*Correspondence to: edman.tsang@chem.ox.ac.uk.The conversion of oxygen-rich biomass into hydrocarbon fuels requires efficient hydro-deoxygenation catalysts during the upgrading process. However, traditionally prepared Co-MoS 2 catalysts, although efficient for hydro-desulfurisation, are not appropriate due to their poor activity, sulfur loss and rapid deactivation at elevated temperature. Here, we report the synthesis of MoS 2 monolayer sheets decorated with isolated Co atoms through covalent bonding of Co to sulfur vacancies on the basal planes that, when compared to conventionally prepared samples, exhibit superior activity, selectivity and stability for the hydro-deoxygenation of 4-methylphenol to toluene. The higher activity, allows the reaction temperature to be reduced from the typically used 300 o C to 180 o C and thus allows the catalysis to proceed without sulfur loss and deactivation. Experimental analysis and density functional theory calculations reveal a large number of sites at the interface between the Co and Mo atoms on the MoS 2 basal surface and we ascribe the higher activity to the presence of sulfur vacancies that are created local to the observed Co-S-Mo interfacial sites.
Lindlar catalysts comprising of palladium/calcium carbonate modified with lead acetate and quinoline are widely employed industrially for the partial hydrogenation of alkynes. However, their use is restricted, particularly for food, cosmetic and drug manufacture, due to the extremely toxic nature of lead, and the risk of its leaching from catalyst surface. In addition, the catalysts also exhibit poor selectivities in a number of cases. Here we report that a non-surface modification of palladium gives rise to the formation of an ultra-selective nanocatalyst. Boron atoms are found to take residence in palladium interstitial lattice sites with good chemical and thermal stability. This is favoured due to a strong host-guest electronic interaction when supported palladium nanoparticles are treated with a borane tetrahydrofuran solution. The adsorptive properties of palladium are modified by the subsurface boron atoms and display ultra-selectivity in a number of challenging alkyne hydrogenation reactions, which outclass the performance of Lindlar catalysts.
Hydrated niobium oxides are used as strong solid acids with a wide variety of catalytic applications, yet the correlations between structure and acidity remain unclear. New insights into the structural features giving rise to Lewis and Brønsted acid sites are presently achieved. It appears that Lewis acid sites can arise from lower coordinate NbO and in some cases NbO sites, which are due to the formation of oxygen vacancies in thin and flexible NbO systems. Such structural flexibility of Nb-O systems is particularly pronounced in high surface area nanostructured materials, including few-layer to monolayer or mesoporous NbO·nHO synthesized in the presence of stabilizers. Bulk materials on the other hand only possess a few acid sites due to lower surface areas and structural rigidity: small numbers of Brønsted acid sites on HNbO arise from a protonic structure due to the water content, whereas no acid sites are detected for anhydrous crystalline H-NbO.
Gonadotropin-inhibitory hormone (GnIH) was originally identified in quail as a hypothalamic neuropeptide inhibitor of pituitary gonadotropin synthesis and release. However, GnIH neuronal fibers do not only terminate in the median eminence to control anterior pituitary function but also extend widely in the brain, suggesting it has multiple roles in the regulation of behavior. To identify the role of GnIH neurons in the regulation of behavior, we investigated the effect of RNA interference (RNAi) of the GnIH gene on the behavior of white-crowned sparrows, a highly social songbird species. Administration of small interfering RNA against GnIH precursor mRNA into the third ventricle of male and female birds reduced resting time, spontaneous production of complex vocalizations, and stimulated brief agonistic vocalizations. GnIH RNAi further enhanced song production of short duration in male birds when they were challenged by playbacks of novel male songs. These behaviors resembled those of breeding birds during territorial defense. The overall results suggest that GnIH gene silencing induces arousal. In addition, the activities of male and female birds were negatively correlated with GnIH mRNA expression in the paraventricular nucleus. Density of GnIH neuronal fibers in the ventral tegmental area was decreased by GnIH RNAi treatment in female birds, and the number of gonadotropin-releasing hormone neurons that received close appositions of GnIH neuronal fiber terminals was negatively correlated with the activity of male birds. In summary, GnIH may decrease arousal level resulting in the inhibition of specific motivated behavior such as in reproductive contexts.
With the introduction of Ga 3+ into Cu/ZnO catalyst precursors, a series of catalysts have been prepared using a simple co-precipitation method and tested as catalysts for the synthesis of methanol from CO2 hydrogenation. It is found that the presence of a small amount of Ga 3+ can facilitate thermal deep reduction of ZnO support to Zn atoms under hydrogen prior to catalysis hence a highly active CuZn bimetallic nanoparticle offering catalytic sites is generated. The effect of Ga 3+ incorporation is attributed to the formation of Ga-containing spinel, ZnGa2O4 structure, which creates electronic heterojunction with excess ZnO phase to account for the facilitated reduction of Zn 2+ to Zn 0 to form CuZn when in contact with Cu nanoparticle. A correlation between Zn 0 concentration in the CuZn alloy nanoparticle to the catalytic performance can thus be clearly demonstrated, which shows CO2 conversion and methanol selectivity can be significantly improved by increasing the Zn 0 content in these hetero-junctioned catalysts.
We report a new Pd@Zn core–shell catalyst that offers a significantly higher kinetic barrier to CO/H2O formation in CO2 hydrogenation but facilitates CH3OH production at below 2 MPa with CH3OH selectivity at 70% as compared to 10% over Cu catalysts.
Support-induced strain engineering is useful for modulating the properties of two-dimensional materials. However, controlling strain of planar molecules is technically challenging due to their sub-2 nm lateral size. Additionally, the effect of strain on molecular properties remains poorly understood. Here we show that carbon nanotubes (CNTs) are ideal substrates for inducing optimum properties through molecular curvature. In a tandem-flow electrolyser with monodispersed cobalt phthalocyanine (CoPc) on single-walled CNTs (CoPc/SWCNTs) for CO2 reduction, we achieve a methanol partial current density of >90 mA cm−2 with >60% selectivity, surpassing wide multiwalled CNTs at 16.6%. We report vibronic and X-ray spectroscopies to unravel the distinct local geometries and electronic structures induced by the strong molecule–support interactions. Grand canonical density functional theory confirms that curved CoPc/SWCNTs improve *CO binding to enable subsequent reduction, whereas wide multiwalled CNTs favour CO desorption. Our results show the important role of SWCNTs beyond catalyst dispersion and electron conduction.
Transition metal-doped nickel phosphide nanoparticles with metallic properties are prepared by a simple and facile wet-chemical method. It is shown for the first time that these transition metals: iron, cobalt, manganese, and molybdenum, can atomically substitute nickel in the parent hcp phosphide lattice as a single phase without significant change in its metallic structure and morphology. They are employed as electro-and photocatalysts for hydrogen evolution reaction, which show highly tunable activities dependent on electron filling of their metallic bands and H coverage according to our experimental and theoretical rationalizations. Molybdenum-doped nickel phosphide nanoparticle with lower H coverage exhibits the best hydrogen evolution performance in electrocatalytic hydrogen evolution reaction, which also shows excellent photocatalytic hydrogen production with organic photosensitizer. In addition, cobalt-doped nickel phosphide nanoparticle with higher H coverage with aqueous photosensitizer gives more superior hydrogen evolution rate.
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