Water Dissociative Adsorption on α-Al2O3(112̅0) Is Controlled by Surface Site Undercoordination, Density, and Topology

α-Al2O3 surfaces are common in a wide variety of applications and useful models of more complicated, environmentally abundant, alumino-silicate surfaces. While decades of work have clarified that all properties of these surfaces depend sensitively on crystal face and the presence of even small amounts of water, quantitative insight into this dependence has proven challenging. Overcoming this challenge requires systematic study of the mechanism by which water interacts with various α-Al2O3 surfaces. Such insight is most easily gained for the interaction of small amounts of water with surfaces in ultra high vacuum. In this study we continue our combined theoretical and experimental approach to this problem, previously applied to water interaction with the α-Al2O3(0001) and (1-102) surfaces, to water interaction with the third most stable surface, i.e. the (11-20). Because we characterize all three surfaces using similar tools, it is straightforward to conclude that the (11-20) is most reactive with water. T...