Oxidative Dehydrogenation on Nanocarbon: Revealing the Catalytic Mechanism using Model Catalysts

Abstract

Model catalysts offer a direct method to determine the active-site structures and mechanisms on nanocarbon catalysts. In this report, we show that the ketonic carbonyl groups are the catalytic center of the nanocarbon-catalyzed alkane oxidative dehydrogenation (ODH) reaction, and we reveal the catalytic mechanism using conjugated polymeric model catalysts containing only ketonic carbonyl groups. An in situ infrared (IR) analysis provides spectroscopic evidence of the “working” configurations of the active sites in association with the redox cycle of the ketonic carbonyl-hydroxyl pairs. Carbonyl reduction (H abstraction from hydrocarbon) is shown to be a kinetically relevant step. An 18O isotope tracer experiment further shows that the activation and exchange of molecular oxygen at the surface active sites are fast processes under common reaction conditions.