We used ab initio molecular dynamics simulations to compare the activation of 2-propanol on the low index Co₃O₄ (111), (110) and (001) surfaces in dry conditions. The thermal and surface assisted decomposition of a film of 2-propanol to 2-propoxide on the B-termination of each surface was monitored and analyzed. The investigations suggest an activity order of Co₃O₄ (111) > (110) > (001). On all surfaces, the Co³⁺ serve as adsorption sites. On the B-terminated (111) surface, full dissociation of all 2-propanol molecules at the interface is observed, accompanied by a Mars-van Krevelen-type mechanism upon pre-hydroxylation of the surface. The active regions show Co³⁺–O_2-propoxide–Co²⁺ bridges where the coordinatively unsaturated Co²⁺ ions also participate in the adsorption and decomposition of 2-propanol. On the (110) surface, 2-propanol dissociation is driven by temperature, which activates the two-fold coordinatively unsaturated surface oxygens. The (001) surface on which almost no dissociation occurs is the least active. No formation of acetone is observed in the simulations conditions on all surfaces.

CoFe${}_2$O${}_4$ is a promising catalytic material for many chemical reactions. We used ab initio molecular dynamic simulations to study the structure and reactivity of the A- and B-terminations of the low-index CoFe${}_2$O${}_4$(001) surfaces to water adsorption at room temperature. Upon adsorption, water partly dissociates on both termination with a higher dissociation degree on the A-termination (30% versus 19%). The 2-fold coordinated Fe³⁺(tet) in the tetrahedral voids and the 5-fold coordinated Fe³⁺(oct) in the octahedral voids are the main active sites for water dissociation on the A- and B-termination, respectively. Molecular water, hydroxydes, and surface OH resulting from proton transfer to surface oxygens are present on the surfaces. Both water-free surface terminations undergo reconstruction. The outermost Fe³⁺(tet) on the A-termination and B-termination move towards the nearby unoccupied octahedral voids. In the presence of a thin film of 32 water molecules, the reconstructions are partially and completely lifted on the A- and B-termination, respectively.

CoFe2O4 is a promissing catalytic material for many chemical reactions. We have used ab initio molecular dynamic simulations to study the structure and reactivity of the A- and B-terminations of the low index CoFe2O4 (001) surfaces to water adsorption at room temperature. Upon adsorption, water partly dissociates on both termination with a higher dissociation degree on the A- termination (30% versus 19%). The 2-fold coordinated Fe3+(tet) in the tetrahedral voids and the 5-fold coordinated Fe3+(oct) in the octahedral voids are the main active sites for water dissociation on the A- and B-termination, respectively. Molecular water, hydroxydes and surface OH resulting from proton transfer to surface oxygens are present on the surfaces. Both water free sur- face terminations undergo reconstruction. The outermost Fe3+(tet) on the A-termination and B-termination move towards the nearby unoccupied octahedral voids. In the presence of a thin film of 32 water molecules, the reconstructions are partially and completely lifted on the A- and B-termination, respectively.

The interaction of 2-propanol with Co3O4(001) was studied by vibrational sum fre-quency spectroscopy (vSFS) and by ab initio molecular dynamics (AIMD) simulations of 2-propanol dissolved in a water film to gain insight at the molecular level into the pathways of catalytic oxidation. The experimental study has been performed under near ambient condition, where the presence of water vapor is unavoidable, resulting in a water film on the sample and thereby allowing us to mimic the solution-water interface. Both experiment and theory conclude that 2-propanol adsorbs molecularly. The lack of dissociation is attributed to the adsorption geometry of 2-propanol in which the O-H bond does not point towards the surface. Furthermore, the copresent water not only competitively adsorbs on the surface but also inhibits 2-propanol deprotonation. The calculations reveal that the presence of water deactivates the lattice oxygen, thereby reducing the surface activity. This finding sheds light on the multifaceted role of water at the interface for the electrochemical oxidation of 2-propanol in aqueous solution as recently reported. At higher temperatures 2-propanol remains molecularly adsorbedon Co3O4(001) until it desorbs with increasing surface temperature.

We used ab initio molecular dynamics simulations to compare the activation of 2-propanol on the low index Co3O4 (111), (110) and (001) surfaces in dry conditions. The thermal and surface assisted decomposition of a film of 2-propanol to 2-propoxide on the B-termination of each surface was monitored and analyzed. The investigations suggest an activity order of Co3O4 (111) > (110) > (001). On the B-terminated (111) surface, full dissociation of all 2-propanol molecules at the interface is observed, accompanied by a Mars-van Krevelen-type mechanism upon hydroxylation of the surface. On the (110) surface, 2-propanol dissociation is driven by temperature, which activates the two-fold coordinatively unsaturated surface oxygens. The (001) surface on which almost no dissociation occurs is the least active. No formation of acetone is observed in the simulations conditions.