Identification of the active structure under reaction condition is of great importance for rational design of heterogeneous catalysts, but which is often hampered due to their structural complexity. This paper describes the interplay between the surface structure of Co3O4 and the CO2 hydrogenation reaction. Experimental results combined with theoretical calculations show that the Co3O4 with morphology-dependent crystallographic surfaces presents different reducibility and formation energy of oxygen vacancies, thus resulting in distinct product selectivity. In reaction, Co3O4-0h rhombic dodecahedra were completely reduced to metallic Co and CoO, which presents ~ 85% CH4 selectivity. In contrast, Co3O4-2h nanorods were partially reduced to CoO, which exhibits a ~ 95% selectivity to CO. Both the experimental results and theoretical calculation reveal that CoO surface with oxygen vacancies exhibit lower energy barrier for C-O dissociation in CH3O* than Co and perfect CoO surfaces, thereby promoting CH4 formation. Furthermore, we demonstrate the crucial role of the Co3O4 structure in determining the catalytic performance for higher alcohols synthesis over CuCo-based catalysts. As expected, Cu/Co3O4-2h shows nine-fold higher ethanol yield than Cu/Co3O4-0h due to the inhibition for methanation. This work not only provides detailed understanding of structure-performance relationship in CO2 hydrogenation over Co-based catalysts, but also gives guidance for the rational design of catalyst for CO2 hydrogenation. We also expect that the concept of interplay between surface structure and performance can be widely applied in other catalytic systems.

Interplay between structure and product selectivity of CO2 hydrogenation over Co3O4 catalysts

2019 Fall National Meeting

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