Hanzhong Ke

Hydrogenation of N-propylcarbazole over supported ruthenium as a new prototype of liquid organic hydrogen carriers (LOHC)

We report full hydrogenation of N-propylcarbazole in molten state over a supported ruthenium catalyst at 120–150 °C. A remarkably fast reaction rate was achieved with the apparent activation energy of 18.4 kJ mol−1. Two stereoisomers of the final product were identified and the less stable one was found to dominate the product distribution at lower temperatures and/or with shorter reaction times, which is highly beneficial for hydrogen release upon dehydrogenation with better purity and for enhancement of catalyst performance. The optimum conditions for catalytic hydrogenation of N-propylcarbazole were found to be at 120 °C for 60 minutes.

Synthesis of fluorinated SnO2 3D hierarchical structures assembled from nanosheets and their enhanced photocatalytic activity

Fluorinated SnO2 3D hierarchical structures assembled from nanosheets were synthesized via hydrothermal treatment of stannous fluoride in the presence of an appropriate amount of adipic acid. The as-prepared products were characterized in detail by FESEM/TEM/XRD/BET/XPS/UV-vis DRS techniques. The SnO2 nanosheets with tetragonal rutile structure were single-crystalline in nature and the exposed planes should be {11} facets. A small amount of fluorine ions was observed to be adsorbed on the surface of SnO2 physically. It was found that both of F− and adipic acid played important roles in the formation of SnO2 nanostructures. The as-prepared product presented excellent photocatalytic degradation of RhB which reached 100% within 20 min under UV light irradiation.

Effects of peripheral substitutions on the singlet oxygen quantum yields of monophthalocyaninato ytterbium(III) complexes

A new monophthalocyaninato ytterbium(III) complex 5 with eight 3,5-di-t-butylphenoxyl substituents at peripheral positions is synthesized. X-ray structural analysis of 5·CHCl3·MeOH reveals that the Yb3+ ion is seven-coordinate, surrounded by four nitrogen atoms from the phthalocyaninate dianion and three oxygen atoms from the anionic tripodal LOMe− ligand {LOMe− = [(cyclopentadienyl)tris(dimethylphosphito) cobaltate(III)]}. The effects of substituents on the relative singlet oxygen (1O2) quantum yields of monophthalocyaninato ytterbium(III) complexes are investigated through comparison. It is found that the monophthalocyaninato ytterbium(III) complex has higher 1O2 quantum yield than its corresponding phthalocyaninate ligand. The introduction of a 3,5-di-t-butylphenoxy substituent on the microcycle can enhance the yield of singlet oxygen. Due to the heavy-atoms of both iodine and lanthanide ions, the ytterbium(III) complex 4 based on tert-butyl and iodine substituted phthalocyanine ligands has the highest 1O2 quantum yield (0.82).

Effects of fluorine ions on the formation and photocatalytic activities of SnO2 nanoparticles with small sizes

SnO2 nanoparticles with small sizes were synthesized by a simple hydrothermal route with different dosages of fluorine ions. These nanoparticles all showed a typical rutile phase and excessive dosage of fluorine ions would result in other crystallographic phases. The average diameters of the as-prepared products were all smaller than 4 nm. The introduction of fluorine ions had little influence on the morphologies and crystallite sizes, but enhanced the crystallization of the rutile phase and promoted the growth of SnO2 crystallites. XPS patterns showed that some introduced fluorine ions were physically adsorbed on the surface of SnO2 crystals, but not doped in the lattice. The photocatalytic activities were tested by photodecomposition of Rhodamine B (RhB) under a 300 W high-pressure mercury lamp. The results indicated that a suitable amount of fluorine ions on the surface of SnO2 nanoparticles caused significant enhancement of their photocatalytic activities.

Phenylene-bridged perylenediimide-porphyrin acceptors for non-fullerene organic solar cells

New perylenediimide-porphyrin acceptors, 4PDI-ZnP and 2PDI-ZnP, have been facilely synthesized by acid-catalyzed condensation of perylenediimide-substituted benzaldehyde with pyrrole and dipyrromethane, respectively, and subsequent Zn(II)-complexation. 4PDI-ZnP with four perylene diimide (PDI) moieties appended onto the zinc(II)-porphyrin core shows higher electron mobility than 2PDI-ZnP with only two PDI units. The π-conjugation between PDI and porphyrin is significantly weakened by the phenylene linkage twisting them due to steric hindrance, which renders the absorption features from porphyrin and PDI undisturbed in the range of 385–600 nm. For spectral absorption properties perfectly complementary to the common polymer donor PTB7-Th, the two acceptors have been evaluated together with PTB7-Th in non-fullerene bulk heterojunction organic solar cells (BHJ OSCs). High power conversion efficiency of 9.64% was achieved using the blend of 4PDI-ZnP:PTB7-Th for optimal visible sunlight harvesting, favorable morphological properties and efficient charge dissociation upon photon absorption. This represents a new benchmark photovoltaic performance for PDI acceptors and PTB7-Th donor systems. It should be noted that the porphyrin core not only acts as a scaffold for PDI moieties, but also contributes the light-harvesting in near-ultraviolet and violet regions, which is unambiguously demonstrated in single-component BHJ OSCs based on the two acceptors.

Single ion conducting lithium sulfur polymer batteries with improved safety and stability

Li–S secondary batteries use lithium metal as the anode. The safety hazard arising from the Li dendrite formation on the metal surface presents a formidable challenge that has hindered the technology from practical applications for many years. It has been confirmed that tiny and random lithium deposition takes place at the ion depletion layer on the surface of lithium metal. The time required to reach the ion depletion layer can be quantified using Sands equation, in which the time is inversely proportional to the transference number of anions (t−). Therefore, restricting the mobility of anions enables avoidance of ion depletion. In this study, lithium 4-aminophenylsulfonyl(trifluoromethylsulfonyl)imide (LiATFSI) is grafted with poly(ethylene-alt-maleic anhydride) (PEMA, Mw = 100 000–500 000) using a cyclic imide to form a single ion conducting polymer electrolyte (PEMA-graft-LiATFSI). The polymer electrolyte membrane made of PEMA-graft-LiATFSI is capable of withstanding a high current density of ±50 mA cm−2 (normalized to the surface area of the lithium disk) in a lithium symmetric cell. More remarkably, the metallic luster of the lithium foil remains essentially intact even after a galvanostatic cycling test with a current density of ±10 mA cm−2 for over 1600 hours, suggesting that the membrane can effectively suppress Li dendrite formation and thus pave a way to use lithium metal directly as the anode material with sufficient energy capacity and good safety. The lithium–sulfur battery assembled with the membrane as the electrolyte as well as the separator delivered a stable capacity of 780.8 mA h g−1 after 1000 cycles at 1C. This work demonstrates the necessity and fundamental importance of single ion conducting electrolyte membranes for achieving safe and stable performance with high energy density lithium metal secondary batteries.