Evolution and Reactivity of Active Oxygen Species on sp2@sp3 Core-Shell Carbon for the Oxidative Dehydrogenation Reaction

Different sp(2)@sp(3) core-shell structures are obtained on nano-diamond by using annealing treatment at increasingly higher temperatures. The resulting nanocarbons can serve as model catalysts to investigate the structural effect on the evolution and chemical nature of oxygen functional groups for oxidative dehydrogenation reactions. We studied in situ reactions and characterization data and found that the initial existence of oxygen-containing groups on a catalyst surface had a low contribution to the catalytic performance. The active oxygen species can be generated promptly in situ by the chemisorption of O-2 under the reaction conditions and involved in catalytic dehydrogenation process following a redox mechanism. For different hybridized nanostructures, the same types of generated active oxygen groups show different catalytic capabilities, which can be regulated by the sp(2)-hybridized carbon fraction of nanodiamond. The ketonic carbonyl groups formed on graphitic onion-like carbon surface are more active and can improve the selectivity to alkenes significantly compared with the initial nanodiamond and traditional carbon nanotubes.