Latest ArticlesMesoporous carbon supported with transition metals nanoparticles performs desired activities for oxygen reduction reaction (ORR) and clean energy conversion devices such as Zn–air batteries. In this work, we synthesized N-doped mesoporous carbon loaded with cobalt nanoparticles (CoMCN) through self-assembly method. There are sufficient mesopores on the carbon substrate which stem from the pore-forming agent. These mesopores can provide enough accessible active sites and profitable charge/mass transport for ORR. The high content of pyridinic and graphitic N is beneficial for promoting O2 adsorption and reduction. The smaller value of ID/IG indicates the higher degree of graphitization of CoMCN, providing better electronic conductivity. The half-wave potential of CoMCN is 0.865 V in basic solution, which is 24 mV more positive than that of the commercial Pt/C (0.841 V). In addition, CoMCN performs excellent methanol tolerance and stability under both basic and acidic conditions. The Zn–air battery assembled with CoMCN performs the larger power density and open-circuit voltage than the commercial Pt/C-based battery, indicating the potential application in energy conversion systems. This work provides thoughtful ideas for fabricating transition metal nanoparticles based porous carbon for electrocatalysis and metal–air batteries.
Superior bifunctional electrocatalysts with ultra-high stability and excellent efficiency are crucial to boost the oxygen evolution reaction (OER) and the hydrogen evolution reduction (HER) in the overall water splitting (OWS) for the sustainable production of clean fuels. Herein, comprehensive density functional theory (DFT) computations were performed to explore the potential of several single transition metal (TM) atoms anchored on various S-doped black phosphorenes (TM/Snx-BP) for bifunctional OWS electrocatalysis. The results revealed that these candidates display good stability, excellent electrical conductivity, and diverse spin moments. Furthermore, the Rh/S12-BP catalyst was identified as an eligible bifunctional catalyst for OWS process due to the low overpotentials for OER (0.43 V) and HER (0.02 V), in which Rh and its adjacent P atoms were identified as the active sites. Based on the computed Gibbs free energies of OH*, O*, OOH* and H*, the corresponding volcano plots for OER and HER were established. Interestingly, the spin moments and the charge distribution of the active sites determine the catalytic trends of OER and HER. Our findings not only propose a promising bifunctional catalyst for OWS, but also widen the potential application of BP in electrocatalysis.
Fe-Nx sites have been identified as core descriptors for Fe-N/C based oxygen reduction reaction catalysts. However, the low density and less utilization of Fe-Nx sites render these catalysts with inefficient catalytic performance. Herein, we develop an organic carboxylate-assisted engineering to construct Fe, N co-doped porous carbon interlinked carbon nanotubes (Fe/N-CCNTs) with high-density and sufficiently exposed Fe-Nx sites based on self-catalyzed effect. The existing forms of Fe include Fe-imidazole configuration and coordination with unsaturated Zn sites via organic carboxylate as linkers, leading to high-density Fe-Nx sites after pyrolysis. Besides, hexatomic carbon rings of organic carboxylate lower cyclization energy barrier for CNT formation, resulting in CNTs interlinked with separated active sites through "active point-conductive line-active point" connections. The optimal sample (Fe-BOAc-PNC) exhibits the onset potential of 0.93 V (vs. RHE) and half-wave potential of 0.84 V in alkaline solution. The liquid-state Zn-air battery (ZAB) employing Fe-BOAc-PNC generates large power density (160 mW/cm2) and stability over 160 h. Moreover, the assembled flexible ZAB displays superb power density of 93 mW/cm2 with robust flexibility. This work provides an insightful perspective for designing Fe-N/C catalysts with high-density and sufficiently exposed active sites for energy storage application.
Co3O4 has been widely explored in electrocatalytic 5-hydroxymethyl-furfural (HMF) oxidation. However, the poor intrinsic ability has seriously limited its electrochemical ability. Heteroatom-doping is an efficient method to enhance the electrocatalytic ability of catalyst by regulating electronic structure. Herein, we have modulated the electronic structure of Co3O4 by high valance Mo6+-doping. With the introduction of Mo6+, the content of Co2+ was increased and metal-oxygen bond was strength. Electrochemical results suggested that the electrocatalytic ability of Co3O4 towards HMF oxidation has been dramatically improved and reaction kinetics has been fasten. Theoretical calculations demonstrated that the surrounding cobalt sites after Mo6+-doping with assembled electron has a strong adsorption ability towards HMF molecule leading to more favourable oxidation of HMF. Post characterizations demonstrated pristine Co3O4 structure was kept after electrolysis cycles and CoOOH active species were formed. This work provides a valuable reference for developing efficient heteroatom-doped electrocatalysts for HMF oxidation.
A highly efficient coupling of glycosyl stannanes and sulfonium salts enabled by synergistic Pd/Cu catalysis is disclosed, facilitating the construction of C-aryl/alkenyl glycals under mild conditions in high yields. The protocol tolerates a wide scope of functional groups including ketone, cyano, ester, amide, nitro, halide. The one-pot formal CH glycosylation starting from arene is demonstrated with a reaction sequence of dibenzothiophenylation/Stille coupling. Besides, a gram-scale reaction is performed successfully, showing the high applicability of this protocol.
[1n]metacyclophanes are a class of important building blocks for supramolecular assembly of artificial capsules. Herein we present the preparation and properties of a novel polyfluorinated macrocycle meta-WreathArene, a C2-symmetrical [14]metacyclophane. Adopting a cone conformation in acetone solution, the macrocycle can form dimer capsules through hydrogen bonds induced by chloride anions. Each dimer capsule consists of two meta-WreathArene and two chloride anions, and has been unambiguously characterized both in solution and in solid state.
Prodrug self-delivery carriers with targeting that specifically responded to tumor microenvironments have good potential to improve the application dilemma of approved clinical therapeutic drugs (systemic distribution and side effects). It's noted the conversion of gemcitabine (GEM) to inactive ingredients under the action of cytidine deaminase (CDA) during metabolism in vivo limits its clinical effect. A high level of reactive oxygen species (ROS) results in a high level of oxidative stress in tumor cells, which changes the expression of CDA and optimizes the metabolism of GEM in vivo and overcome drug resistance. In this study, the ROS responsive and ROS self-supplied prodrug of artemisia (ART)-thioacetal bond (TK)-GEM was synthesized and self-vectors based on ART-TK-GEM (TK@FA NPs) was prepared by using nano precipitation. ROS responsive characteristics ensure specific release of prodrugs in tumor cells with high level of ROS thereby reducing side effects on normal cells and tissues. The endogenous ROS and newly generated ROS by ART can reduce the expression of CDA and optimizes the metabolism of GEM, and the accumulated ROS can also induce apoptosis of tumor cells, realizing synergistic anti-tumor effect of chemical drugs and traditional Chinese medicines. This paper proposes a simple method by using clinically approved drugs to improve the insufficient effect of existing chemotherapy and overcome resistance, which has potential to appropriately shorten the drug development cycle and accelerate the clinical investigation of drugs.
Ultrathin two-dimensional metal-organic framework nanosheets have emerged as a promising kind of heterogeneous catalysts. Herein, we report a new kind of 2D porphyrinic metal-organic framework nanosheets of Rh2-PCN-222, which was prepared from the self-assembly of the metalloporphyrin ligand Rh(TCPP)(DCB) (TCPP = 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin; DCB = 3,4-dichlorobenzene) and ZrCl4 in the presence of two kinds of monocarboxylic acids as the modulating reagent. The thickness of Rh2-PCN-222 nanosheets was characterized by atomic force microscopy (AFM) and determined to be 5.4-9.6 nm. It was found that the axial aryl dichlorophenyl substituent, which controlled the anisotropic growth of MOFs, was essential for the formation of nanosheets. Catalytic results showed that Rh2-PCN-222 nanosheets were efficient for CO2 transformation.
Selenium plays various biological functions in the form of selenoprotein in human body. Brain is one of the most abundant organs of selenoprotein, which plays an important role in maintaining brain redox homeostasis, signal transduction pathway regulation and neuroimmune regulation. Yet, nano-selenium have attracted much attention for their high bioavailability and low toxicity. Nano-selenium are of great application potential in field of biomedical nervous system. Recently, investigation on selenoprotein and nano-selenium has gradually become a new hotspot for the important functions of selenium in human nervous system. In this article, we wish to review recent progresses and give a perspective.
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