Yongjin Luo

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.

Electrospun nitrogen and carbon co-doped porous TiO2 nanofibers with high visible light photocatalytic activity

Nitrogen and carbon co-doped porous TiO2 nanofibers (NCPTNs) were exploited by a combination of electrospinning and controlled calcination technologies. Polyvinyl pyrrolidone (PVP) was employed both as a template and as a nitrogen and carbon source. It is clear that the prepared NCPTNs exhibit high absorption in the visible light region, suggesting that the co-doping of nitrogen and carbon onto TiO2 not only leads to a shift of the absorption edge to lower energy by inducing new band levels, but also creates large amounts of single-electron-trapped oxygen vacancy. Besides, the porous structure and high surface area provide large active points for the photodecomposition reaction of methylene blue. Moreover, the NCPTN obtained in 5 wt% urea shows the highest photocatalytic activity for methylene blue decomposition under the visible light irradiation.

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.

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.

Visible light-assisted efficient degradation of dye pollutants with biomass-supported TiO 2 hybrids

The objective of this work was to develop a novel organic-inorganic hybrid nanomaterial from agricultural biomass waste for environmental applications. The sugarcane bagasse (SB) supported TiO2 hybrids were firstly synthesized via a sol-gel method. A series of characterizations were carried out to reveal the structures and components of obtained hybrids. Due to organic-inorganic hybrid (OIH) effect and element doping, the SB-TiO2 hybrid can expand its optical absorbance ranging from ultraviolet to visible light. The optimal hybrid catalyst prepared with SB doping amount of 2g in 100mL titanic gel and calcined at 200°C was able to degradate 95.0% methyl orange (MO) in 5h under visible light. This study will pave a new and facile pathway for novel visible light driven photocatalysts based on TiO2 modified by agricultural biomass waste.

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.