Cathodoluminescence of catalyst crystallites

Abstract

Heterogeneous catalysis has played a major role in the development of the chemical industry¹. Metal oxide catalysts, for example, are used in selective oxidation and ammoxidation of hydrocarbons to produce key industrial chemicals. The activity and selectivity of such catalysts are greatly influenced by their microstructural and electronic structure changes under operating conditions. Here we report the first investigation of the electronic properties of small selected areas of catalyst particles, each only a few micrometers in extent, using a scanning electron microscope technique originally developed for characterizing semiconductor materials. The wavelength of the light emitted by selective electron probe stimulation (cathodoluminescence) can be directly related to the local bandgap energy of the material and the intensity of the signal to the point defect level. Some interpretation is required, but there are minimal specimen preparation requirements and the process is essentially non-destructive so that development sequences can be followed. In favourable cases the important aggregations of point defects can be mapped with respect to other microstructural features. An electronic contribution to promoter mechanisms is suggested.