Catalyst Characterization and in situ Spectroscopy
The Baiker group has also made important contribution to the development of methods for catalyst characterization. They were the first who developed a quantitative model that describes the interdependence of experimental conditions and peak shift in Temperature programmed reduction (TPR) [5.a]. A criteria has been derived which allows to adjust the experimental parameters to achieve optimum sensitivity. Pulse thermal analysis (PTA) [5.b] has been developed in Baiker’s laboratory and applied for a variety of investigations. More recently the group has greatly contributed to the development of methods for investigating catalytic liquid-solid interfaces. These methods, include in situ ATR-IR spectroscopy [5.c], PM-IRRAS [5.d] enabling simultaneous in situ monitoring of the surface and gas- or liquid phase species, and in situ X-ray absorption spectroscopy [5.e]. A variety of new in situ cells have been developed for the investigation of liquid solid-interfaces under reaction conditions, including high pressure cells for the study of reactions in supercritical media. ATR- modulation excitation spectroscopy with phase sensitive detection has been developed providing the possibility to discriminate static and dynamic surface species. Criteria have been given that are essential for the design of cells for in situ studies where the elucidation of structure-activity relationships is targeted. Some of the research in this field has been summarized in recent reviews. The in situ studies, which have often been combined with video-monitoring of the phase behaviour have brought interesting new molecular insight into a variety of liquid-solid interfaces, including chirally modified metals, mixed oxides and organometallic complexes immobilized on functionalized silica.
[5.a] Temperature Programmed Reduction: Parametric Sensitivity and Estimation of Kinetic Parameters, D. Monti and A. Baiker, J. Catal., 83, 323 (1983). Characterization of V2O /TiO5 Eurocat Samples by Temperature Programmed Reduction, R. Köppel, J. Nickl and A. Baiker, Catal. Today, 20, 45 (1994).
[5.b] Influence of Experimental Conditions on Kinetic Parameters of Gas-Solid Reactions - Parametric Sensitivity of Thermal Analysis, B. Roduit, M. Maciejewski and A. Baiker, Thermochimica Acta, 282/283, 101 (1996).
349 Novel Pulse Thermal Analysis and its Potential for Investigating Gas-Solid Reactions, M. Maciejewski, C.A. Müller, R. Tschan, W.D. Emmerich and A. Baiker, Thermochim. Acta, 295, 167 (1997).
[5.c] Pt and Pt/Al2O3 Thin Films for Investigation of Catalytic Solid-Liquid Interfaces by ATR-IR Spectroscopy: CO Adsorption, H2-Induced Recon-struction and Surface Enhanced Absorption, D. Ferri, T. Bürgi and A. Baiker, J. Phys. Chem. B., 105, 3187 (2001).
An ATR-IR Flow-Through Cell for Concentration Modulation Excitation Spectroscopy: Diffusion Experiments and Simulations, A. Urakawa, R. Wirz, T. Bürgi and A. Baiker, J. Phys. Chem. B, 107, 13061 (2003).
[5.d] Simultaneous In Situ Monitoring of Surface/Gas Species and Surface Properties by Modulation Excitation PM-IRRAS: CO Oxidation over Pt Film, A. Urakawa, T. Bürgi, H. P. Schläpfer and A. Baiker, J. Chem. Phys., 124 (5), Art. No. 054717 (2006).
Design and Performance of a Flow-through PM-IRRAS Cell for Time-resolved Simultaneous Surface and Liquid Phase Detection under Concentration and Temperature Perturbations, D.M. Meier, A. Urakawa, R. Mäder and A. Baiker, Rev. Sci. Instrum., 80 (9), Art. No 094101(2009).
[5.e] X-Ray Absorption Studies under Reaction Conditions – Opportunities and Limitations of In Situ Monitoring and Time Resolved Studies of Heterogeneous Catalysts, J.D. Grunwaldt, M. Caravati, S. Hannemann and A. Baiker, Phys. Chem. Chem. Phys., 6, 3037 (2004)
High-Pressure In situ X-Ray Absorption Spectroscopy Cell for Studying Simultaneously the Liquid Phase and the Solid-Liquid Interphase, J.D. Grunwaldt, M. Ramin, M. Rohr and A. Baiker, Rev. Sci. Instrum, 76, 4104 (2005).