The Interplay between Structure and Product Selectivity of CO₂ Hydrogenation

Identification of the active structure under reaction conditions is of great importance for the rational design of heterogeneous catalysts. However, this is often hampered by their structural complexity. The interplay between the surface structure of Co₃ O₄ and the CO₂ hydrogenation is described. Co₃ O₄ with morphology-dependent crystallographic surfaces presents different reducibility and formation energy of oxygen vacancies, thus resulting in distinct steady-state composition and product selectivity. Co₃ O₄ -0 h rhombic dodecahedra were completely reduced to Co⁰ and CoO, which presents circa 85 % CH₄ selectivity. In contrast, Co₃ O₄ -2 h nanorods were partially reduced to CoO, which exhibits a circa 95 % CO selectivity. The crucial role of the Co₃ O₄ structure in determining the catalytic performance for higher alcohol synthesis over CuCo-based catalysts is demonstrated. As expected, Cu/Co₃ O₄ -2 h shows nine-fold higher ethanol yield than Cu/Co₃ O₄ -0 h owing to the inhibition for methanation.