Stability of hydroxylated (111) and (101) surfaces of monoclinic zirconia: A combined study by DFT and infrared spectroscopy

We report the structure and stability of hydroxylated ((1) over bar 11) and ((1) over tilde 01) surfaces for a water coverage ranging from 0.25 to 1. For the ((1) over bar 11) surface water dissociated at low coverage (theta = 0.25), whereas both dissociated and molecular species coexisted at higher coverage. For the ((1) over tilde 01) surface molecular adsorption was only observed at the highest coverages (theta = 0.75 and theta = 1). The calculated adsorption energy for ((1) over bar 11) ranged from - 1.20 to -0.83 eV for 0 = 0.25 and 0 = 1, respectively. For the ((1) over bar 01) surface the adsorption energies ranged from - 1.50 to - 1.21 eV for 0 = 0.25 and 0 = 1, respectively. The 1-, 2-, and 3-fold coordinated hydroxyl groups were present in our models. Their structure, energetics, and vibrational frequencies were calculated by ab initio techniques and agreed with in situ infrared spectroscopic measurements. The simultaneous presence of hydroxyl groups of different coordination was concluded from both theoretical and experimental results.