Electronic Supplementary Information for: A Mechanistic Study of the Electrochemical Oxygen Reduction on the Model Semiconductor n-Ge(100) by ATR-IR and DFT Simantini Nayak, P. Ulrich Biedermann, Martin Stratmann, Andreas Erbe 1 Experimental vibrational frequencies of reference compounds 1.1 Oxygen-containing species 1.1.1 Raman spectra of KO 2 and O 2 Stable superoxides can be used to check the vibrational frequencies obtained from DFT calculations. To that end, the Raman spectrum of KO 2 powder (ABCR, Karlsruhe, Germany) on a Si wafer was recorded using a Horiba Labram 2 confocal Raman microscope with 633 nm excitation. The spectrum is shown in Figure 1a, with peak maximum at 1145 cm -1 . 1400 1300 1200 1100 1000 900 intensity (a.u.) wavenumber / cm -1 (a) 1800 1700 1600 1500 1400 intensity (a.u.) wavenumber / cm -1 (b) Figure 1: (a) Raman spectrum of solid KO 2 . (b) Raman spectrum of air. A Raman spectrum of air was recorded using the Horiba Labram 2 confocal Raman microscope, but this time with 514 nm excitation at full power of the Ar + laser. The spectrum is shown in Figure 1b, with a peak maximum at (1558±1) cm -1 . 1 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2013