Direct In Situ Raman Spectroscopic Evidence of Oxygen Reduction Reaction Intermediates at High-Index Pt(hkl) Surfaces

The study of the oxygen reduction reaction (ORR) at high-index Pt(hkl) single crystal surfaces has received considerable interest due to their well-ordered, typical atomic structures and superior catalytic activities. However, it is difficult to obtain direct spectral evidence of ORR intermediates during reaction processes, especially at high-index Pt(hkl) surfaces. Herein, in situ Raman spectroscopy has been employed to investigate ORR processes at high-index Pt(hkl) surfaces containing the [011 ̅] crystal zone - i.e. Pt(211) and Pt(311). Through control and isotope substitution experiments, we successfully obtained in situ spectral evidences of OH and OOH at Pt(211) and Pt(311) surfaces. After detailed analysis based on the Raman spectra, it was deduced that the difference in adsorption of OOH at high-index surfaces has a significant effect on the ORR activity. This research illuminates and deepens the understanding of the ORR mechanism on high-index Pt(hkl) surfaces and provides theoretical guidance for the rational design of high activity ORR catalysts.