Heterogeneous Oxidation Catalysis in the Liquid Phase

A02: High-Resolution Nanoelectrochemical Microscopy and Single Particle Electrocatalysis for Activity-Structure Correlation

Prof. Dr. Corina Andronescu • Prof. Dr. Wolfgang Schuhmann

Investigation of catalyst particles or catalyst films, which will be cobalt-based spinel and perovskite oxides including Fe, Mn, or V substitution will be performed by scanning electrochemical cell microscopy (SECCM) on thin-film electrocatalyst libraries and laser-treated thin films (C. Andronescu). Sputtered films with libraries of varying elemental composition will be post-annealed to form single crystalline surface areas which will be determined and localized by electron backscatter diffraction (EBSD). SECCM will be performed on these grains to correlate electrochemical activity for the oxygen evolution reaction (OER) as well as ethylene glycol oxidation with the composition and surface structure of the materials. Photoresist-structured catalyst films on TEM grids and SECCM will provide information about the impact of electrocatalysis on the structure and composition of the material. SECCM will be used to study how heteroelements like iron, vanadium or manganese incorporated in thin-film model catalysts (such as Co3O4) after laser treatment.

The particle-on-the-stick approach will be applied to identify the intrinsic activity of defined catalyst particles such as cobalt-based spinel and perovskite oxides with Fe, Mn, or V substitution (W. Schuhmann). Identical location TEM using a specifically designed nanoelectrode-TEM holder provides access to the electrochemically induced structural modifications of the particle during electrocatalysis in accelerated stress tests at extreme current densities. This approach will be further extended to substrate such as cinnamyl alcohol, ethylene glycol, cyclohexene, cyclohexane, and solvent including water, acetonitrile, and dimethylformamide. 

Finally, to address the knowledge gap between heterogeneous catalysis and electrocatalysis a continuously operated electrochemical flow-through reactor with temperature control and operated with organic electrolytes will be developed. The catalyst materials will be immobilized on electrodes and electrocatalysis at changing temperatures will be performed. The final step is the transition to a heated high-pressure batch reactor equipped with suitable electrochemical abilities. The dependence of the overpotential and the product variation from the pressure, temperature will be evaluated to correlate results from heterogeneous catalysis and electrocatalysis.

(Figure: Left: Different particle-modified nanoelectrodes. The color of the frame is demonstrating the corresponding voltammogram at the right. Right: Linear sweep voltammograms demonstrating the extremely high achievable current density using the particle-at-the-nanoelectrode approach).