Cluster Structure and Dynamics by Scanning Probe Microscopy (VTSPM)


At reaction temperatures (typically a few 100°C), a catalyst surface becomes dynamic and adsorbates, reaction intermediates as well as catalyst particles can move across the support. We use scanning probe microscopy (SPM) to monitor the cluster geometry and stability during a reaction and track mobile species on the surface.

The surface dynamical process that we investigate include

  • cluster-support interplay during reaction, such as reactant spill-over from active sites onto an inert support
  • growth processes on surfaces, including polymerization reactions of small hydrocarbon molecules

Our current focus lies on Pt clusters on oxide surfaces, e.g. Fe3O4(001). Here, we are particularly interested in the role of surface defects on catalyst reactivity and in transport limitations when studying simple test reactions. Using our recently developed FastSTM module, we can measure two to three orders of magnitude faster than with conventional SPM instruments, such that we can measure at video-rate scan frequencies. This allows us to observe surface dynamic processes in situ with atomic resolution, even at elevated temperatures.

The above movie displays the dynamics of an Fe3O4(001) surface at 80°C. Specifically, the elongated bright species which jump between two distinct sites on opposite Fe rows can be identified as H atoms which jump between two O atoms of the substrate.