Probing Facet Specific Interaction of 2-Propanol and CoFe2O4 at Near-Ambient Conditions.

The interaction between 2-propanol and low-index facets of cobalt ferrite thin films under near-ambient conditions has been studied using surface-sensitive vibrational sum frequency spectroscopy (vSFS) and ab initio molecular dynamics (AIMD) simulations. The experimental and theoretical findings suggest that 2-propanol undergoes molecular and dissociative adsorption on different facets of CoFe2O4. Dissociation was found to be more prevalent on the (111) surface than on the (001) surface. Under dry conditions, the active regions on the (111) surface consist of Co2+-O2-propoxide-Fe3+ bridges. In contrast, the Co2+ surface atoms are inactive on the (001) surface under dry conditions. The Fe3+ surface atoms are the preferred adsorption sites. Molecular water plays a detrimental role because it competitively adsorbs onto the active sites with 2-propanol, inhibiting its decomposition. Moreover, OH groups with a lower concentration promote the formation of 2-propoxide. These results contrast with our recent study in which 2-propanol remained molecularly adsorbed on the Co3O4 (001) surface. These findings underscore the ambivalent role of hydroxyl groups on surfaces and also highlight the importance of dissociation state and water concentration as critical parameters for 2-propanol activation.