Zhenzhu Cao

Biomass-Swelling Assisted Synthesis of Hierarchical Porous Carbon Fibers for Supercapacitor Electrodes

The preparation of porous materials from renewable energy sources is attracting intensive attention due to in terms of the application/economic advantage, and pore structural design is core in the development of efficient supercapacitors or available porous media. In this work, we focused on the transformation of natural biomass, such as cotton, into more stable porous carbonaceous forms for energy storage in practical applications. Biomorphic cotton fibers are pretreated under the effect of NaOH/urea swelling on cellulose and are subsequently used as a biomass carbon source to mold the porous microtubule structure through a certain degree of calcining. As a merit of its favorable structural features, the hierarchical porous carbon fibers exhibit an enhanced electric double layer capacitance (221.7 F g-1 at 0.3 A g-1) and excellent cycling stability (only 4.6% loss was observed after 6000 cycles at 2 A g-1). A detailed investigation displays that biomass-swelling behavior plays a significant role, not only in improving the surface chemical characteristics of biomorphic cotton fibers but also in facilitating the formation of a hierarchical porous carbon fiber structure. In contrast to traditional methods, nickel foams have been used as the collector for supercapacitor that requiring no additional polymeric binders or carbon black as support or conductive materials. Because of the absence of additive materials, we can further enhance capacitance. This remarkable capacitive performance can be due to sufficient void space within the porous microstructure. By effectively increasing the contact area between the carbon surface and the electrolyte, which can reduce the ion diffusion pathway or buffer the volume change during cycling. This approach opens a novel route to produce the abundantly different morphology of porous biomass-based carbon materials and proposes a green alternative method to meet sustainable development needs.

Electrocatalytic oxidation of formaldehyde on direct electrodeposited graphene–platinum nanoparticles composites electrode

The one-step electrochemical deposition of highly dispersed platinum nanoparticles on graphene to fabricate a new Pt/EG/GC modified electrode for formaldehyde determination in aqueous solution. Catalyst surface morphology was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), the composition analysis was carried out on energy-dispersive X-ray spectroscopy (EDS). The electrochemical performances of the electrode were investigated by cyclic voltammetry, and clear amperometric responses were obtained in the scan process. The correlation coefficient was 0.998 of the linear relation between current values and concentrations, the Pt/EG/GC electrode exhibited a low limit of detection (0.04 mM), high sensitivity (0.0162 mA mM−1) and long working life. These characteristics make the Pt/EG/GC electrode appropriate for the formaldehyde determination based on formaldehyde electric catalytic oxidation.

Enhancing visible light photocatalytic activity of BiOBr/rod-like BiPO4 through a heterojunction by a two-step method

Visible light driven BiOBr/rod-like BiPO4 composites with different BiOBr to BiPO4 molar ratios were fabricated via a facile deposition-precipitation method. X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and Brunauer–Emmett–Teller surface area were used to characterize the as-synthesized samples. Results showed that the BiOBr/rod-like BiPO4 composite with equal mole ratio exhibited the best photocatalytic performance for rhodamine B (RhB) degradation under visible light irradiation. The enhanced photocatalytic performance could be mainly attributed to the effective separation of the photogenerated electrons and holes at the heterojunction interface of p-BiOBr and n-BiPO4.

A novel Ag3PO4/Nb2O5 fiber composite with enhanced photocatalytic performance and stability

A novel Ag3PO4/Nb2O5 fiber composite was fabricated through depositing Ag3PO4 nanoparticles on Nb2O5 fiber surfaces through a facile depositing precipitation approach. The as-prepared Ag3PO4/Nb2O5 photocatalyst was characterized through XRD, SEM, XPS and UV-Vis measurements. SEM results show that biomorphic Nb2O5 fibers have a wrinkled surface and porous walls. The special morphology of the Nb2O5 fibers provided a large amount of voids and interfaces in favor of decorating with Ag3PO4 nanocrystals. The Ag3PO4/Nb2O5 composite photocatalyst exhibits much higher photocatalytic activity for the degradation of rhodamine B than pure Ag3PO4 under simulated sunlight. Such superior photocatalytic activity is mainly attributed to enhanced visible light absorption and effective separation of photogenerated electron–hole pairs derived from the Ag3PO4/Nb2O5 heterojunction. No loss of photocatalytic activity has been observed after four recycles. Moreover, the large size of the Ag3PO4/Nb2O5 composite allows it to be easily separated from the solution.

Microstructure and Ionic Conductivity of Sb-doped Li7La3Zr2O12 Ceramics: Microstructure and Ionic Conductivity of Sb-doped Li7La3Zr2O12 Ceramics

The garnet-related oxides Li7-xLa3Zr2-xSbxO12 (x = 0, 0.075) were prepared by solid-state reaction method. Crystal structure, microstructure, conductivity, and element distribution were characterized for the pure and Sb-doped Li7La3Zr2O12. Ionic conductivity of the Li7La3Zr2O12 is enhanced by Sb doping. An amorphous Li-La-Zr-Al-O thin film which is formed on the grain boundary of Sb-doped samples not only suppresses the abnormal grain growth but also eliminates the pores on the grain boundary. The ionic conductivity of Sb doped Li7-xLa3Zr2-xSbxO12 ceramic with x = 0.075 sintered at 1160°C reaches about 3.40×10 S/cm.采用传统固相反应法制备了锑掺杂的锆镧酸锂固体电解质陶瓷。对陶瓷的晶体结构、显微结构及元素分布、离子电导率进行了研究。结果表明: 少量锑掺杂可明显提高锆镧酸锂固体电解质陶瓷的离子电导率。1160℃烧结的锑掺杂固体电解质中, 晶粒表面形成无定型的薄膜。此薄膜抑制了晶粒生长, 消除了晶界上的气孔, 提高了陶瓷致密度, 提高了陶瓷的离子导电率。1160℃烧结得到的Li 6.925 La 3 Zr 1.925 Sb 0.075 O 12 陶瓷离子电导率高达3.40×10 -4 S/cm。采用传统固相反应法制备了锑掺杂的锆镧酸锂固体电解质陶瓷。对陶瓷的晶体结构、显微结构及元素分布、离子电导率进行了研究。结果表明: 少量锑掺杂可明显提高锆镧酸锂固体电解质陶瓷的离子电导率。1160℃烧结的锑掺杂固体电解质中, 晶粒表面形成无定型的薄膜。此薄膜抑制了晶粒生长, 消除了晶界上的气孔, 提高了陶瓷致密度, 提高了陶瓷的离子导电率。1160℃烧结得到的Li 6.925 La 3 Zr 1.925 Sb 0.075 O 12 陶瓷离子电导率高达3.40×10 -4 S/cm。

Enhancing photocatalytic activity by tuning the ratio of hexagonal and orthorhombic phase Nb2O5 hollow fibers

Cotton was used as template for the fabrication of a biomorphic Nb2O5 photocatalyst with hexagonal and orthorhombic structures. The as-prepared Nb2O5 was characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area and UV-Vis diffused reflectance spectra measurements. The photocatalytic activity of the Nb2O5 fibers was evaluated through degradation of methylene blue (MB) in aqueous solution exposed to UV light. SEM results show that biomorphic Nb2O5 fibers are both hollow and have porous walls. The architectures allow a more accessible surface for the photocatalytic decomposition of dyes molecules. The photocatalytic activity of physically mixed fibers with 75% H-Nb2O5 and 25% O-Nb2O5 phases is superior to those of pure H- and O-Nb2O5 phases, and other samples with different H- and O-Nb2O5 ratios. Such superior photocatalytic activity is mainly due to an optimal balance between the adsorption of MB and the absorption of UV light. Moreover, the large size of the Nb2O5 hollow fibers allows them to be easily separated from the solution.

A NEW HOMOGENEOUS ELECTROCATALYST FOR ELECTROCHEMICAL CARBONYLATION OF METHANOL TO DIMETHYL CARBONATE

Electrosynthesis of dimethyl carbonate (DMC) from methanol and carbon monoxide using an Cu(phen)Cl2 catalyst was achieved at room temperature and atmospheric pressure. The catalytic activity of the ligand 1,10-phenanthroline (phen) and the catalytic system were analyzed. The IR characterization results for the complex catalyst showed that copper ions were coordinated by nitrogen atoms of phen. In addition, the effects of the influencing factors, such as reaction time (t), reaction temperature (T) and the surface area of the working electrode (SWE) were studied.

Effect of temperature on the phase behavior and microstructure of aggregates in SDS/Triton X-100/aH2O systems

ABSTRACT The phase behavior and microstructure of a system containing polyoxyethylene tert-octylphenyl (Triton X-100), sodium dodecyl sulfate (SDS) and water were investigated using polarized optical microscopy (POM), differential scanning calorimetry (DSC) and small-angle X-ray diffraction (XRD). Phase-behavior study revealed that lamellar and hexagonal phases occurred in different compositions, and that lyotropic liquid crystal phases tended to form an H phase with increased Triton X-100 content. The effects of temperature on the phase behavior and microstructure of lyotropic liquid crystals were also studied. Heating induced a change from hexagonal to lamellar phase and from gel to hexagonal phase. POM and small-angle X-ray diffraction (SXRD) revealed that the phase-transition temperature of LLCs increased with increased Triton X-100 content, as further supported by DSC data.

Immortal ring-opening polymerization of lactides with super high monomer to catalyst ratios initiated by zirconium and titanium complexes containing multidentate amino-bis(phenolate) ligands

Zirconium complexes (L2Zr, L = –OC6H2-4-R1-6-R2-2-CH2-N[(CH2)3-N(CH2CH2)2O]-CH2-4-R1-6-R2-C6H2O–, R1 = Me, R2 = tBu, complex 1; R1 = R2 = tBu, complex 2) containing two symmetrical amino-bis(phenolate) ligands were prepared. Moreover, titanium complexes (LTi(OiPr)2, L = –OC6H2-4-R1-6-R2-2-CH2-N[(CH2)3-N(CH2CH2)2O]-CH2-4-R1-6-R2-C6H2O–, R1 = Me, R2 = tBu, complex 3; R1 = R2 = tBu, complex 4) based on symmetrical amino-bis(phenolate) ligands were synthesized. These complexes were characterized by 1H and 13C NMR spectroscopy and elemental analyses. The solid-state structures of complexes 2 and 3 were determined by X-ray diffraction. Complexes 1, 2, 3, and 4 were highly active initiators for the ring-opening polymerization of L-lactide (L-LA) and rac-lactide (rac-LA). The experimental results show that complexes 1 and 2 are highly active and excellent catalysts for the immortal ring-opening polymerization (iROP) of L-lactide and rac-lactide in the melt state. The monomer-to-complex ratio reached 200 000/1, which is the highest feeding molar ratio of lactide so far, to the best of our knowledge. Meanwhile, a narrow polydispersity index (1.11–1.58) of polymers was obtained, and the number-average molecular weight approached 8.64 × 104 g mol−1. The turnover frequency (TOF) reached 6593 h−1, and the polymerization proceeded smoothly even in an air environment.

Dispersion polymerization of acrylamide with living character and controlled morphologies initiated and mediated by cobalt porphyrin

Dispersion polymerization of acrylamide (AM) catalyzed by cobalt porphyrin [cobalt tetramethoxyphenylporphyrin, (TMOP)Co(II)] with the feature of living radical polymerization (LRP) in alcohol/water or dimethylformamide (DMF)/water is described. Well-defined polyacrylamide (PAM) uniform spherical particles with predetermined molecular weight and narrow polydispersity (Mw/Mn = 1.09–1.35) were obtained under mild thermal conditions. Linear first-order kinetics with different feeding ratios of AM and cobalt porphyrin were obtained and the number-average molecular weight (Mn) increased linearly with monomer conversion. However, little research has been reported on (TMOP)Co(II) mediating a living radical dispersion polymerization of acrylamide. The effects of the feeding ratio of monomer and cobalt porphyrin, the solvent, the time of polymerization as well as monomer concentration on the morphology of the spherical particles were investigated. There were increasing trends in the particle size with the increasing concentration of monomer, the time of polymerization and feeding ratio of AM and cobalt porphyrin. The effects of the volume ratio of alcohol or DMF and water were also studied.