Platinum single atoms are grafted by SOMC on morphology-controlled TiO2. Their structure is characterized by EXAFS and other techniques, and their activity and stability in HER and backwards reaction are studied and compared to Pt nanoparticles.

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TiO 2 is considered as one of the most common photocatalysts for UV light-driven photocatalysis. We present here the effect of exposed facets on the photocatalytic features of anatase and rutile TiO 2 crystals using first-principle computations based on the density functional theory (DFT). The four possible low-Miller-index ( 110), ( 101), (100), and (001) surfaces of each crystalline phase are investigated. The most suitable facets for hydrogen and oxygen evolution reactions (HER and OER, respectively) are identified on anatase and rutile TiO 2 from the combination of the anisotropic redox and charge carrier transport properties. Our study demonstrates the (110) anatase surface as the most suitable candidate for OER, followed by the (101) surface, whereas the (001) anatase surface is predicted as the most suitable candidate for HER. For rutile, the two ( 110) and ( 101) surfaces are predicted as the most suitable candidates for OER, while no suitable surface candidate is found for HER in line with the experimental observations showing better activity for HER using anatase than rutile. These findings will guide experimentalists to carefully design (110)-and (001)-oriented anatase TiO 2 material samples for improved photocatalytic water oxidation and proton reduction.

A specific allotrope of titanium dioxide (anatase) was synthesized both with a standard thermodynamic morphology ({101}-anatase) and with a highly anisotropic morphology ({001}-anatase) dominated by the {001} facet (81%). The surface chemistry of both samples after dehydroxylation was studied by 1H NMR and FT-IR. The influence of surface fluorides on the surface chemistry was also studied by 1H NMR, FT-IR and DFT. Full attribution of the IR spectra of anatase with dominant {001} facets could be provided based on experimental data and further confirmed by DFT. Our results showed that chemisorbed H2O molecules are still present on anatase after dehydroxylation at 350 °C, and that the type of surface hydroxyls present on the {001} facet is dependent on the presence of fluorides. They also provided general insight into the nature of the surface species on both fluorinated and fluorine-free anatase. The use of vanadium oxychloride (VOCl3) allowed the determination of the accessibility of the various OH groups spectroscopically observed.

The dominating catalytic approach to aromatic hydrocarbons from renewables, deoxygenation of phenol-rich depolymerized lignin bio-oils, is hard to achieve: hydrodeoxygenation (HDO) of phenols typically leads to the loss of aromaticity and to non-negligible fractions of cyclohexanones and cyclohexanols. Here, we report a catalyst, niobia-supported iridium nanoparticles (Ir@Nb 2 O 5 ), which combines full conversion in the HDO of lignin-derived phenols with appreciable and tunable selectivity for aromatics (25–95%) under mild conditions (200–300 °C, 2.5–10 bar of H 2 ). A simple approach to the removal of Brønsted-acidic sites via Hünig’s base prevents coking and allows reaction conditions ( T > 225 °C, 2.5 bar of H 2 ), promoting high yields of aromatic hydrocarbons.