Jinzhang Xu

In Situ Ion Exchange Synthesis of Strongly Coupled Ag@AgCl/g-C3N4 Porous Nanosheets as Plasmonic Photocatalyst for Highly Efficient Visible-Light Photocatalysis

A novel efficient Ag@AgCl/g-C3N4 plasmonic photocatalyst was synthesized by a rational in situ ion exchange approach between exfoliated g-C3N4 nanosheets with porous 2D morphology and AgNO3. The as-prepared Ag@AgCl-9/g-C3N4 plasmonic photocatalyst exhibited excellent photocatalytic performance under visible light irradiation for rhodamine B degradation with a rate constant of 0.1954 min(-1), which is ∼41.6 and ∼16.8 times higher than those of the g-C3N4 (∼0.0047 min(-1)) and Ag/AgCl (∼0.0116 min(-1)), respectively. The degradation of methylene blue, methyl orange, and colorless phenol further confirmed the broad spectrum photocatalytic degradation abilities of Ag@AgCl-9/g-C3N4. These results suggested that an integration of the synergetic effect of suitable size plasmonic Ag@AgCl and strong coupling effect between the Ag@AgCl nanoparticles and the exfoliated porous g-C3N4 nanosheets was superior for visible-light-responsive and fast separation of photogenerated electron-hole pairs, thus significantly improving the photocatalytic efficiency. This work may provide a novel concept for the rational design of stable and high performance g-C3N4-based plasmonic photocatalysts for unique photochemical reaction.

In Situ Synthesis of Water-Soluble Magnetic Graphitic Carbon Nitride Photocatalyst and Its Synergistic Catalytic Performance

Water-soluble magnetic-functionalized graphitic carbon nitride (g-C3N4) composites were synthesized successfully by in situ decorating spinel ZnFe2O4 nanoparticles on g-C3N4 sheets (CN-ZnFe) through a one-step solvothermal method. The magnetic properties of CN-ZnFe can be effectively controlled via tuning the coverage density and the size of ZnFe2O4 nanoparticles. The results indicate that the CN-ZnFe exhibits excellent photocatalytic efficiency for methyl orange (MO) and fast separation from aqueous solution by magnet. Interestingly, the catalytic performance of the CN-ZnFe is strongly dependent on the loading of ZnFe2O4. The optimum activity of 160CN-ZnFe photocatalyst is almost 6.4 and 5.6 times higher than those of individual g-C3N4 and ZnFe2O4 toward MO degradation, respectively. By carefully investigating the influence factors, a possible mechanism is proposed and it is believed that the synergistic effect of g-C3N4 and ZnFe2O4, the smaller particle size, and the high solubility in water contribute to the effective electron-hole pairs separation and excellent photocatalytic efficiency. This work could provide new insights that g-C3N4 sheets function as good support to develop highly efficient g-C3N4-based magnetic photocatalysts in environmental pollution cleanup.

Porous magnetic carbon sheets from biomass as an adsorbent for the fast removal of organic pollutants from aqueous solution

A facile and scalable in situ synthetic strategy (simultaneous template–graphitization) was developed to fabricate carbon-stabilized Fe/Fe3C nanoparticles, which were homogeneously embedded in porous carbon sheets (PMCS) as an excellent adsorbent for wastewater treatment. In the synthesis, the graphitic catalyst precursor (Fe(NO3)3) and template agent (Al(NO3)3) were introduced simultaneously into the agar hydrogel through the coordination of the metal precursor with the functional groups of agar, thus resulting in simultaneous realization of the template and graphitization of the carbon source under heat treatment. The PMCS with high surface area (1023.2 m2 g−1) exhibited high adsorption capacities and fast adsorption rates toward dyes. Using methylene blue (MB), methyl orange (MO) and crystal violet (CV) as model pollutants, the maximum adsorption capabilities for MB, MO, and CV reached 1615.9, 1062.4 and 1728.3 mg g−1, respectively. Moreover, the possibility of magnetic separation also facilitated its application in wastewater treatment on a large scale. This multifunctional material can potentially be used as a super adsorbent to efficiently remove pollutants from wastewater.

Rationally designed 1D Ag@AgVO3 nanowire/graphene/protonated g-C3N4 nanosheet heterojunctions for enhanced photocatalysis via electrostatic self-assembly and photochemical reduction methods

1D Ag@AgVO3 nanowire/graphene/protonated g-C3N4 nanosheet (Ag@AgVO3/rGO/PCN) heterojunctions are fabricated via a simple electrostatic self-assembly process followed by a photochemical reduction method. In this hybrid structure, 1D Ag@AgVO3 nanowires penetrate through 2D nanosheets (graphene and PCN), forming a 3D hybrid photocatalyst, which is applied as an efficient visible light driven photocatalyst for organic pollutant degradation. Its enhanced photocatalytic activity is ascribed to the well-known electronic conductivity of 2D graphene, the intense visible light absorption of 1D Ag@AgVO3 nanowires, large surface areas and rapid photogenerated charge interface transfer and separation. Our results provide a facile way to fabricate hierarchical g-C3N4-based photocatalysts in a controlled manner and highlight promising prospects by adopting an integrative 1D and 2D nanomaterial strategy to design more efficient semiconductor-based composite photocatalysts with high photocatalytic activities and a wide spectral response toward environmental and energy applications.

Polyaniline nanorods dotted on graphene oxide nanosheets as a novel super adsorbent for Cr(VI)

Hierarchical nanocomposites of polyaniline (PANI) nanorods array on graphene oxide (GO) nanosheets are successfully obtained by dilute polymerization under -20 °C. They exhibit excellent water treatment performance with a superb removal capacity of 1149.4 mg g(-1) for Cr(VI).

Superior adsorption capacity of hierarchical iron oxide@magnesium silicate magnetic nanorods for fast removal of organic pollutants from aqueous solution

Novel hierarchical core–shell iron oxide@magnesium silicate magnetic nanorods (HIO@MgSi) were fabricated via a versatile sol–gel process through hydrothermal reaction. They contain magnetic iron oxide (Fe3O4) cores and hierarchical shells (MgSi) made of ultrathin nanosheets (ca. 5 nm). Using methylene blue as a model compound, the HIO@MgSi nanorods showed fast adsorption kinetics and a superb adsorption capacity. 99.3% of methylene blue was adsorbed onto the surface of the HIO@MgSi nanorods in 40 min contact time. A maximum adsorption capacity of 2020.20 mg g−1 was achieved after 4 h. This study indicated that HIO@MgSi nanorods can be used as a potential super adsorbent to remove cationic organic pollutants effectively and rapidly from large volumes of industrial wastewater or drinking water.

Bandgap Engineering and Mechanism Study of Nonmetal and Metal Ion Codoped Carbon Nitride: C+Fe as an Example

Bandgap narrowing and a more positive valence band (VB) potential are generally considered to be effective methods for improving visible-light-driven photocatalysts because of the significant enhancement of visible-light absorption and oxidation ability. Herein, an approach is reported for the synthesis of a novel visible-light-driven high performance polymer photocatalyst based on band structure control and nonmetal and metal ion codoping, that is, C and Fe-codoped as a model, by a simple thermal conversion method. The results indicate that compared to pristine graphitic carbon nitride (g-C3 N4 ), C+Fe-codoped g-C3 N4 shows a narrower bandgap and remarkable positively shifted VB; as a result the light-absorption range was expanded and the oxidation capability was increased. Experimental results show that the catalytic efficiency of C+Fe-codoped g-C3 N4 for photodegradation of rhodamine B (RhB) increased 14 times, compared with pristine g-C3 N4 under visible-light absorption at λ>420 nm. The synergistic enhancement in C+Fe-codoped g-C3 N4 photocatalyst could be attributed to the following features: 1) C+Fe-codoping of g-C3 N4 tuned the bandgap and improved visible-light absorption; 2) the porous lamellar structure and decreased particle size could provide a high surface area and greatly improve photogenerated charge separation and electron transfer; and 3) both increased electrical conductivity and a more positive VB ensured the superior electron-transport property and high oxidation capability. The results imply that a high-performance photocatalyst can be obtained by combining bandgap control and doping modification; this may provide a basic concept for the rational design of high performance polymer photocatalysts with reasonable electronic structures for unique photochemical reaction.

Magnetic Fe3O4@NiO hierarchical structures: preparation and their excellent As(V) and Cr(VI) removal capabilities

Uniform three-dimensional (3D) flowerlike Fe3O4@NiO hierarchical architectures were synthesized by a simple and direct solvothermal route without any linker shell. The shell thickness and hierarchical structure of the microspheres can be tuned by adjusting the reaction duration. The size of the hierarchical microspheres is 250–300 nm and the shell is composed of several nanoflakes with a thickness of 20–30 nm and a width of 50–60 nm. The microspheres possess high specific surface area of 125.63 m2 g−1 and high saturation magnetization, which allows them to have strong removal ability and are easily separated from solution by magnetic separation method. The microspheres are applied as adsorbents for As(V) and Cr(VI) ions removal from wastewater, and exhibit a high adsorption capacity with an adsorption capacity of ∼117.6 mg g−1 for As(V) and 184.2 mg g−1 for Cr(VI), which is mainly attributed to the large specific surface area and hierarchical structures of Fe3O4@NiO hierarchical microspheres. This work provides a promising approach for the design and synthesis of multifunctional microspheres, which can be used for water treatment, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors.

Fabrication of Fe/Fe3C@porous carbon sheets from biomass and their application for simultaneous reduction and adsorption of uranium(VI) from solution

Carbon-encapsulated Fe/Fe3C nanoparticles embedded in porous carbon sheets (Fe/Fe3C@PCS) were fabricated by a one step carbothermic reduction, using natural abundant biomass derivatives. Batch experimental results showed that Fe/Fe3C@PCS could effectively remove the radionuclide U(VI) from simulated wastewater in the presence of carbonate or calcium under laboratory conditions with reduced cost, improved activity and enhanced kinetics. Compared with activated carbon (AC), Fe/Fe3C@PCS is more efficient, and can remove U(VI) quantitatively at an initial concentration of up to 140 mg L−1. The major reaction pathway involved the reduction of U(VI) to the insoluble U(IV) species as identified by X-ray photoelectron spectroscopy (XPS) analysis. This study demonstrated the potential application of Fe/Fe3C@PCS as a low cost and effective remediation strategy for U-contaminated wastewater cleanup.

Influence of deposition strategies on CdSe quantum dot-sensitized solar cells: a comparison between successive ionic layer adsorption and reaction and chemical bath deposition

Deposition and synthesis strategies of quantum dots (QDs) exert appreciable influences on the photovoltaic properties of quantum dot-sensitized solar cells (QDSCs). In this paper, a systematic characterization of morphology, optical and electrochemical properties has been carried out to correlate the assembling of QDs with the performance of the resultant QDSCs. CdSe sensitized TiO2 solar cells were investigated focusing on the influences of two commonly used in situ QD deposition methods, i.e., successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD). By applying a pre-assembled CdS seed layer prior to CdSe deposition, a power conversion efficiency up to 4.85% has been achieved for CdS/CBD-CdSe cells, which is appreciably higher than 3.89% for the CdS/SILAR-CdSe cell. TEM images revealed that CdS seeded SILAR is only capable of less than full coverage, in contrast, the CdS seeded CBD technique secures full conformal coverage of QDs on TiO2. The full conformal coverage of QDs offers two benefits, (1) high loading of QDs for efficient photon capturing, contributing to the increase of photocurrent, and (2) suppression of interfacial charge recombination, resulting in high open-circuit voltage and a large fill factor. Our success in achieving the perfect coverage of QDs based on CdS seeded CBD highlights strong implications for the performance optimization of QDSCs.