Xinsheng Zheng

Facile Synthesis of Carbon-Coated Spinel Li4Ti5O12/Rutile-TiO2 Composites as an Improved Anode Material in Full Lithium-Ion Batteries with LiFePO4@N-Doped Carbon Cathode

The spinel Li4Ti5O12/rutile-TiO2@carbon (LTO-RTO@C) composites were fabricated via a hydrothermal method combined with calcination treatment employing glucose as carbon source. The carbon coating layer and the in situ formed rutile-TiO2 can effectively enhance the electric conductivity and provide quick Li+ diffusion pathways for Li4Ti5O12. When used as an anode material for lithium-ion batteries, the rate capability and cycling stability of LTO-RTO@C composites were improved in comparison with those of pure Li4Ti5O12 or Li4Ti5O12/rutile-TiO2. Moreover, the potential of approximately 1.8 V rechargeable full lithium-ion batteries has been achieved by utilizing an LTO-RTO@C anode and a LiFePO4@N-doped carbon cathode.

Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources

Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO4 to obtain LiFePO4@nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO4 particles can effectively enhance the electrical conductivity and provide fast Li+ transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO4) exhibits a favorable rate performance and stable cycling performance.

Co nanoparticles/Co, N, S tri-doped graphene templated from in-situ formed Co, S co-doped g-C3N4 as an active bifunctional electrocatalyst for overall water splitting

The development of high-performance electrocatalyst with earth-abundant elements for water-splitting is a key factor to improve its cost efficiency. Herein, a noble metal-free bifunctional electrocatalyst was synthesized by a facile pyrolysis method using sucrose, urea, Co(NO3)2 and sulfur powder as raw materials. During the fabrication process, Co, S co-doped graphitic carbon nitride (g-C3N4) was first produced, and then this in-situ-formed template further induced the generation of a Co, N, S tri-doped graphene coupled with Co nanoparticles (NPs) in the following pyrolysis process. The effect of pyrolysis temperature (700, 800, and 900 °C) on the physical properties and electrochemical performances of the final product was studied. Thanks to the increased number of graphene layer encapsulated Co NPs, higher graphitization degree of carbon matrix and the existence of hierarchical macro/meso pores, the composite electrocatalyst prepared under 900 °C presented the best activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with outstanding long-term durability. This work presented a facile method for the fabrication of non-noble-metal-based carbon composite from in-situ-formed template and also demonstrated a potential bifunctional electrocatalyst for the future investigation and application.

Basophilic green fluorescent carbon nanoparticles derived from benzoxazine for the detection of Cr(VI) in a strongly alkaline environment

Fluorescent probes for heavy or transition metal ions in extreme environments are crucially important for practical use. In this work, basophilic green fluorescent carbon nanoparticles (G-CNPs) were synthesized by one-pot hydrothermal treatment of benzoxazine in NaOH aqueous solution. These G-CNPs showed favorable dispersibility in strongly alkaline conditions due to the abundant functional groups on their surface. Based on their good photoluminescence properties and excellent stability, the G-CNPs could be used to detect Cr(VI) in a strongly alkaline environment (pH = 14) through a fluorescence quenching effect. This detection process was achieved selectively among 17 anions within 30 seconds and the limitation was 0.58 μM (S/N = 3). It was revealed that the fluorescence turn-off process was caused by the inner filter effect (IFE) of Cr(VI). This study developed efficient fluorescence sensors based on fluorescent carbon nanoparticles, which could be used in strongly alkaline environments.

Synthesis of core–shell structured Ag3PO4@benzoxazine soft gel nanocomposites and their photocatalytic performance

In the investigation of photocatalysis, it remains a significant challenge to improve the interface properties and enhance the stability of photocatalysts. To address this challenge, we have prepared core–shell structured Ag3PO4@benzoxazine soft gel nanocomposites, in which Ag3PO4 nanoparticles are coated with uniform benzoxazine monomers via a facile solution self-assembly method. The benzoxazine monomers are attached to the surface of Ag3PO4 nanoparticles by coordination interaction between the amino group of the benzoxazine monomers and Ag+ ions on the surface of Ag3PO4, and the soft gel shell is formed via the interaction of hydrogen bonds between the benzoxazine monomers. The nanocomposites exhibit higher visible-light photocatalytic stability than the bare Ag3PO4 nanoparticles under the same reaction conditions. Both experimental evidence and electrochemical calculations reveal that the high photocatalytic stability of Ag3PO4@benzoxazine soft gel nanocomposites mainly originates from the silver amine complex ion formed in the interface between the core and the shell. The integration of photocatalysts with the advantages of soft gels can provide a new way to improve the interface properties of Ag3PO4 catalyst and facilitate the realization of the long-standing goal of performing chemical synthesis using sunlight.

A green approach for the synthesis of novel Ag3PO4/SnO2/porcine bone and its exploitation as a catalyst in the photodegradation of lignosulfonate into alkyl acids

A novel Ag3PO4/SnO2/porcine bone composite photocatalyst was successfully prepared via an ion exchange method, which can convert lignin derivatives into small molecular acids upon exposure to visible light at room temperature at ambient pressure. The composition characterization, optical absorption properties and photocatalytic activities of the Ag3PO4/SnO2/porcine bone composites were thoroughly investigated. The certain role of each component of the composites in the degradation reaction was discussed: Ag3PO4 acted as the major active component, while SnO2 and porcine bone as cocatalyst contributed to improve the photocatalytic activity and stability of Ag3PO4. The enhanced activity of the Ag3PO4/SnO2/porcine bone composite may be attributed to the synergistic effect including the matched energy band structures of Ag3PO4 and SnO2 for the decrease in the probability of electron–hole recombination and improved performance in the presence of hierarchical porous porcine bone (hydroxyapatite). This paper also analyzed the change of the molecular weight and structure of sodium lignin sulfonate in the photocatalytic reaction and discussed the possible photocatalytic mechanism of the photocatalyst composite, indicating that the benzene rings of guaiacol were oxidized into different alkyl acids (maleic acid, oxalic acid, formic acid and methoxy acetic acid).

pH controlled green luminescent carbon dots derived from benzoxazine monomers for the fluorescence turn-on and turn-off detection

Emerging carbon dots (CDs) are widely used as fluorescent probes in biological and environmental fields, nevertheless, the control of CDs based on different detection mechanisms is rarely reported. In this paper, green luminescent CDs (G-CDs) were prepared by a facile hydrothermal treatment of benzoxazine monomers (BZM). The obtained G-CDs showed pH dependent photoluminescence, which could be designed as fluorescence turn-on and turn-off sensors. The G-CDs exhibited weak photoluminescence at pH = 7.0 and could be turned on by Zn(II) selectively with the limitation of 0.32 μM in the concentration range from 1 to 100 μM. When pH = 10.0, Cr(VI) could quench the strong fluorescence of G-CDs efficiently, and the limit of detection was 0.99 μM with a linear range of 1-50 μM. Furthermore, the fluorescence turn-on and turn-off performance of G-CDs was attributed to the intramolecular charge transfer (ICT) of Zn(II) and the inner filter effect (IFE) of Cr(VI), respectively. The excellent probes were successfully applied for the detection of Zn(II) in biological system and Cr(VI) in environment.

Regulation of interfacial properties of polybenzoxazine for effective removal of Cr(VI) from aqueous solution

A novel polybenzoxazine for effective removal of Cr(VI) from aqueous solution has been fabricated by using inexpensive CuCl2–melamine complex, bisphenol A and formaldehyde. In the curing process of benzoxazine monomer, different curing media can guide the directional distribution of functional groups of different polarity in the benzoxazine monomer, and thus can achieve the effect of regulating the interfacial properties of polybenzoxazine, and achieved an amine-rich surface and a suitable surface morphology by changing the monomer structure and the ratio of raw materials. This novel polybenzoxazine sorbent was characterized by using high-resolution scanning electron microscopy, energy dispersive spectrometer, Fourier transform infrared spectroscopy and thermogravimetric analysis. The experimental maximum removal efficiency for Cr(VI) was up to 96.7% and adsorption capacity was 116.32 mg/g at solution pH of 2 with temperature of 25°C. Langmuir model was successfully fitted with various curves obtained at different temperatures, and the kinetic data were well described by pseudo-second-order model. The novel polybenzoxazine absorbent promises such advantages as high removal efficiency, low cost, facile fabrication and good recycling performance.

Application of the correct design of successive self-nucleation and annealing (SSA) to study the stereo-defects and its distribution of homo- and co-polypropylene

The stereo-defects and its distribution of four homo- and co-polypropylene samples with different processing properties were studied through the correct design Successive Self-Nucleation and Annealing (SSA), and other characterization methods such as Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), Temperature Rising Elution Fractionation (TREF), respectively. Firstly, the preliminary characterization found that the two homo-polypropylene or co-polypropylene samples had the similar mechanical and thermal properties, and the SSA results also revealed the internal microstructure of the different kind of polypropylene was almost exactly the same, representing the alike isotactic sequence length, the fractions weight of the isotactic sequence, and the isotactic sequence length distribution of the same kind of polypropylene. Compared with the homo-polypropylene, the DSC, GPC, and TREF tests indicated there were difference in the properties of the co-polypropylene samples, revealing the disparities in molecular chain microstructure. The SSA results after the correct Ts for each sample showed there were obvious differences in the (statistical) lamellar thickness and its distribution and the fractions weight of different fractions after SSA treatment, further revealing the microstructure difference on the isotactic sequence length, and the isotactic sequence length distribution of homo- and co-polypropylene samples. Besides, the correct design SSA also indicated the polar copolymer monomer had a great influence on the high isotactic component in co-polypropylene microstructure.