An integrated coordination structure composed of atomic Ni trapped in graphene defects is directly identified by probe-corrected TEM. The tuned electronic structure is considered to be the origin of enhanced oxygen evolution reaction and hydrogen evolution reaction. HIGHLIGHTSAtomic Ni trapped in carbon defects serves as an active site for superb OER and HER Direct identification of the atomic Ni in defects is provided by probecorrected TEM DFT simulations suggest that tuning the electronic structure enhances OER and HER Zhang et al., Chem 4,[285][286][287][288][289][290][291][292][293][294][295][296][297] February 8, 2018 ª SUMMARY Downsizing the catalyst to atomic scale provides an effective way to maximize the atom efficiency and enhance activity for electrocatalysis. Here, we report a concept whereby graphene defects trap atomic Ni species (aNi) inside to form an integrity (aNi@defect). X-ray adsorption characterization and density-functional-theory calculation revealed that the diverse defects in graphene can induce different local electronic densities of state (DOSs) of aNi, which suggests that aNi@defect serves as an active site for unique electrocatalytic reactions. As examples, aNi@G585 is responsible for the oxygen evolution reaction (OER), and aNi@G5775 activates the hydrogen evolution reaction (HER). The derived catalyst exhibits exceptionally good activity for both HER and OER, e.g., an overpotential of 70 mV at 10 mA/cm 2 for HER (analogous to the commercial Pt/C) and 270 mV at 10 mA/cm 2 for OER (much superior to that of Ir oxide).

Synthetic corundum (Al2O3), gibbsite (Al(OH)3), bayerite (Al(OH)3), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement with the expected composition. High resolution Al2p scans showed no significant changes in binding energy, with all values between 73.9 and 74.4 eV. Only bayerite showed two transitions, associated with the presence of amorphous material in the sample. More information about the chemical and crystallographic environment was obtained from the O1s high resolution spectra. Here a clear distinction could be made between oxygen in the crystal structure, hydroxyl groups and adsorbed water. Oxygen in the crystal structure was characterised by a binding energy of about 530.6 eV in all minerals. Hydroxyl groups, present either in the crystal structure or on the surface, exhibited binding energies around 531.9 eV, while water on the surface showed binding energies around 533.0 eV. A distinction could be made between boehmite and pseudoboehmite based on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudoboehmite.

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Hydrothermal growth of high crystallinity Nb(3) O(7) (OH) single crystal nanorod film onto FTO substrate is directly used as the photoanode for DSSCs without calcination. The resultant DSSCs possess an impressive overall efficiency of 6.77%, the highest among all reported DSSCs assembled by niobium oxide-based photoanodes.

In this work, vertically aligned nanorod-like rutile TiO 2 single crystal nanowire bundles were directly grown onto FTO conducting substrates via a facile, one-pot hydrothermal method. The fabricated nanorod-like rutile TiO 2 single crystal nanowire bundles display a diameter range of 150-200 nm and a mean length of 0.9 mm. The nanorod-like bundles assemble by individual single crystal nanowires of 5-7 nm in diameter. The photoanode made of vertically aligned nanorod-like rutile TiO 2 single crystal nanowire bundles shows excellent photoelectrocatalytic activity towards water oxidation, which is almost 3 times higher than that of the photoanode made of vertically aligned anatase TiO 2 nanotube film of similar thickness. The high photoelectrocatalytic activity of the photoanode made of the nanorod-like rutile TiO 2 single crystal nanowire bundles is mainly due to the superior photoelectron transfer property, which has been manifested by the inherent resistance (R 0 ) of the rutile TiO 2 film via a simple photoelectrochemical method. Using this approach, the calculated R 0 values are 52.1 U and 71.0 U for the photoanodes made of vertically aligned nanorod-like rutile TiO 2 single crystal nanowire bundles and the vertically aligned anatase TiO 2 nanotubes, respectively. The lower R 0 of the rutile TiO 2 photoanode means a superior photoelectron transfer property. XPS valence-band spectra analysis indicates that the nanorod-like rutile TiO 2 film has almost identical valence band position (1.95 eV) when compared to the anatase TiO 2 nanotube film, meaning a similar oxidation capability, further confirming the superior photoelectron transport property of the nanorod-like rutile TiO 2 single crystal nanowire bundles.

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In this work, hydrogenated TiO2 nanotubes (H-TNTs) electrodes were successfully fabricated via the anodization of a titanium sheet followed by a hydrogenation process. Oxygen vacancies were induced in the crystalline structure of TiO2 nanotubes (TNTs) as shallow donors that enhance the electronic conductivity of the TNTs. This improvement in the electronic conductivity and photoelectrocatalytic (PEC) performance was confirmed and evaluated by a photoelectrochemical characterization. Most importantly, the H-TNTs electrode was able to degrade potassium hydrogen phthalate (strong adsorbent) and glucose (weak adsorbent) indiscriminately. The corresponding photocurrents at the H-TNTs were 2-fold greater than that of the TNTs samples for the same concentrations of the organic compounds. This suggests that the H-TNTs electrode can be a promising sensor for the PEC determination of individual organic compounds or as an aggregative parameter of organic compounds (e.g., chemical oxygen demand).

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