Yuxian Xu

Preparation and characterization of electrospun La1−xCexCoOδ: Application to catalytic oxidation of benzene

An electrospinning with calcination process was employed for the synthesis of La1-xCexCoOδ (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0) oxides. These catalysts were investigated in terms of total benzene oxidation, and characterized by means of XRD, BET, H2-TPR, SEM, XPS, and TEM techniques. The results show that the amount of Ce doping obviously affects the physicochemical and catalytic properties of La1-xCexCoOδ, and when x=1.0, CeCoOδ exhibits the best activity and highly thermal durability for catalytic oxidation of benzene. Additionally, it is demonstrated that the increased activity over perovskite phase dominated oxides is ascribed to a larger surface area while the activity enhancement over metal oxides mainly results from a higher valance of Co and better redox property.

The role of Cu species in electrospun CuO–CeO2 nanofibers for total benzene oxidation

CuO–CeO2 nanofibers with relatively high surface area (EL-CuCe) have been successfully prepared by the electrospinning method and investigated for total benzene oxidation. The improved low-temperature performance of EL-CuCe compared to ST-CuCe (prepared by the surfactant-templated method) is attributed to the better reducibility of Cu ions that are incorporated into the ceria lattice. Moreover, more oxygen vacancies and weakly bound oxygen species (e.g., O2−, O22− or O−) observed on EL-CuCe keep in step with its higher low-temperature oxidation activity. However, without small amounts of bulk CuO, reduction of some surface ceria occurs at 480 °C for EL-CuCe, which probably accounts for its unsatisfactory high temperature performance.

Design of Cu–Ce co-doped TiO2 for improved photocatalysis

The fast recombination of photo-generated conduction band electrons (ecb−) and valance band holes (hvb+) of TiO2 results in an unsatisfactory photocatalytic performance for organic degradation. To increase the efficiency of charge separation, TiO2 was modified by Cu–Ce co-doping considering the better redox properties of copper–ceria oxide with respect to the single oxide, i.e., an easier electron capturing ability. An optimal Cu–Ce co-doped TiO2 with the initial molar ratio of Cu/Ce at 3:1 was prepared by a hydrothermal method with the aim to greatly promote the charge separation, and characterized by XRD, BET, DRS, PL, HR-TEM, and XPS techniques. Upon ultraviolet light irradiation, it exhibits significantly enhanced photocatalytic activity, about 5.8 times that of Ti–HF. The presence of Cu2+ and Ce3+/Ce4+ benefits electrons captured by molecular oxygen, while an increased hydroxyl groups upon Cu–Ce co-doping consume more holes, resulting in prolonged lifetime of photo-generated carriers. Moreover, it is proved that electron transfers preferably from conduction band (CB) of TiO2 to CB of CuO and then to nearby CeO2.

Facile preparation of a V2O3/carbon fiber composite and its application for long-term performance lithium-ion batteries

In the present work, a vanadium-trioxide/carbon-nanofiber composite (V2O3/CNF), integrated with different amounts of V2O3, was synthesized by a simple approach. After a simple combined electrospinning and carbonization process, V2O3 nanoparticles were successfully distributed through carbon fibers. Due to the synergistic effect between V2O3 and carbon, V2O3/CNF as an anode of lithium-ion batteries (LIBs) exhibits high reversible capacity and excellent long-term cycling stability. The content of V2O3 is of great importance to the electrochemical performance. The V2O3/CNF with the optimized content of V2O3 (57 wt%) shows a capacity of 544 mA h g−1 at a current density of 0.5 A g−1 after 500 cycles. More importantly, a capacity of 204 mA h g−1 at a high current density of 4 A g−1 can be retained after 1000 cycles.

Selective corrosion of LaCoO3 by NaOH: structural evolution and enhanced activity for benzene oxidation

La(OH)3 nanosheets have been successfully coated on electrospun LaCoO3 nanorods using a simple and facile corrosion process, where La cations are selectively precipitated using NaOH. During the oxidation process, La(OH)3 is converted to La2O3 having a mutual effect with the spontaneously generated Co3O4 and the predominant LaCoO3 component. The performances for catalytic benzene oxidation and characterization results indicate that the alkaline treatment of electrospun LaCoO3 can improve the apparent catalytic activity because more surface adsorbed oxygen species and exposed Co3+ are generated. However, if the treatment time reaches 9 h, over-deposition of La(OH)3/La2O3 species on the surface may cause a large fraction of active Co species to be inaccessible, resulting in a lower specific activity (2.9 × 10−6 molC6H6 m−2 h−1) compared to that of untreated LaCoO3 (4.8 × 10−6 molC6H6 m−2 h−1). A treatment time of 3 h provides the highest specific activity, 1.01 × 10−5 molC6H6 m−2 h−1. Moreover, the obtained catalyst shows deactivation of only 3% benzene conversion in a stability test at 450 °C for 48 h. Therefore, NaOH-treated LaCoO3 is a promising catalyst for the practical removal of volatile organic compounds due to its high efficiency, good stability, and convenient preparation.

Electrospun BiOCl/Bi2Ti2O7 Nanorod Heterostructures with Enhanced Solar Light Efficiency in the Photocatalytic Degradation of Tetracycline Hydrochloride

Bismuth titanates (BTs) can be fabricated by electrospinning combined with calcination at different temperatures. BiOCl/Bi2Ti2O7 nanorod heterostructures were obtained at 500 °C. They possess excellent photocatalytic efficiency and stability for tetracycline hydrochloride (TC‐HCl) degradation under simulated solar light. The excellent catalytic activity is predominantly attributed to the heterostructure between BiOCl and Bi2Ti2O7, which accelerates the separation of photogenerated carriers while the narrow band gap of Bi2Ti2O7 enhances solar energy utilization. On the basis of energy band engineering, scavenger tests, and LC‐HRMS analysis, a possible degradation pathway of TC‐HCl and photocatalytic mechanism were proposed. Our work can predict a facile route for achieving high photocatalytic performance of Bi2Ti2O7‐based materials in the application of TC‐HCl degradation.