Water on Atomically-Defined Cobalt Oxide Surfaces Studied by Temperature-Programmed IR Reflection Absorption Spectroscopy and Steady State Isotopic Exchange

Abstract

In this work, we investigate the interaction of water with three different atomically defined cobalt oxide surfaces under ultrahigh vacuum (UHV) conditions using time-resolved and temperature-programmed infrared reflection–absorption spectroscopy (TR-IRAS, TP-IRAS) in combination with isotopic exchange experiments. The three surfaces, CoO(100), CoO(111), and Co3O4(111), are prepared in form of well-ordered films on Ir(100). Very different behavior is observed on the three surfaces, both with respect to D2O adsorption and desorption. On CoO(100), water adsorbs molecularly. It forms extended ice clusters even at low adsorption temperature (200 K) and which desorb molecularly at 200 K (Ea,des ∼ 60 kJ·mol–1). A very small amount of defect sites is observed at which D2O dissociates and forms strongly bound OD groups. On CoO(111), the interaction with ordered facets is very weak and no adsorption occurs at these sites at 200 K. The CoO(111) films expose, however, a higher density of defects as compared to the C...