μ-reactor measurements of catalytic activity of mass selected nano-particles

The work of this thesis revolves around catalytic activity measurements of nano-particles tested using a μ-reactor platform, developed and produced at DTU, in a collaboration between CINF and Nanotech.
The thesis contains the results from two separate research projects; both utilising μ-reactors in combination with surface science techniques and computer simulations. The first project described is a study of hydrogen dissociation on mono-disperse platinum clusters. The second project studies methanation from carbon monoxide and hydrogen on nano-particles of nickel-iron alloys. The second study is a work in progress, and the corresponding chapter aims to summarise the results so far. Other projects are not included in the thesis because they are inconclusive or dead ends. Hydrogen dissociation was studied by the H₂/D₂ exchange reaction on SiO₂-supported mono-disperse platinum clusters in a -reactor. The reaction was tested under ambient pressures and temperatures ranging from room temperature to 180 °C. The initial ambition was to study size effects on the chemical activity of clusters, but experimental challenges prevented a final conclusion on cluster size effects. Using Pt₈ cluster  samples it was found that minute amounts of oxygen present in the gas stream would change the clusters ability to dissociate hydrogen. Reaction products were analysed with quadrupole mass spectrometry. The catalyst was characterized before and after chemical testing using XPS and ISS, proving the catalyst to be highly stable. DFT simulations demonstrated that even a single oxygen atom binds strongly to SiO₂-supported Pt8 clusters and changes the morphology and chemical properties of the cluster.
Catalytic methanation reaction from CO and H₂ was studied on Ni₇₅Fe₂₅ nano-particles with sizes 3.5nm, 5nm, 7nm and 9nm. The presented data is a work in progress, but initial results show a tendency of 7nm particles being most active. The catalyst is characterized before and after chemical activity measurements using ISS, XPS, and SEM to ensure a clean surface and consistent deposition. Plans for the immediate future involve reproducing activity measurements on all sample sizes and more consistent characterisation with ISS and XPS. An ambitious plan is to do a similar size study on pure nickel nano-particles, to examine differences and similarities between the catalysts under reaction conditions.