RESUMEN
The development of highly active, reusable catalysts for aqueous-phase reactions is challenging. Herein, metallic nickel is encapsulated in a nitrogen-doped carbon-silica composite (SiO2@Ni@NC) as a catalyst for the selective hydrogenation of vanillin in aqueous media. The constructed catalyst achieved 99.8% vanillin conversion and 100% 4-hydroxymethyl-2-methoxyphenol selectivity at room temperature. Based on combined scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman analyses, the satisfactory catalytic performance is attributed to the composite structure consisting of an active metal, carbon, and silica. The hydrophilic silica core promoted dispersion of the catalyst in aqueous media. Moreover, the external hydrophobic NC layer has multiple functions, including preventing oxidation or leaching of the internal metal, acting as a reducing agent to reduce the internal metal, regulating the active-site microenvironment by enriching the concentrations of H2 and organic reactants, and modifying the electronic structure of the active metal via metal-support interactions. Density functional theory calculations indicated that NC facilitates vanillin adsorption and hydrogen dissociation to promote aqueous-phase hydrogenation. This study provides an efficient strategy for constructing encapsulated Ni-based amphiphilic catalysts to upgrade biomass-derived compounds.
RESUMEN
The poor conductivity of sulfur, the shuttle effect and sluggish redox reaction kinetics of lithium polysulfides (LiPSs) are considered the main obstacles to the practical application of Lithium-sulfur (Li-S) batteries. Thus, it is urgent to design multifunctional host materials to eliminate these obstacles. Herein, we designed a hollow flower-like CoTiO3 wrapped by reduced graphene oxide (h-CoTiO3@rGO) as sulfur host materials. The hollow structure of h-CoTiO3@rGO not only endows sufficient space for high sulfur loading, but also physically and chemically confines the shuttle effect of LiPSs through the formation of Co-S chemical bonding. The large specific surface area and excellent electrocatalytic ability of h-CoTiO3@rGO provide amounts of active sites to accelerate the redox reaction of LiPSs. Meanwhile, the conductive reduced graphene oxide (rGO) covered on the surface of CoTiO3 microspheres offers an interconnected conductive network to support the fast electron/ion transfer. Profit from these merits, the battery employing the multifunctional h-CoTiO3@rGO as sulfur host exhibited excellent cycling stability with an ultralow capacity fading of 0.0127 % per cycle after 500 cycles at 1C. Even the battery with high sulfur loading of 5.2 mg/cm2 still delivered a high area capacity of 5.02 mAh/cm2, which was competitive with the commercial Li-ion batteries. Therefore, the competitive capacity and superior cycling stability suggest that the h-CoTiO3@rGO/S cathode is a potential candidate for high-performance Li-S batteries.
RESUMEN
The granin family comprises altogether 7 different proteins originating from the diffuse neuroendocrine system and elements of the central and peripheral nervous systems. The family is dominated by three uniquely acidic members, namely chromogranin A (CgA), chromogranin B (CgB) and secretogranin II (SgII). Since the late 1980s it has become evident that these proteins are proteolytically processed, intragranularly and/or extracellularly into a range of biologically active peptides; a number of them with regulatory properties of physiological and/or pathophysiological significance. The aim of this comprehensive overview is to provide an up-to-date insight into the distribution and properties of the well established granin-derived peptides and their putative roles in homeostatic regulations. Hence, focus is directed to peptides derived from the three main granins, e.g. to the chromogranin A derived vasostatins, betagranins, pancreastatin and catestatins, the chromogranin B-derived secretolytin and the secretogranin II-derived secretoneurin (SN). In addition, the distribution and properties of the chromogranin A-derived peptides prochromacin, chromofungin, WE14, parastatin, GE-25 and serpinins, the CgB-peptide PE-11 and the SgII-peptides EM66 and manserin will also be commented on. Finally, the opposing effects of the CgA-derived vasostatin-I and catestatin and the SgII-derived peptide SN on the integrity of the vasculature, myocardial contractility, angiogenesis in wound healing, inflammatory conditions and tumors will be discussed.