The role of CO2 in dehydrogenation of ethylbenzene over pure α-Fe2O3 catalysts with different facets

•α-Fe2O3 nanocrystals with clean (113), (104), and (102) facets exposure.•(113) facets show higher reactivities to EB dehydrogenation in the presence of CO2.•The adsorption behavior of CO2 on different facets results in different activities.•O (III) on α-Fe2O3 is favorable for the adsorption and activation of CO2.

The replacement of superheated steam with CO2 for ethylbenzene (EB) dehydrogenation to produce styrene (ST) is of great importance from both scientific and practical perspectives, while it is still a big challenge to design and synthesize catalysts for dehydrogenation in the presence of CO2. Research into shape-controlled nanocrystals has proved that well-defined facets are of great importance for understanding the catalytic phenomena due to their definite surface structure. In the present work, α-Fe2O3 nanocrystals enclosed by various crystal facets provide us the clue to understand the role of CO2 in dehydrogenation. O(III) (the triply coordinated surface oxygen atom) is found to play an important role in activating CO2 under reaction conditions, which is supported by both experimental and theoretical results. These results have deepened knowledge about the role of CO2 in dehydrogenation over pure α-Fe2O3 catalysts, which is significant in designing relative catalysts rationally.

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