We report an in situ time-resolved high-energy resolution off-resonant spectroscopy (HEROS) study with unprecedented 100 ms time resolution revealing the unoccupied electronic states of platinum during regenerative oxidation and reduction cycles. The study depicted a slowed oxidation step in comparison with reduction. The oxidation cycle is composed of two characteristic stages, namely adsorption of dissociated oxygen followed by partial oxidation of Pt subsurface. Besides improved temporal resolution of the experiment, the detected reduction process of platinum showed no intermediate features and was completed in a single step within a few seconds.
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