Investigations of activated carbon catalyst supports from different natural sources

Abstract

We have used a multi-technique approach to allow us to build a consistent picture of the carbons used for catalyst supports and suggest reasons for the differences between the supports. From the catalyst tests it is clear that the nature of the support has a major influence on the catalyst performance. In part, this is the result of the activation method, however, the hydrogen content of the support also influences the activity. SEM pictures show that the characteristic structures present in the starting material are preserved after carbonisation. The inelastic neutron scattering spectra show that this is also true at the atomic level, with carbons from different sources having different patterns of edge termination of the graphitic structures. That different patterns of edge termination are reflected in the INS spectrum in the out-of-plane C–H bending region around 880 cm⁻¹ is supported by DFT calculations. XPS and SIMS measurements show that for all the carbons, oxygenated and non-aromatic structures are located at the surface of the materials and both decrease rapidly with depth. Comparison of a wood-derived activated carbon before and after impregnation with platinum showed changes that were consistent with reactions on the support during impregnation and reduction treatment in generating the final supported precious metal/carbon catalyst. In addition to redox activity in oxygenated sites enhanced sp² type disorder contributes to improved catalyst dispersion.