Catalytic Reaction Studies with Model Catalysts Made by Colloidal Lithography

2 Catalytic Reaction Studies with Model Catalysts Made by Colloidal Lithography 

All ex situ prepared catalysts must be activated prior to experiments to remove residual contamination from the preparation procedure and hydrocarbons from ambient air exposures. Such activations normally include an oxidation step followed by a reduction step. The pretreatments may be 

CO oxidation in O2 excess on the fresh model catalyst. XPS analysis indicates stabilization of Pt oxide in the case of Pt/ceria [98]. In contrast, similar measurements on Pt/alumina show that these Pt particles are metallic and the chemical state does not change significantly after several CO oxidation cycles in O2 excess [98]. The long-term lean CO oxidation experiments on Pt/ceria indicate that the catalyst activity gradually changes as a function of CO oxidation experiment time. Extensive CO reduction causes an up-shift of both T50 and E a, which is attributed to C deposition on the catalyst [9], probably via CO disproportionation at CO excess. A lower value of T50 and E can, however, be restored by running a H2 oxidation over the catalyst (cycles 5-7) around stoichiometric conditions a = 0.67). The influ- 

By varying the particle size, shapes, separation, and support on planar model electrocatalysts, the influence of these properties on the electrocatal3dic reactions, e.g., on fuel cell electrodes, can be evaluated systematically. Some new challenges arise, such as the adhesion of the catalyst particles on new types of support materials (e.g., glassy carbon). However, most of the procedures and concepts of preparation and characterization are the same as in heterogeneous catalysis and photocatalysis. 

we give an example where the electrochemical and electrocatalytic properties of nanostructured Pt catalysts supported on glassy carbon, prepared with colloidal lithography, were tested with oxidation of preadsorbed CO, so-called CO-stripping, as a test reaction [99]. The Pt nanoparticles were prepared as described in Fig. 4.11, except that the polystyrene particles were removed by UV-ozone treatment. The particles had an average diameter of 122 11 nm and were about 40 nm high. There was no indication (by AFM 

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