Kbr windows

TEM was performed by using Jeol JEM-2200FS equipped with a Cs corrector. Raman spectroscopy was performed by using a Witec Alpha 300R spectrometer with a laser excitation wavelength of 785 nm. X-ray photoelectron spectroscopy was performed by using an Escalab 250 spectrometer with an Al x-ray source (1486.6 eV). Nuclear magnetic resonance spectra were recorded on a Bruker DRX500 spectrometer (500 MHz). Infrared spectroscopy was performed by using a Nicolet 6700 FT-IR spectrometer equipped with a demountable cell (Part Num. 162-3600) with a pair of KBr windows (Pike Technologies). Kelvin probe force microscopy was performed by using an SKP5050 Scanning Calvin probe (KP Technology). Electron energy loss and ultraviolet photoelectron spectroscopies were carried out in an ultra-high-vacuum chamber equipped with a VUV-5000 generator (40.8 eV He II laser) and a SES-100 detector. Detailed procedures for sample preparation were presented in Supplementary Methods.

X-ray photoelectron spectroscopy was performed by using an Escalab 250 spectrometer with an Al x-ray source (1486.6 eV). Nuclear magnetic resonance spectra were recorded on a Bruker DRX500 spectrometer (500 MHz). Infrared spectroscopy was performed by using a Nicolet 6700 FT-IR spectrometer equipped with a demountable cell (Part Num. 162–3600) with a pair of KBr windows (Pike Technologies). TEM was performed using a Jeol JEM-2200FS equipped with a Cs corrector. Raman spectroscopy was performed by using a Witec Alpha 300 R spectrometer with a laser excitation wavelength of 785 nm.