Jibiao Li

Molecular mechanisms of a single H2O diffusion on palladium surfaces

Surface diffusion of a water monomer is not as simple as previously imagined. Using state-of-the-art density functional theory, we have obtained important molecular insights relating to the elementary steps of atop-to-atop diffusion of a water monomer. We provide theoretical evidence for an anisotropic effect of rotation-jump coupling on Pd{100}; the preference of H-down tumbling motion along the nearest-neighbor direction of the square lattice was identified. The tumbling motion is attributed to quantum-tunneling-assisted diffusion, while the next-neighbor motion on the square lattice as well as the nearest-neighbor motion on Pd{111} favors molecular-axis-guided classical hopping motion whenever possible. The physical origin of the classical diffusions is discussed in the framework of the electronic structure. Our study gives useful direction for further studies on molecular couplings in the elementary steps.

Metals Supported Water Monomers: the Bonding Nature Revisited

A single water monomer is known as a hard-to-observe molecule even in the presence of metal surfaces as supporting matrix. This review highlights effort in experimental characterizations and theoretical modeling of transition metals supported water monomers with attention given to its structure and bonding, together with the insights that we have provided into the bonding nature of the water-interactions by the newly employed projected PDOS (partial density of states) difference analysis, which is proved to be an effective tool to be elucidate such bonding nature. The general s-d hybridization and d-shell effect are summarized, and how these effects can be tuned by tailoring local surface configurations is discussed.

Mysterious Waters at Metal Surfaces

Molecular structures of adsorbed waters at metal surfaces are essential to understanding the widespread processes ranging from ice nucleation, to water involved catalytic surface reactions, to many phenomena of biological and astrochemical importance. Instead of providing a comprehensive literature survey, we focus in this review on detailed structural information, such as water orientations and occupation sites, of intact waters at low temperatures and ultrahigh vacuum conditions investigated by various surface techniques. Despite progresses made in direct imaging the surface waters at high resolutions, as exemplified in a close-packed (e.g. Pd(111)) and an open metal surfaces (e.g. Cu(110)) supported waters, structural mysteries remain at diverse metal surfaces. We highlight experimental challenges and discuss structural mysteries in elucidating surface water structures at molecular levels.