Multiple Promotional Effects of Vanadium Oxide on Boron Nitride for Oxidative Dehydrogenation of Propane.

Featuring high olefin selectivity, hexagonal boron nitride (h-BN) has emerged recently as an attractive catalyst for oxidative dehydrogenation of propane (ODHP). Herein, we report that dispersion of vanadium oxide onto BN facilitates the oxyfunctionalization of BN to generate more BO x active sites to catalyze ODHP via the Eley-Rideal mechanism and concurrently produce nitric oxide to initiate additional gas-phase radical chemistry and to introduce redox VO x sites to catalyze ODHP via the Mars-van Krevelen mechanism, all of which promote the catalytic performance of BN for ODHP. As a result, loading 0.5 wt % V onto BN has doubled the yield of light alkene (C2-C3) at 540-580 °C, and adding an appropriate concentration of NO in the reactants further enhances the catalytic performance. These results provide a potential strategy for developing efficient h-BN-based catalysts through coupling gas-phase and surface reactions for the ODHP process.

Quantification of critical particle distance for mitigating catalyst sintering.

Supported metal nanoparticles are of universal importance in many industrial catalytic processes. Unfortunately, deactivation of supported metal catalysts via thermally induced sintering is a major concern especially for high-temperature reactions. Here, we demonstrate that the particle distance as an inherent parameter plays a pivotal role in catalyst sintering. We employ carbon black supported platinum for the model study, in which the particle distance is well controlled by changing platinum loading and carbon black supports with varied surface areas. Accordingly, we quantify a critical particle distance of platinum nanoparticles on carbon supports, over which the sintering can be mitigated greatly up to 900 °C. Based on in-situ aberration-corrected high-angle annular dark-field scanning transmission electron and theoretical studies, we find that enlarging particle distance to over the critical distance suppress the particle coalescence, and the critical particle distance itself depends sensitively on the strength of metal-support interactions.

Radical Chemistry and Reaction Mechanisms of Propane Oxidative Dehydrogenation over Hexagonal Boron Nitride Catalysts.

Although hexagonal boron nitride (h-BN) has recently been identified as a highly efficient catalyst for the oxidative dehydrogenation of propane (ODHP) reaction, the reaction mechanisms, especially regarding radical chemistry of this system, remain elusive. Now, the first direct experimental evidence of gas-phase methyl radicals (CH3 . ) in the ODHP reaction over boron-based catalysts is achieved by using online synchrotron vacuum ultraviolet photoionization mass spectroscopy (SVUV-PIMS), which uncovers the existence of gas-phase radical pathways. Combined with density functional theory (DFT) calculations, the results demonstrate that propene is mainly generated on the catalyst surface from the C-H activation of propane, while C2 and C1 products can be formed via both surface-mediated and gas-phase pathways. These observations provide new insights towards understanding the ODHP reaction mechanisms over boron-based catalysts.

Tuning the size of photo-deposited metal nanoparticles via manipulating surface defect structures of TiO2 nanocrystals.

Here we report a new method for controlling photo-deposited metal nanoparticle size by manipulating surface defect structures of TiO2 nanocrystals. Our results demonstrate that the isolated oxygen vacancy could serve as an electron trapper while the oxygen vacancy cluster could act as an electron-hole recombination site in the photo-deposition process.

Exploration research on synthesis and application of a new dye containing di-2-picolyamine.

A newly designed fluorescence dye L based on di-2-picolyamine (DPA) moiety as a chelator was obtained under the protection of N2 at 120°C, and KI as catalyst with relatively better yield. More interestingly, L not only could selectively and sensitively detect Cu2+ ions in aqueous medium but also examine the Cu2+ ions of the actual water samples. Nevertheless, L could be visual in Hela cells with excellent cell permeability, viz, monitoring exogenous Cu2+ ions as well as realizing an "on-off-on" process.