Heating up the OER: Investigation of IrO2 OER Catalysts as Function of Potential and Temperature

Despite intensive investigations for unravelling the water splitting reaction, the catalyst behavior during the oxygen evolution reaction (OER) is still not fully understood. This is especially true under more demanding conditions like high potentials and high temperatures. Rotating disk electrode measurements show a gradual increase of OER current when increasing the temperature up to 80 degrees C. However, strong bubble formation at elevated temperatures makes in-situ characterization of the catalyst challenging. Here we utilize an in-situ electrochemical and heated flow cell, which aims at an efficient removal of bubbles from the catalyst surface and enables structural studies by X-ray absorption spectroscopy (XAS) at temperatures up to 80 degrees C. Changes in the Ir L-3-edge X-ray absorption near edge spectra (XANES) were observed with respect to the white line position and principal components related to structural changes were extracted. At temperatures of 60 degrees C and above, the white line position of XANES spectra reaches a steady state, which is possibly caused by an equilibrium of different Ir oxidation states. These findings provide first spectroscopic insights in the behavior of OER catalysts at elevated temperatures which are typical for industrial applications and rarely addressed until now.

Automated summary

Despite intensive investigations, the behavior of catalysts during the oxygen evolution reaction (OER) at high temperatures is still not fully understood. This study presents spectroscopic insights into OER catalysts at elevated temperatures using in-situ electrochemical techniques and heated flow cell. The findings reveal the steady state of OER catalysts at temperatures above 60 degrees C, suggesting an equilibrium of different oxidation states. This research provides important information for industrial applications and fills a gap in existing studies.