Insight into oxygen stability and vacancy formation on Co3O4 model slabs

Spin-polarised periodic density functional simulations were used to study the stability of oxygen on Co3O4 slab models with (1 0 0) and (1 1 0) terminations in order to understand better the oxidative properties of Co3O4. We observed that the PBE + U method gives binding energies and geometrical parameters similar to those obtained for atomic oxygen adsorption at low coverage using the revised version of screened hybrid exchange functional HSE06. Atomic oxygen is most stably bound on a Co3O4(1 1 0)-terminated surface where the oxygen adatom binds above the bridge sites of cobalt atoms with a binding energy of 401 kJ mol−1. On-surface O recombination to O2 leaving a bare slab from the Co3O4(1 1 0) terminations is 116–123 kJ mol−1 more activated than recombination of O on (1 0 0) surfaces. Removal of surface lattice oxygen by an on-surface oxygen producing O2 and leaving a slab with an O vacancy site is at least 65 kJ mol−1 more activated in the (1 1 0) surface than in the (1 0 0) surface.