The structure and chemistry of water at surfaces and interfaces is an unresolved and fundamental topic in many areas of science and technology such as catalysis, electrochemistry and environmental sciences. We use low temperature scanning tunneling microscopy in combination with DFT calculations to study the structure and reactions of ultra thin water films on Ru(0001) at the molecular scale.

 

We present new results on the formation of mixed water-hydroxyl structures following partial dissociation, observed above 130K. We found that the hydrogen produced during partial dissociation can be trapped in the interior of the hexagonal unit cell of the water hydroxyl structures and outside of the hexagons which is thermodynamically more stable. In addition, we studied the structure of water beyond the first layer and discovered that the hexagonal network of the second layer is surprisingly rotated 30° with respect to the first on Ru(0001) as well as on Pd(111). This rotation leads to a bonding structure between the water layers that significantly deviates from the conventional ice-like water model on hexagonal metals. We propose models for this novel structure of the first two water layers based on DFT calculations. Beyond the second water layer, a transition to the growth of compact ice clusters was found.