Influence of heteroatom-doped Fe-carbon sphere catalysts on CO2- mediated oxidative dehydrogenation of ethylbenzene

Distinctly shaping carbon materials together with doping is an excellent approach for tailoring advanced materials. In this study, a series of heteroatom (N, S, P)-doped Fe-carbon sphere catalysts were prepared by a hydrothermal process to explore the effect of unary and binary dopants on the CO2-mediated ethyl benzene oxidative dehydrogenation. Upon doing so, a transformation from quasi to hollow to perfect spheres was observed that takes place due to the increasing hydrolysis rate and attainment of supersaturation. It was shown that each type of heteroatom has a beneficial role in creating specific chemical entities as well as in defining the iron amount of the catalyst. Catalytic activity correlated with XPS and Raman analysis reveal that the direct dehydrogenation of ethylbenzene is controlled by the iron content at low temperatures, while defect sites are the controlling parameter at high temperatures. Under oxidative conditions, the N-doped hierarchical Fe-hollow sphere carbon (Fe-N-C) catalyst shows the highest catalytic performance among all synthesized catalysts due to the cooperative action of pyridinic N species and the Fe3C phase for CO2 activation as well as RWGS reaction promotion.