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Free-standing two-dimensional (FS-2D) materials of covalent or ionic bonds can be prepared through mechanical exfoliation by virtue of their intrinsic layered crystal structures. Here, following this strategy, it was reported the fabrication of large-area FS-2D Au films with controllable lattice orientations via an electrochemical hydrogen-detaching method. It was further characterized the catalytic properties of FS-2D Au. The (111)-oriented FS-2D Au with 20 nm in thickness shows a catalytic conversion up to 43.8% for the oxidation of cyclohexane as a model reaction system, a result of more than double of generally reported values. The exceptionally high catalytic activity could be attributed to the flexible structure of the FS-2D Au catalyst, which differs from the rigid structure of general catalysts. The results give useful implications for large-scale productions of a variety of FS-2D metals with controllable orientations, by which their applications may not be confined to catalysis chemistry. [ABSTRACT FROM AUTHOR]

The environmental-friendly hematite iron oxide (α-FeO) has important application prospects in the photocatalysis field owing to its narrow indirect band gap. Here, we report a band gap engineering of α-FeO by incorporation of electrochemically-generated atomic hydrogen at moderate conditions. The ultraviolet-visible spectra show the reduction of the α-FeO band gap after hydrogenation and the absorption region from 200-800 nm is enhanced, especially in the visible light region. First principles calculation reveals the mixing of the new hybrid energy level with the valence band top resulting in a decrease in the band gap of α-FeO. Further photocatalytic degradation experiments of dyes demonstrate that the photocatalytic efficiency of α-FeO can be greatly enhanced by the atomic hydrogen incorporation. The hydrogenated α-FeO can be easily recycled by magnets and has good photocatalytic stability. These findings offer possibilities for utilizing this inexpensive and earth-abundant oxide materials in the pollution controlling areas. [ABSTRACT FROM AUTHOR]

Hydrogen behavior in oxides has triggered much interest for its scientific and technological importance in a wide range of research fields from novel ion conductors to astrochemistry. Here, we report a giant conductivity enhancement in ZnFe2O4 ferrite insulators to the metallic state by over eleven orders of magnitude induced by electrochemically generated atomic hydrogen at room temperature. The conductivity and the amount of incorporated hydrogen increased in an exponential function with time. An activation energy for the atomic hydrogen chemisorption was measured to be 8.23 kJ mol−1. Quantitative kinetics correlations among the adsorption of atomic hydrogen, hydrogen incorporation and conductivity enhancement are established, based on which hydrogen incorporation process is clarified herein. We demonstrate that the hydrogen incorporation in oxides can be adjusted by manipulating the kinetic factors. These findings have implications for research into hydrogen behavior in oxides in environments containing hydrogen atoms and offer possibilities for utilizing and controlling the modifications of oxide materials induced by atomic hydrogen. [ABSTRACT FROM AUTHOR]