Modern studies of catalytic reaction mechanisms are typically performed in the operando mode, i.e. performing spectroscopy, microscopy and/or diffraction on the functioning (working) catalysts while catalytic activity/selectivity are simultaneosly recorded. Only the operando approach guarantees meaningful structure-activity/selectivity correlations because the active catalyst maybe different from that after synthesis or during ex situ analysis. For long, our group has used synchrotron-based operando methods to evaluate catalytic processes: atmospheric pressure X-ray photoelectron spectroscopy (AP-XPS), X-ray absorption spectroscopy (XAS, NEXAFS, EXAFS) and X-ray diffraction (BESSY (DE), MaxLab (SE), SLS (CH)). This is complemented by lab-based methods such as infrared (FTIR, PM-IRAS) and vibrational sum frequency generation (VSFG) spectroscopy that are also performed at pressures up to 1 bar. Very recent examples include: i) methane reforming on Ni-ZrO2, CuNi-ZrO2 and Ni-ZrO2/CeO2, ii) CO oxidation and H2/CO/O2 reaction (PROX) on Co3O4, Co3O4/CeO2 and CoO, iii) electrochemical water splitting on perovskite-type (LSF) thin film electrodes under potential control. The operando studies provide direct access to reaction-driven surface structure/composition changes as well as to adsorbed reactants, intermediates and spectators. Another asset of the group is to compare the operando results to those obtained for surface science based planar model catalysts under mbar pressures.

Operando studies of working catalysts by synchrotron-based XPS and XAS at atmospheric pressure

253rd National Meeting (2017)

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