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.

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► A new APXPS system is in operation at SSRL.
► XPS measurements can be performed in 100 Torr gas ambient.
► Solid–liquid interfaces and liquid surfaces can be investigated.
► Grazing X-ray incidence can be advantageous; the gas phase signal is less pronounced.
► Hydroxyl species on Pt(1 1 1) can be stabilized in ambient conditions.