Nitrate (NO3 −) is an ubiquitous groundwater contaminant and is detrimental to human health. Bimetallic palladium-based catalysts have been found to be promising for treating nitrate (and nitrite, NO2 −) contaminated waters. Those containing indium (In) are unusually active, but the mechanistic explanation for catalyst performance remains largely unproven. We report that In deposited on Pd nanoparticles (NPs) (“In-on-Pd NPs”) shows room-temperature nitrate catalytic reduction activity that varies with volcano-shape dependence on In surface coverage. The most active catalyst had an In surface coverage of 40%, with a pseudo-first order normalized rate constant of k cat ∼ 7.6 L gsurface-metal −1 min−1, whereas monometallic Pd NPs and In2O3 have nondetectible activity for nitrate reduction. X-ray absorption spectroscopy (XAS) results indicated that In is in oxidized form in the as-synthesized catalyst; it reduces to zerovalent metal in the presence of H2 and reoxidizes following NO3 − contact. Selectivity in excess of 95% to nontoxic N2 was observed for all the catalysts. Density functional theory (DFT) simulations suggest that submonolayer coverage amounts of metallic In provide strong binding sites for nitrate adsorption and they lower the activation barrier for the nitrate-to-nitrite reduction step. This improved understanding of the In active site expands the prospects of improved denitrification using metal-on-metal catalysts.

ClC-3 is a voltage-gated Cl−channel that is highly conserved and widely expressed, although its function, localization, and properties remain a matter of considerable debate. In this study, we have shown that heterologous expression of ClC-3 in either Chinese hamster ovary (CHO-K1) or human hepatoma (Huh-7) cells results in the formation of large, acidic vesicular structures within cells. Vesicle formation is prevented by bafilomycin, an inhibitor of the vacuolar ATPase, and is not induced by an E224A mutant of ClC-3 with altered channel activity. This demonstrates that vesicle formation requires both proton pumping and Cl−channel activity. Manipulation of the intracellular Cl−concentration demonstrated that the ClC-3-associated vesicles shrink and swell consistent with a highly Cl−-permeable membrane. The ClC-3 vesicles were identified as lysosomes based on their colocalization with the lysosome-associated proteins lamp-1, lamp-2, and cathepsin D and on their failure to colocalize with fluorescently labeled endosomes. We conclude that ClC-3 is an intracellular channel that conducts Cl− when it is present in intracellular vesicles. Its overexpression results in its appearance in enlarged lysosome-like structures where it contributes to acidification by charge neutralization.

Gold has been proposed as an environmentally friendly catalyst for acetylene hydrochlorination for vinyl chloride monomer synthesis by replacing the commercially used mercury catalyst. However, long life with excellent activity of is difficult to achieve since gold is readily reduced to metallic nano-particles. The stability of gold limits its industrial application. In this paper, we promoted gold with bismuth for the hydrochlorination of acetylene. It was found that the Bi promotion leads to partial reduction to AuCl, rather than the complete reduction of Au to metallic nano-particles in the absence of Bi. The optimized catalyst with a molar ratio of Bi:Au=3:1 (0.3 wt% Au) showed comparable reactivity to 1.0 wt% Au catalyst and significantly improved stability. Furthermore, the gold-bismuth catalyst had higher activity and stability than the commercial mercury catalyst, is less toxic and more environmental-friendly, making it a potentially green mercuryfree industrial catalyst for acetylene hydrochlorination.

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Activity and selectivity of glycerol oxidation were highly dependent upon Pd surface coverage of Pd-on-Au bimetallic catalysts.