Revealing the Surface Reactivity of Zirconia by Periodic DFT Calculations

ZrO2 is known in chemistry to be a stable material. However, some technological applications point to specific redox reactivity related to surface oxygen composition. In this paper, ab initio calculations are used to characterize structure-reactivity relationships on monoclinic zirconia surfaces as regards thermodynamic stability, electronic structure, and chemical reactivity in reducing conditions. It is shown that the formation of different types of oxygen vacancies is possible on the surfaces of monoclinic zirconia. 2-Fold vacancies are found to induce an important structural relaxation. Moreover, the presence of O vacancies affects the surface electronic structure in two ways: either zirconium sites are reduced or F-centers are formed; the final state depends on the local geometry around the vacancy. Finally, some oxygen vacancy sites are found to be highly reactive toward dihydrogen, leading to its spontaneous dissociation and formation of dihydride species. These results reveal a rich and complex surface chemistry of zirconia with potential applications in many scientific fields.