Ambient-pressure photoelectron spectroscopy for heterogeneous catalysis and electrochemistry

We describe the design and capabilities of a new ambient-pressure X-ray photoelectron spectroscopy system at the Stanford Synchrotron Radiation Lightsource. A unique feature of this system is that samples are illuminated at grazing incidence and with a tightly focused beam, which allows a 50 μm aperture to be placed in the first differential pumping stage of the lens system of the electron spectrometer. The low conductance of the aperture enables surface-sensitive electron spectroscopy of solid surfaces, liquids, and solid–liquid interfaces to be performed operando at pressures as high as 100 Torr. The instrument can also be used to obtain polarization-resolved X-ray absorption spectra using Auger-electron-yield detection. Results for Pt surfaces in ambient-pressure gas environments and for liquid water are presented.