Surface and Interface Engineering of Tungsten Oxide for Highly-Efficient Catalysis

The catalytic performance strongly relies on the composition, structure, and property of the material used. Earth-abundant tungsten oxides family (WOx≤3) has received considerable attention in photocatalysis, electrochemistry and catalytic hydrogenation due to its highly tunable structure and unique physicochemical properties. Substantial efforts have been made by us to improve the photocatalytic activity of WOx≤3 by enhancing light harvesting, charge transfer and separation, including defect engineering, morphology control, and hetero-junction construction. Additionally, the semiconductor-to-metal transition of WOx≤3 has been found with the increase of defect concentration, suggesting H2 can be activated on them in a similar way of a metal catalyst. As a result, WO2.72 also can function as a versatile and efficient catalyst for the saturation of olefins and selective transform of nitroarenes to anilines.

Engineering Morphology of Surfaces by Oblique Angle Etching

ABSTRACTDuring a typical chemical etching process growth front morphology generally generates an isotropic rough surface. In this work, we show that it is possible to form a rippled surface morphology through a geometrical self-assembly process using a chemical oblique angle etching technique. We observe in our Monte Carlo simulations that obliquely incident reactive species preferentially etch the hills that are exposed to the beam direction due to the shadowing effect. In addition, species with non-unity sticking (etching) coefficients can be re-emitted from the side walls of the hills and etch the valleys, which at the end can lead to the formation of ripples along the direction of the beam. This mechanism is quite different than the previously reported ripple formation during ion-beam bombarded surfaces where the particles have much higher energies, lower incidence angle and ripple formation is mainly due to physical deformation of the surface. We investigate the ripple formation process in our simulated surfaces for a wide range of etching angle and sticking coefficient values.