Novel microreactor and generic model catalyst platform for the study of fast temperature pulsed operation - CO oxidation rate enhancement on Pt

A novel setup to study the effect of fast, high temperature pulses on catalytic reactions has been developed. The system is based on a microreactor and a generic catalyst support, with an integrated heater that allows for temperature changes up to 230 degrees C within 20-30 mu s and temperature measurements with mu s time resolution. Standard microfabrication techniques were used to prepare the catalyst support and the heater element, a 100 nm thick Pt film on a SiO2 terminated Si wafer. Atomic layer deposition (ALD) was used to cover the Pt film with a uniform Al2O3 nanolayer, making sure it solely works as a heater. The Al2O3 terminated wafers could thus be used as a generic platform for the study of supported catalysts under conditions where extremely fast temperature changes occur. ALD was then further used to deposit Pt nanoparticles of various sizes on the Al2O3 surface, serving as model catalysts. CO oxidation was chosen as the test reaction to investigate the concept of temperature pulsed operation and the results show that reaction rates can be accurately controlled and increased significantly by the application of fast, well-controlled temperature pulses, while the power input required to drive the reaction is lower than for steady state operation. Simulations of the reaction kinetics show that reactants desorb from the surface during the fast, high temperature pulses and that the reaction rate enhancement takes place mainly during the relatively slow re-population of the catalyst surface after the temperature pulse.