Xinfei Fan
Dalian University of Technology
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Featured researches published by Xinfei Fan.
Environmental Science & Technology | 2011
Hui Zhang; Xinfei Fan; Xie Quan; Shuo Chen; Hongtao Yu
Interfacing photocatalyst with graphene sheet gives rise to an extraordinary modification to the properties of the resulting hybrids. Graphene sheet grafted Ag@AgCl composite is fabricated by photoreducing AgCl/graphene oxide (GO) hybrids prepared by deposition-precipitation method. The microscopic analysis and Raman scattering reveal the direct interface between Ag nanocrystal and graphene sheet, which manipulates the electronic structures of Ag@AgCl. UV-vis absorption spectra of Ag@AgCl/reduced GO (RGO) hybrids exhibit strong absorbance in the visible region due to the surface plasmon resonance (SPR) absorption of Ag nanocrystal. In situ assembled Ag@AgCl/RGO plasmonic photocatalyst exhibits remarkable photocatalytic activity. Compared with bare Ag@AgCl nanoparticle, a 4-fold enhancement in the photodegradation rate toward rhodamine B is observed over Ag@AgCl/RGO hybrids under visible light irradiation. The large enhancement of photocatalytic activity was attributed to the effective charge transfer from plasmon-excited Ag nanocrystal to RGO, which suppress the charge recombination during photocatalytic process. This work could provide new insights into the fabrication of high performance plasmonic photocatalyst and facilitate their practical application in environmental issues.
Angewandte Chemie | 2015
Yanming Liu; Xie Quan; Xinfei Fan; Hua Wang; Shuo Chen
H2O2 production by electroreduction of O2 is an attractive alternative to the current anthraquinone process, which is highly desirable for chemical industries and environmental remediation. However, it remains a great challenge to develop cost-effective electrocatalysts for H2O2 synthesis. Here, hierarchically porous carbon (HPC) was proposed for the electrosynthesis of H2O2 from O2 reduction. It exhibited high activity for O2 reduction and good H2O2 selectivity (95.0-70.2%, most of them >90.0% at pH 1-4 and >80.0% at pH 7). High-yield H2O2 generation has been achieved on HPC with H2O2 concentrations of 222.6-62.0 mmol L(-1) (2.5 h) and corresponding H2O2 production rates of 395.7-110.2 mmol h(-1) g(-1) at pH 1-7 and -0.5 V. Moreover, HPC was energy-efficient for H2O2 production with current efficiency of 81.8-70.8%. The exceptional performance of HPC for electrosynthesis of H2O2 could be attributed to its high content of sp(3)-C and defects, large surface area and fast mass transfer.
Angewandte Chemie | 2010
Hongtao Yu; Shuo Chen; Xinfei Fan; Xie Quan; Huimin Zhao; Xinyong Li; Yaobin Zhang
Improvement of conversion efficiency of solar energy to electricity or chemical energy has attracted extensive attention due to the increasing need for clean and renewable energy. Silicon has successfully been applied in photoelectric conversion, but it is difficult to employ Si in converting solar energy to chemical energy due to rapid formation of an insulating oxide layer. This problem could be overcome by coating the surface of Si with a transparent charge collector serving as a protective layer. Noble metals, wide-gap semiconductors, and polymer films were commonly employed as protective layers. The high price (noble metal), relatively low conductivity (wide-gap semiconductor), and limited thermal and chemical stability (polymer) restricted practical application of these materials in conversion of solar to chemical energy. Graphene (Gr), discovered in 2004, is a promising protective material due to its good stability, extremely high electron mobility, and excellent optical transparency. Moreover, Gr is an ideal two-dimensional ultrathin material with comparatively fewer defects than film constructed from nanoparticles. Thus, it is a favorable material for charge transfer. In fact, Gr has found applications as the electron acceptor in dye-sensitized solar cells and polymer solar cells. However, no work has been reported Gr protective layers. We have now built a macroporous Si (MPSi)/Gr heterojunction by depositing Gr on the surface of MPSi and demonstrated that Gr can be used as protective layer for MPSi to improve its ability to convert solar to chemical energy. Macroporous Si was selected as the substrate because it can offer higher surface area and lower reflection than planar Si wafer. The MPSi was fabricated by chemically etching p-type Si wafer ((100) orientation, 3–4 Wcm resistivity). The etching electrolyte was composed of 5m NH4F and 0.02m AgNO3. Graphene was obtained in two steps: fabricating graphite oxides by the Hummer method, and then reducing them to Gr by pyrolysis at 1050 8C. To deposit Gr on the surface of MPSi, an MPSi cathode was immersed in a Gr suspension, and electrophoresis was performed. The stable Gr suspension was composed of 0.01 g of Gr, 100 mL of isopropyl alcohol, and 0.005 g of Mg(NO3)2·6H2O, [13] and the applied voltage and deposition duration of electrophoresis were 160 V and 10 s, respectively. After electrophoresis, annealing was carried out to improve the adhesion between the Gr layer and MPSi. As shown in Figure 1 a, the longest part of the as-prepared Gr sheets is shorter than 2 mm, and ripples can be observed. The typical thicknesses of the ripples were measured from different sections marked by the rectangular frames in Figure 1b. According to their line profiles, the average thickness of the ripples is 2.35 nm, which indicates that the sample as prepared is few-layer Gr (4–6 layers). According to Liu et al. , few-layer Gr is less reactive but more stable than monolayer Gr in aqueous solution. Therefore, few-layer Gr is a suitable choice as protective layer.
Water Research | 2010
Ning Ma; Yaobin Zhang; Xie Quan; Xinfei Fan; Huimin Zhao
Membrane filtration has been increasingly used for water treatment and wastewater reclamation in recent years. To further improve the effectiveness of membrane process and reduce membrane fouling, a highly reactive photocatalytic membrane, Ag-TiO(2)/hydroxiapiate (HAP, Ca(10)(PO(4))(6)(OH)(2))/Al(2)O(3), was employed to realize microfiltration (MF) coupling photocatalysis for surface water treatment. The effectiveness on the potential of membrane was investigated by removing humic acid (HA) test under different feed total organic carbon (TOC), light intensity and transmembrane pressure (TMP). The HA removal and anti-fouling property of as-prepared membrane was improved under UV irradiation, likely due to photocatalytic degradation of foulants along with filtration simultaneously. Under given feed water composition, increasing the light intensity resulted in increased removal of HA from aqueous solution. However, a limiting TMP seems to exist beyond which the increased HA removal cannot be sustained. Fouling behavior analysis indicated that the transition in fouling mode from initial pore blocking to cake filtration occurred much slower as UV irradiated. Furthermore, a superior efficiency on removal of trace organic contaminants, as well as milder flux reduction, was presented from surface water treatment, which demonstrated that the integrated system with enhanced performance is foreseen as an emerging technique for water treatment.
Journal of Colloid and Interface Science | 2015
Xiaona Li; Shuo Chen; Xinfei Fan; Xie Quan; Feng Tan; Yaobin Zhang; Jinsuo Gao
Carbon nanofibers (CNFs) were prepared by electrospun polyacrylonitrile (PAN) polymer solutions followed by thermal treatment. For the first time, the influence of stabilization procedure on the structure properties of CNFs was explored to improve the adsorption capacity of CNFs towards the environmental pollutants from aqueous solution. The adsorption of three organic chemicals including ciprofloxacin (CIP), bisphenol (BPA) and 2-chlorophenol (2-CP) on electrospun CNFs with high surface area of 2326m(2)/g and micro/mesoporous structure characteristics were investigated. The adsorption affinities were compared with that of the commercial powder activated carbon (PAC). The adsorption kinetics and isotherms showed that the maximum adsorption capacities (qm) of CNFs towards the three pollutants are sequenced in the order of CIP>BPA>2-CP, which are 2.6-fold (CIP), 1.6-fold (BPA) and 1.1-fold (2-CP) increase respectively in comparison with that of PAC adsorption. It was assumed that the micro/mesoporous structure of CNFs, molecular size of the pollutants and the π electron interaction play important roles on the high adsorption capacity exhibited by CNFs. In addition, electrostatic interaction and hydrophobic interaction also contribute to the adsorption of CNFs. This study demonstrates that the electrospun CNFs are promising adsorbents for the removal of pollutants from aqueous solutions.
Environmental Science & Technology | 2015
Xinfei Fan; Huimin Zhao; Yanming Liu; Xie Quan; Hongtao Yu; Shuo Chen
Membrane filtration provides effective solutions for removing contaminants, but achieving high permeability, good selectivity, and antifouling ability remains a great challenge for existing membrane filtration technologies. In this work, membrane filtration coupled with electrochemistry has been developed to enhance the filtration performance of a CNTs/Al2O3 membrane. The as-prepared CNTs/Al2O3 membrane, obtained by coating interconnected CNTs on an Al2O3 substrate, presented good pore-size tunability, mechanical stability, and electroconductivity. For the removal of a target (silica spheres as a probe) with a size comparable to the membrane pore size, the removal efficiency and flux at +1.5 V were 1.1 and 1.5 times higher, respectively, than those without electrochemical assistance. Moreover, the membrane also exhibited a greatly enhanced removal efficiency for contaminants smaller than the membrane pores, providing enhancements of 4 orders of magnitude and a factor of 5.7 for latex particles and phenol, respectively. These results indicated that both the permeability and the selectivity of CNTs/Al2O3 membranes can be significantly improved by electrochemical assistance, which was further confirmed by the removal of natural organic matter (NOM). The permeate flux and NOM removal efficiency at +1.5 V were about 1.6 and 3.0 times higher, respectively, than those without electrochemical assistance. In addition, the lost flux of the fouled membrane was almost completely recovered by an electrochemically assisted backwashing process.
Environmental Science & Technology | 2014
Gaoliang Wei; Hongtao Yu; Xie Quan; Shuo Chen; Huimin Zhao; Xinfei Fan
Manipulating carbon nanotubes (CNTs) through engineering into advanced membranes with superior performance for disinfection and decontamination of water shows great promise but is challenging. In this paper, a facile assembly of CNTs into novel hollow fiber membranes with tunable inner/outer diameters and structures is developed for the first time. These free-standing membranes composed entirely of CNTs feature a porosity of 86±5% and a permeation flux of about 460±50 L m(-2) h(-1) at a pressure differential of 0.04 MPa across the membrane. The randomly oriented interwoven structure of CNTs endows the membranes considerable resistance to pore blockage. Moreover, the adsorption capability of the CNT hollow fiber membranes, which is crucial in the efficient removal of small and trace contaminant molecules, is about 2 orders of magnitude higher than that of commercial polyvinylidene fluoride hollow fiber membranes. The unique advantage of the CNT hollow fiber membranes over other commercial membranes is that they can be in situ electrochemically regenerated after adsorption saturation.
Chinese Journal of Catalysis | 2012
Huimin Zhao; Fang Su; Xinfei Fan; Hongtao Yu; Dan Wu; Xie Quan
Abstract Here we used a hydrothermal process and calcination in the absence of O2 to obtain a highly efficient chemically bonded graphene-TiO2 nanocomposite photocatalyst utilizing graphene oxide and tetra-n-butyl titanate as precursors. The nanocomposite photocatalyst could inhibit the recombination of photo-generated electron-hole pairs of TiO2 and then enhanced the photocatalytic efficiency. The results presented by transmission electron microscope, X-ray diffraction, Raman microscopy, and X-ray photoelectron spectroscopy showed that anatase TiO2 particles attached on the surface of the film-shaped graphene. The photocatalytic capability of graphene-TiO2 catalyst under UV light was evaluated and the results showed that graphene-TiO2 had good stability and better photocatalytic ability than pure TiO2 prepared by similar method. The holes governed the photocatalytic process and the photocatalytic performance of this photocatalyst was improved at high pH value.
Angewandte Chemie | 2017
Yanming Liu; Zhang Yb; Kai Chen; Xie Quan; Xinfei Fan; Yan Su; Shuo Chen; Huimin Zhao; Yaobin Zhang; Hongtao Yu; Michael R. Hoffmann
Electrochemical reduction of CO2 to ethanol, a clean and renewable liquid fuel with high heating value, is an attractive strategy for global warming mitigation and resource utilization. However, converting CO2 to ethanol remains great challenge due to the low activity, poor product selectivity and stability of electrocatalysts. Here, the B- and N-co-doped nanodiamond (BND) was reported as an efficient and stable electrode for selective reduction of CO2 to ethanol. Good ethanol selectivity was achieved on the BND with high Faradaic efficiency of 93.2 % (-1.0 V vs. RHE), which overcame the limitation of low selectivity for multicarbon or high heating value fuels. Its superior performance was mainly originated from the synergistic effect of B and N co-doping, high N content and overpotential for hydrogen evolution. The possible pathway for CO2 reduction revealed by DFT computation was CO2 →*COOH→*CO→*COCO→*COCH2 OH→*CH2 OCH2 OH→CH3 CH2 OH.
RSC Advances | 2016
Qi Zhang; Xinfei Fan; Hua Wang; Shuo Chen; Xie Quan
Catalytic membranes have an extensive range of desirable applications in chemical fields. Here, an Au-coated carbon nanotube (Au/CNT) hollow fiber membrane was fabricated by depositing Au nanoparticles on a CNT hollow fiber membrane. The Au/CNT hollow fiber membrane exhibited excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol. The observed improvement in the catalytic activity can be ascribed to the synergistic effect between the Au nanoparticles and CNT membrane. The Au/CNT hollow fiber membrane described in this paper presented high stability in the 4-nitrophenol reduction process. This study offers a new avenue for the exploration of membranes for practical applications.