In situ ETEM and holography

Measurement of the potenial distribution of Helmholtz layers across interfaces

Our goal is the understanding of the helmholz layer forming on the catalyst - electrolyte interface region. In the presence of water-vapor we observe, that pure platinum reversible forms a disordered surface layer, which modifies the potential gradient across the interface. Such a gradient is assumed to play a central role for electrocatalysis. To measure the potential gradients across the helmholtz layer, one needs a phase retrieval transmission electron microscopy technique with excellent spatial resolution.

Due to the development of an advanced drift correction scheme, we were able to improve the phase-shifting off-axis holography method of Ru et al. to achieve an angstom resolution in the wave function reconstruction. A series of holograms is acquired and a beam tilt is used to induce a phase-shift between the holograms of the series.
In the resulting hologram series the phase of each pixel is fitted to the cosine modulation of the intensity.

Electron beam induced plasma state characterization by Langmuir-Probing
To characterize the electrochemical conditions in enviromental transmission electron microscopy, we analyze the electron beam beam-gas interaction by plasma-diagnostics. For this purpose a specimen holder was transformed into a Langmuir-probe. From current-voltage measurements of noble gases we calculate the relevant plasma-parameters and the energy distribution function of the plasma electrons.