
a blockage of catalytic sites by the adsorbed [TFSI] anions. It suggests
that reducing the anion adsorption on the platinum surface could provide
an opportunity to enhance the ORR activity.