Table of Content
05 June 2020, Volume 71 Issue 6
Reviews and monographs
Research progress of solvent-in-salt electrolyte for supercapacitor
Le YANG, Jinhe YU, Rong FU, Yuanyang XIE, Chang YU, Jieshan QIU
2020, 71(6):  2457-2465.  doi:10.11949/0438-1157.20191530
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Solvent-in-salt(SIS), as a new type of electrolyte, is highly concerned, where the electrolyte ions and solvent form a special solvated structure to passivate solvent and further inhibit solvent decomposition/polarization as well as reduce its reactivity. Benefiting from these characteristics including well electrochemical stability, wide work voltage window, SIS features unique and superior merits in supercapacitor, offering prospects of unprecedented advances in device performance. This article focuses on the principles and advantages of SIS-type electrolytes, combs the research progress of SIS as an electrolyte for supercapacitors in recent years, summarizes its existing problems, and looks forward to the future development direction of SIS-type electrolyte.

Progress of carbon-based micro-/nanostructured hollow electrocatalysts for water splitting
Tongzhen TIAN, Nianwu LI, Le YU
2020, 71(6):  2466-2480.  doi:10.11949/0438-1157.20200145
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The clean and high energy density characteristics of hydrogen energy make it an ideal energy source for the future. Electrocatalysts are indispensable elements for large-scale water electrolysis, which can efficiently accelerate electrochemical reactions occurring at both ends. Benefitting from high specific surface area, well-defined void space and tuneable chemical compositions, hollow nanostructures of carbon based nanomaterials could be applied as promising candidates of direct electrocatalysts or supports for loading internal or external catalysts. Herein, we summarize the recent progress in the structural design of carbon-based micro-/nanostructured hollow materials as advanced catalysts for water splitting. Besides, we present the future research directions of carbon based hollow electrocatalysts for water splitting based on our personal perspectives.

Research progress on electrocatalytic nitrogen reduction reaction catalysts for ammonia synthesis
Muyun ZHENG, Yuchi WAN, Ruitao LYU
2020, 71(6):  2481-2491.  doi:10.11949/0438-1157.20200129
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Ammonia is an important chemical raw material in textiles, pharmaceuticals, fertilizers and other fields. It is also a clean energy carrier with a large demand. At present, the industrial production of ammonia is mainly based on the Haber-Bosch method, which is running at strict reaction conditions with high energy consumption and high carbon emissions. Electrocatalytic nitrogen reduction reaction (NRR) is a very promising method for ammonia synthesis at ambient temperature and pressure. Moreover, the working potential of electrocatalytic NRR is low and can be driven by electric power generated by clean energy sources. However, the current ammonia production rate and Faradaic efficiency of electrocatalytic NRR materials are low, the working stability is not high enough, the quantitative detection of trace ammonia in solution is difficult, and the detection standards are not uniform, which have brought great challenges to its development. In this review article, the electrocatalytic NRR mechanism and common research methods are firstly introduced, and then the latest research progress since 2019 on NRR catalytic materials are summarized. Finally, the challenges ahead and future perspectives in electrocatalytic NRR research are proposed.

Recent advances in porous carbon-based carbon dioxide electrocatalytic materials
Lingyu DONG, Rui GE, Yafei YUAN, Songyuan TANG, Guangping HAO, Anhui LU
2020, 71(6):  2492-2509.  doi:10.11949/0438-1157.20200106
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Electrocatalytic conversion of carbon dioxide (CO2) has attracted widespread attention. In this field, the development of precious metal-free, porous carbon-based electrocatalysts stands out being the research hot spot. First, the key parameters in terms of pore structure, surface chemistry as well as morphology of porous carbon-based electrocatalysts have been overviewed. Then, the methods to improve the porous carbon-based electrocatalysts activity are summarized. Subsequently, the nature and distribution of active centers of carbon-based electrocatalysts are discussed. In the following, the pathways to increase the density of active sites in porous carbon-based electrocatalysts are analyzed. Finally, based on the advances made in the research community in recent years, we made perspectives on the developing trend and challenges of porous carbon-based electrocatalysts for efficient CO2 electroreduction.

Applications of fullerene materials in perovskite solar cells
Xiaoqin YE, Zhiyue WEN, Wangqiang SHEN, Xing LU
2020, 71(6):  2510-2529.  doi:10.11949/0438-1157.20200084
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Since the emergence of organic-inorganic hybrid perovskite solar cells in 2009, after just over ten years of development, the photoelectric conversion efficiency has increased to more than 24%, which has attracted widespread attention. Due to their advantages of high electron mobility, adjustable energy levels and low temperature process for film-forming, fullerene materials can serve as electron transport layers (ETLs), additives in the perovskite layer, interfacial modification layers, and can even be employed in hole transport layer (HTLs) of PSCs, all of which improve efficiency and stability of the device, and also reduce hysteretic behavior. In this paper, the applications of fullerene materials in different layers of PSCs are systematically reviewed. And the basic rules of device performance improvement by decorating the structure of fullerene materials are also summed up. All these results are of great significance to promote the application of fullerene materials in perovskite solar cells.

Research progress of carbon cathode materials for Li-ion capacitors
Tao HU, Xiong ZHANG, Yabin AN, Chen LI, Yanwei MA
2020, 71(6):  2530-2546.  doi:10.11949/0438-1157.20200338
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Lithium ion capacitor is a kind of energy storage device assembled with capacitive positive electrode material and battery negative electrode material. It combines the advantages of both lithium ion battery and super capacitor, and has high energy density, high power density and long cycle life. However, due to the unbalanced capacity and kinetic imbalance between the anode and cathode, the electrochemical performance of lithium-ion capacitors is greatly limited. Generally, the power density of lithium-ion capacitors depends on the negative electrode material, while the energy density depends on the positive electrode material. Therefore, to improve the energy density of lithium-ion capacitors, it is necessary to develop the positive electrode material with high specific capacity and high conductivity. At present, carbon material is a potential electrode material because of its low cost, wide source, high specific surface area and rich pore structure. In this paper, the electrochemical properties, advantages and disadvantages of various carbon materials (including activated carbon, template carbon, graphene and biochar, etc.) as cathode materials for lithium-ion capacitors are reviewed and analyzed. Finally, suggestions and prospects for the research of cathode materials for lithium-ion capacitors are put forward.

Progress of microfluidic synthesis of metal/covalent organic frameworks
Yun ZHAO, Zhonghua XIANG
2020, 71(6):  2547-2563.  doi:10.11949/0438-1157.20200105
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Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) represent exciting porous materials, which are ingeniously constructed with diverse building blocks via coordination or covalent bonds. The bottom-up synthetic method enables to construct the desired microstructures by designing or selecting suitable building blocks. The well-defined crystalline porous structures and easy functionalized skeleton have offered MOFs and COFs superior potential application in gas storage, separation, catalysis and chemical sensing, etc. However, the conventional synthesis method of MOFs and COFs are generally conducted with autoclave or reflux in batch condition, which always results in long reaction time, inconvenient control of microstructures, inhomogeneous products and tedious operation. In recent years, the characteristics of continuous operation, precise controllability, high transfer efficiency and high repeatability of microfluidic technology have demonstrated unprecedented advantages in the field of nanomaterial preparation. This review summarized the progress of microfluidic synthesis of MOFs and COFs. The process intensification of MOFs and COFs synthesis by utilizing microfluidic technology has been reviewed. Moreover, the microstructure modification by microfluidic technology is also emphasized.

Catalytic reaction system for controllable synthesis of graphene with chemical vapor deposition
Yan JIN, Qian YANG, Wenbin ZHAO, Baoshan HU
2020, 71(6):  2564-2585.  doi:10.11949/0438-1157.20200107
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The preparation of graphene by chemical vapor deposition (CVD) is a complex heterogeneous catalytic reaction process. It is of great significance to elucidate the scientific blueprint depicting this process in the viewpoint of catalysis engineering for deliberately structural control, standardization and application of graphene-based materials. Emphasizing on the recent research advance theoretically and experimentally, this review demonstrates how carbon precursors, reactive gases, catalytic metal substrates and carbon impurities are involved in the process, and reactive carbon-containing intermediates influence the graphene growth dynamics, as well as the macro- and micro- structural attributes (e.g., layer number, quality, shape, domain structure, etc.) of as-synthesized graphene. The motivation is to figure out the regulation principles for controllable preparation of graphene through excavating general scientific laws beneath the differentiated conclusions all over the research community. Additionally, several enhanced CVD approaches are introduced briefly, and essential roles of elementary reaction steps and reactive carbon-containing intermediates played in the controllable graphene synthesis are emphatically proposed. The knowledge is firmly contributable to define the controllable preparation of large-area graphene and its derived structure appealing to defect-free, super-clean, low-price, high-speed, and mass-scale advances.

Hierarchical porous carbon materials: structure design, functional modification and new energy devices applications
Xidong LIN, Youchen TANG, Quanfei SU, Shaohong LIU, Dingcai WU
2020, 71(6):  2586-2598.  doi:10.11949/0438-1157.20200226
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The development of electrochemical energy storage and conversion technology is a long-term significant demand in China. As a key material in electrochemical energy devices, porous carbon materials have become a hot research topic in the field of energy materials and chemical engineering. Hierarchical porous carbon materials are regarded as a new class of porous carbon materials, which contain micro-, and meso-/macropores with different sizes and functions. Researchers have controllably designed and synthesized a series of novel hierarchical porous carbon materials and their composites, which possess various pore structures, pore skeletons, surface chemical properties and micro/nano-topologies. Moreover, the electrochemical performance of these emerging materials in energy storage and conversion applications has been significantly enhanced. This review summarizes the recent progress on structure design and controllable synthesis of hierarchical porous carbon materials, as well as their applications in the electrochemical energy devices. Furthermore, suggestions and prospects for their future development are presented.

Research progress of strengthening methods in graphene preparation by supercritical CO2 exfoliation
Wang YANG, Yun LI, Xiaojuan TIAN, Fan YANG, Yongfeng LI
2020, 71(6):  2599-2611.  doi:10.11949/0438-1157.20200230
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Graphene has attracted extensive attention in many fields because of its unique two-dimensional structure and excellent physical properties. The preparation of high-quality graphene is the premise of realizing its application value. Although there are many preparation methods for graphene, the development of green, low-cost and large-scale preparation strategy is still full of challenges. Highly crystalline graphene nanosheets can be obtained through the exfoliation of graphite using physical methods. Due to the advantages of cheap, green, stable, easily separated and reusable, the supercritical CO2 fluid exhibits a great potential in the preparation of graphene. Focusing on the preparation methods, the research progress in recent years about the preparation of graphene by using supercritical CO2 method has been reviewed. Especially, the employed process intensification technique has been highlighted in this field. This review can provide insights for the high-efficiency conversion of graphite into high-yield graphene in future.

Metal-organic frameworks-derived zero-dimensional materials for supercapacitors
Shuang ZONG, Xinying LIU, Aibing CHEN
2020, 71(6):  2612-2627.  doi:10.11949/0438-1157.20200103
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Zero-dimensional (0D) materials derived from metal-organic frameworks (MOFs) are characterized by large specific surface area, high porosity and adjustable aperture. In recent years, they are widely used in lithium ion batteries, fuel cells, supercapacitors and other energy storage devices. Electrode material is a key factor in determining the electrochemical performance of supercapacitors. The application of zero-dimensional materials derived from MOFs in supercapacitors has broad prospects. In this paper, we reviewed the research progress of 0D materials derived from MOFs in supercapacitors. We summarized the current problems in this field, finally we look into the prospects of the future research trends.

Research progress in “bottom-up” chemical synthesis of nanographenes
Yating ZHANG, Bochao ZHANG, Jianlan ZHANG, Keke LI, Yongqiang DANG, Yingfeng DUAN
2020, 71(6):  2628-2642.  doi:10.11949/0438-1157.20200043
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Nanographene is a part of graphene structure, and its size is generally in the range of 1—100 nm. It can be used as a structural unit to construct functional carbon materials such as graphene, carbon nanotubes and fullerene. Due to the quantum-size effect, edge effect and interface effect, nanographenes are of potential for molecular electronics and the sensors. Herein, we will discuss the bottom-up chemical synthesis for nanographenes, including graphene molecules with seven- or eight-membered rings, heteroatom-doped nanographenes and edge functionalization of nanographenes. The advantages of different synthetic methods and their limitations are highlighed. The properties and applications of nanographenes with different structures have been summarized. The trends and key issues to be tackled in future are also briefly outlined.

Progress in synthesis of high temperature resistant polyimides with heterocyclic structure
Bin LI, Kaijun WANG, Shuang JIANG, Tianyong ZHANG, Ziran YAN, Di WANG, Yiwei LIU
2020, 71(6):  2643-2659.  doi:10.11949/0438-1157.20191571
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Polyimide (PI), as a widely used high-performance polymer material has unique structural characteristics and excellent comprehensive properties. The functionalized PI films can be used in many fields, such as gas separation films, flexible optoelectronic device substrates, etc. With the rapid development of science and technology, there are higher requirements for the performance of PI films. Thermal performance plays a very important role in many processes. PI with heterocyclic structure has strong rigidity, which makes it have excellent high temperature resistance, but at the same time there are problems such as difficulty in dissolving. In this paper, the research progress in recent years of PI with heterocyclic structure in high temperature resistance is reviewed. The synthesis of new monomers and corresponding PI, which containing pyrimidine, pyridine, benzimidazole and other heterocyclic structures, is emphasized. The characterization of its thermal and mechanical properties is summarized. The advantages and the problems caused by the special heterocyclic structure are pointed out. In addition, the prospects of the application and the development of high temperature resistant PI with heterocyclic structure are discussed.

Design, synthesis and application of high-performance carbon-based energy storage materials
Xiaobo WANG,Qingshan ZHAO,Zhinian CHENG,Haoran ZHANG,Han HU,Luhai WANG,Mingbo WU
2020, 71(6):  2660-2677.  doi:10.11949/0438-1157.20200508
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The performance of electrochemical energy storage device mainly depends on the electrode materials. Carbon materials have been widely applied in various energy storage systems due to their multitudinous advantages such as wide availability, excellent chemical stability, easy to modulate, and environmental friendliness. However, traditional carbon materials still suffer from problems such as low capacity density and poor rate performance. This review focuses on the design strategies for high-performance carbon-based energy storage materials, including pore structure regulation, heteroatomic doping, and combination with metal oxides. Their applications in lithium/sodium ion secondary batteries and supercapacitors are introduced. The advantages and disadvantages of these strategies are summarized, and the future research direction is also prospected. It has positive significance for the design and development of high-performance carbon-based energy storage electrode materials.

Material science and engineering, nanotechnology
Effects of composition distribution of catalytic slurry oils on optical texture of mesophase pitch
Xiaoyu DAI, Yuan en MA, Zhiming XU, Linzhou ZHANG, Suoqi ZHAO, Chunming XU
2020, 71(6):  2678-2687.  doi:10.11949/0438-1157.20200237
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Using SLO-LH, SLO-SH and SLO-YN catalytic cracking oil slurry as raw materials, mesophase pitch was prepared by thermal polycondensation method. The hydrocarbon composition distribution, boiling point distribution and nuclear magnetic structure characteristics of the oil slurry were systematically analyzed and related to mesophase pitch. The results show that the molecular weight and composition distribution of SLO-SH and SLO-YN are relatively narrow. The mesophase pitch was prepared under the given reaction conditions at 430 ℃ and 0.7 MPa. The obtained mesophase texture is mainly composed of domain and flow domain, and with less mosaic structure. The SLO-SH and SLO-YN optical texture index (OTI) are 45 and 50, respectively. Compared with SLO-SH and SLO-YN, the hydrocarbon composition and boiling point distribution of SLO-LH samples are significantly evacuated. The mesophase obtained from SLO-LH is mainly composed of a mosaic structure and a small domain. The results show that concentrated distribution and high aromatics content are conducive to high-quality mesophase pitch with high yield and high OTI value. Separation of oil slurry components is a necessary way to prepare high-quality mesophase pitch and needle coke.

Plating of Li ions in 3D structured lithium metal anodes
Rui ZHANG, Xin SHEN, Jinfu WANG, Qiang ZHANG
2020, 71(6):  2688-2695.  doi:10.11949/0438-1157.20200120
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Lithium metal has a very high theoretical specific capacity and a very low redox electrode potential, making it the most ideal anode material for a new generation of high specific energy secondary batteries. However, the large-scale practical applications of lithium metal batteries have been hindered by several issues on lithium metal anodes, such as uncontrollable lithium electroplating morphology and unstable solid electrolyte interphase (SEI) layer. Researchers have proposed plenty of strategies including three-dimensional (3D) structured lithium metal anodes to settle these challenges. The rational design of 3D structured lithium metal anodes requires a deep understanding of the mechanisms behind lithium metal batteries, which are extremely deficient at current initial stage. In this work, the mechanism of the areal surface area in 3D structured lithium metal anode on the electroplating process of lithium metal is quantitatively explored, and the two-stage mechanism of the areal surface area regulating lithium metal electroplating was revealed. At the early stage, higher areal surface area can provide more activated sites for electrochemical reactions, which can reduce the reaction resistance. While at the later stage, higher areal surface area may bring more narrow pores, which may hinder the lithium ion transport. In order to maximize the positive effect of 3D structured lithium metal anode in the early stage, the areal surface area and pore structure should be rational designed.

Optimization design of carbon molecular sieves and its I3- reduction performance
Chun YAO, Longlong HUANG, Jiangwei CHANG, Yiwang DING, Chang YU, Jieshan QIU
2020, 71(6):  2696-2704.  doi:10.11949/0438-1157.20191533
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The study compared the I3- reduction properties of four carbon materials, commercial carbon molecular sieve (CMS), multi-walled carbon nanotubes, activated carbon and reduced graphene oxide. The morphology and structure of the materials were characterized by FESEM, TEM and XRD, and their catalytic performance for $I3-$ reduction was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization test. Compared with other materials, CMS possesses the highest power conversion efficiency of 7.46% as the CE materials in DSSCs. The effects of annealing temperatures on themorphology, structure and electrocatalytic activity of CMS were also investigated. The as-made CMS800 via thermal annealing at 800oC achieves a high power conversion efficiency of 8.56%, which is significantly better than the precious metal Pt counter electrode, and at the same time shows better electrochemical stability than that of Pt.

Preparation of TiO2/PVDF blend microfiltration membrane and its adsorption of bilirubin
Jia JU, Wenxu QI, Pengfei KONG, Jiayu TANG, Feixue LIANG, Xiaoxin ZHANG, Gaohong HE, Lei YANG
2020, 71(6):  2705-2712.  doi:10.11949/0438-1157.20200081
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Bilirubin is an endogenous toxin, and accumulated in the body when hepatic injure is happened and excretion is hindered. The high level of bilirubin in the body, i.e., hyperbilirubinemia, manifests neurotoxicity, and threatens life even in serious case. Inorganic nanomaterials have attracted more and more attention as bilirubin adsorbents. However, some problems in bilirubin adsorption with using nanomaterials exist such as a decreasing adsorption efficiency due to agglomeration, and easy leakage because of small particle size. In this paper, TiO2/PVDF blend microfiltration membrane was prepared by dry-wet phase inversion, which the polyvinylidene fluoride (PVDF) as a matrix material, blended with nano-TiO2 particles, DMAc as solvent and PVP as porogen. When PVDF concentration was 10%(mass), TiO2 content was 1%(mass) and PVP content was 6%(mass), the prepared TiO2/PVDF blend microfiltration membrane showed significantly specific adsorption for bilirubin. SEM and EDX showed that TiO2 particles were evenly distributed in the membrane and in the pores without agglomeration. The effects of initial bilirubin concentration, adsorption time, adsorption temperature, pH and other adsorption conditions were also investigated.

Preparation of high-performance sodium acetate trihydrate-urea-expanded graphite mixed phase change material and its application performance in electric floor heating
Rui HUANG, Xiaoming FANG, Ziye LING, Zhengguo ZHANG
2020, 71(6):  2713-2723.  doi:10.11949/0438-1157.20200229
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Herein a high-performance sodium acetate trihydrate-urea-expanded graphite mixed phase change material (PCM) with a suitable melting point for use in electric floor heating was developed by employing urea to adjust the melting point of sodium acetate trihydrate, followed by adding expanded graphite to reduce the supercooling degree of the obtained binary mixture. The mixed PCM was fabricated into phase change panels with different thicknesses, followed by placing them into an electric heating floor of a test room, respectively. The effect of the thickness of the PCM layer on the thermal performance of the test room was investigated, and the set heating temperature was optimized. The results show that when the urea mass fraction is 36.5% and the amount of expanded graphite is 4%(mass), the melting enthalpy of the obtained mixed phase change material is as high as 209.1 J/g, the melting point is 31.98℃, and the supercooling degree is only 2.04℃ , thermal conductivity is 2.349 W/(m·K), good thermal reliability. It is found that, the thermal comfort of the test room increases with the increase in the thickness of the PCM layer, but the increase of the thickness also leads to the increase of heating time and electricity consumption; the heating time and electricity consumption decrease with the increase in the set heating temperature, while the thermal comfort of the test room tends to increase first and then decrease; when the thickness of the phase change material layer is 10 mm, the electric heating temperature is suitably set at 45°C. Compared to the reference room with a comparable thermal comfort, the test room equipped with the sodium acetate trihydrate-urea-expanded graphite mixed phase change panel with 10 mm in thickness presents the advantages of less electricity consumption and lower electricity cost, according to the time-of-use electricity price in Shanghai. It is revealed that the sodium acetate-urea-expanded graphite mixed PCM shows good potential for use in electric floor heating.

Few-layer graphene via electrochemically cathodic exfoliation for micro-supercapacitors
Feng ZHOU, Lijun TIAN, Lei GAO, Zhongshuai WU
2020, 71(6):  2724-2734.  doi:10.11949/0438-1157.20200259
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The use of graphite as a raw material for efficient, green, and low-cost preparation of few-layer graphene is of great significance for the large-scale production and application of graphene. However, the efficient exfoliation of graphite to graphene without use of strong oxidants and acids is still a great challenge. Herein, we developed a green and scalable aqueous-based electrochemical cathodic exfoliation approach, in which graphite as negative electrode can be electrochemically charged and expanded in an electrolyte of 6 mol·L-1 potassium hydroxide (KOH) under high current density and exfoliated efficiently into few-layer graphene sheets with the aid of sonication. The obtained few-layer graphene has low oxygen content [1.27% (mass)], few defects (ID/IG <0.035), a plate size of 5—10 μm, high conductivity of >200 S·cm-1, and good solution additivity. Moreover, such electrochemically exfoliated graphene (EG) nanosheets are readily used to produce highly solution-processable ink (1 mg·ml-1) in ethanol without the need of any surfactants, allowing for the production of large-area EG microelectrodes for EG based micro-supercapacitors (EG-MSCs). Furthermore, the as-fabricated aqueous EG-MSCs show ultrahigh scan rate of 100000 mV·s-1 and short time constant of only 24 ms. More importantly, using ionic liquids-based electrolyte of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide with bis(trifluoromethanesulfonyl)imide lithium salt (EMIMTFSI/LiTFSI), EG-MSCs can work at a high voltage of 4.0 V, and show high volumetric energy density of 113 mW·h·cm-3, outperforming the most reported MSCs (<50 mW·h·cm-3).

Surface modification and electrochemical properties of hard carbon anode material for lithium ion capacitors
He WANG, Nan QIN, Xin GUO, Junsheng ZHENG, Jigang ZHAO
2020, 71(6):  2735-2742.  doi:10.11949/0438-1157.20200071
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Concentrated sulfuric acid and concentrated nitric acid were used as oxidants to oxidize the surface of hard carbon by ultrasonic oxidation, and its electrochemical performance as a negative electrode material for lithium ion supercapacitors was studied. The influence of ultrasonic oxidation treatment on the morphology, structure and relative content of oxygen-containing functional groups on the surface were characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical performance of hard carbon before and after treatment was studied by means of galvanostatic charge and discharge, cyclic voltammetry and AC impedance. The results showed that ultrasonic oxidation treatment can introduce appropriate amount of oxygen-containing functional groups on the hard carbon surface, add additional active sites, improve the electron mobility, and then improve the electrochemical performance of hard carbon materials. In the half-cell test, at a high current density of 2 A·g-1, the specific capacity of oxidized hard carbon is twice that of untreated hard carbon, and it has excellent rate performance. Lithium ion capacitors were fabricated with oxidized hard carbon anode and activated carbon cathode. The energy density is 37.6 W·h·kg-1, and the power density is 9415 W·kg-1, the capacity retention rate was 99.1% after 4000 cycles at a current density of 1.0 A·g-1, showing good cyclic stability.

Preparation of nearly-stoichiometric TiN powder by chemical vapor deposition in fluidized-bed
Yuan SANG, Maoqiao XIANG, Miao SONG, Qingshan ZHU
2020, 71(6):  2743-2751.  doi:10.11949/0438-1157.20200077
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The traditional gas-solid reaction process for preparing TiN powder has an insurmountable internal diffusion control process, which has caused great difficulties in preparing high-purity, positive stoichiometric ratio TiN powder. Herein, to address the issue, a fluidized bed chemical vapor deposition (FBCVD) process was developed to fabricate high quality TiN powders based on TiCl4-N2-H2 system. The results showed that when the average particle size of TiN seeds was larger than 52.95 μm, they can realize long-term stable fluidization at 1000℃ even for 2 h and the obtained powders was nearly stoichiometric ratio TiN0.96. In addition, the oxygen content of obtained TiN powders decreased about 40% compared with raw TiN seeds. Moreover, the growth of TiN was controlled by the Volmer-Weber growth mode, which provides a new horizon for preparing high quality TiN powder in industry.

Highly dispersed SiO2/petroleum pitch-derived porous carbon composite as anode material for lithium-ion batteries
Zhengzheng XIA, Jialiang LIU, Jianjie NIU, Han HU, Qingshan ZHAO, Mingbo WU
2020, 71(6):  2752-2759.  doi:10.11949/0438-1157.20191370
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Silicon dioxide (SiO2) as anode material for lithium ion batteries has the characteristics of high theoretical capacity, low discharge potential, and low cost. However, its poor conductivity, severe volume expansion during charge and discharge processes, and rapid capacity decay hinders the practical application. By employing petroleum asphalt as the carbon source, silane coupling agent (KH-540) surface modified α-Fe2O3 as the template, highly dispersed SiO2/petroleum-based porous carbon composite (SiO2/PC) was prepared through carbonization, acid pickling procedures. Serving as anode material for lithium ion batteries, the prepared SiO2/PC exhibited excellent specific capacity and cyclability. The battery delivers a reversible specific capacity of 640 mA·h·g-1 after 900 cycles at a high current density of 1 A·g-1. The results show that the highly dispersed SiO2 was in-situ formed during the carbonization process, which could be tightly and firmly immobilized on the porous carbon surface. Such structure can efficiently prevent the agglomeration/pulverizationof SiO2 and buffer the volume expansion during charge and discharge processes, leading to the excellent electrochemical performance.

ZIF-derived porous carbon nanofibers for high-efficiency capacitive deionization
Lijun GAO, Silin BAI, Sucen LIANG, Ye MU, Qiang DONG, Chao HU
2020, 71(6):  2760-2767.  doi:10.11949/0438-1157.20200088
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As an environmentally-friendly and energy-saving desalination technology, capacitive deionization (CDI) is becoming an important desalination technology to replace reverse osmosis desalination and electrodialysis desalination. Carbon-based materials have been applied as promising CDI electrodes. However, most of them are powdered and binders are inevitably employed in the process of electrode fabrication, which causes a decline in electrosorption ability. Herein, monolithic porous carbon nanofibers with a flexible structure were synthesized by electrospinning and carbonizing the mixture of zeolitic imidazolate frameworks (ZIFs) and polyacrylonitrile (PAN). Due to the hierarchical porous structure and hydrophilicity, the as-synthesized porous carbon nanofibers exhibited a great salt adsorption capacity of 19.92 mg/g in 500 mg/L NaCl solution under the voltage of 1.2 V, which was two times higher than that of pristine carbon nanofibers.

Preparation of apigenin nanoparticles by combining subcritical water technology with freeze-drying processing
Jiyang TIAN, Yuanzuo ZOU, Yuan PU, Dan WANG
2020, 71(6):  2768-2779.  doi:10.11949/0438-1157.20200049
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Under the system of solvent(subcritical water)-antisolvent(deionized water), based on the combination of subcritical water technology and freeze-drying processing, we prepared apigenin nanoparticles by nanocrystallization and modification. The study comprehensively explores the influencing factors, including the temperature of desolvation, the temperature of subcritical water, the pressure of reaction system, and surfactant concentration in the process of the granulation. The study compares raw materials and products through scanning electronic microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR), X-ray diffraction (XRD) and mass spectrometry (MS). The results show that when the antisolvent temperature is 0℃, the subcritical water temperature is 160℃, the reaction pressure is 5 MPa, and the surfactant γ-cyclodextrin mass fraction is 5%, the particle size can be obtained at range 20—30 nm, the nanoparticles are evenly distributed, with high stability and low crystallinity. The preparation method of apigenin nanoparticles reported in this article, without the participation of organic solvents in the whole process, is easy for biomedical promotion, and provides a reference for the design and development of oral drugs based on apigenin.

Preparation of MOFs-derived hollow Co3O4/CdIn2S4 heterojunction with enhanced photocatalytic carbon dioxide reduction activity
Jinman YANG, Xingwang ZHU, Guli ZHOU, Hui XU, Huaming LI
2020, 71(6):  2780-2787.  doi:10.11949/0438-1157.20191416
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Photocatalytic carbon dioxide conversion technology can not only use inexhaustible solar energy, but also convert carbon dioxide into high-value-added carbon-based fuels, which has attracted extensive attention from researchers. Herein, we designed and fabricated the Co3O4/CdIn2S4 heterojunction photocatalyst with hollow structure to convert CO2. With series of measurement, the results show that the efficient coupling of the two materials could greatly promote photo-generated carriers separation and press the recombination of that, meanwhile, the introduction of MOFs template could help catalyst to expose more active sites. Based on the above unique advantages and compared to the pure CdIn2S4, the 5% Co3O4/CdIn2S4 heterojunction performs well in whole photocatalytic reduction process, which can generate the CO. And CO generation rate could be up to 74 μmol·g-1·h-1 and selectivity could be 100%.

Coal-based carbon quantum dots/carbon nitride composites for photocatalytic CO2 reduction
Ruizhe ZHANG, Keke LI, Kaibo ZHANG, Wei LIU, Lisi ZHENG, Yating ZHANG
2020, 71(6):  2788-2794.  doi:10.11949/0438-1157.20200096
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Using Taixi anthracite as a raw material, coal-based carbon quantum dots (C-CQDs) were prepared by chemical oxidation, and C-CQDs and urea were used as precursors to prepare coal-based carbon quantum dots/carbon nitride (C-CQDs /g-C3N4) composite materials. The composition and structure of the samples were characterized by means of TEM, XRD, FT-IR, UV-Vis and PL respectively, and the phoyocatalytic potential were assessed in terms of reduction CO2 into methanol under visible light irradiation. The results show that the C-CQDs were uniformly decorated on the surfaces of the C-CQDs/g-C3N4 composite, and the C-CQDs/g-C3N4 exhibited superior photoactivity, the methanol yield up to 28.69 μmol/(g cat), which is about 2.2 times in comparison with that of pure graphite carbon nitride (g-C3N4) in photocatalytic CO2 reduction.

Fabrication and stability of GO/Al2O3 composite nanofiltration membranes
Ju WANG, Shufeng NIU, Ying FEI, Hong QI
2020, 71(6):  2795-2803.  doi:10.11949/0438-1157.20200205
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Preparation and energy storage properties of flexible and self-supporting CNT/Si composite films
Lianghan LI, Xianlong JIAN, Sen ZHANG, Ming ZHANG, Yuping SUN, Xinchang WANG
2020, 71(6):  2804-2810.  doi:10.11949/0438-1157.20200146
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A method for preparing large-area CNT/Si flexible self-supporting film has been developed. The prepared CNT/Si composite film is adjustable in size and has good flexibility. As the anode of lithium-ion battery, the silicon load in the film has a significant effect on the specific capacity and cycle stability of the electrode. The CNT/Si composite electrode with 52% silicon load shows excellent electrochemical performance. The specific charge capacity of the electrode is 1156 mA·h/g at the current density of 1 A/g, 975 mA·h/g at the reversible charge capacity of 200 cycles, and the capacity retention rate is 84%.

Hydrophilic-hydrophobic CuBTC/PVDF composite membrane applied to membrane distillation anti-oil experiment
Yize WANG, Dewu WANG, Deyin HOU, Guangyu AN, Min TANG, Jun WANG
2020, 71(6):  2811-2820.  doi:10.11949/0438-1157.20191439
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To solve the problem of water scarcity, membrane distillation(MD) technology has been paid more and more attention to the application of seawater desalination and wastewater treatment, and membrane is an important part of membrane distillation. In the membrane distillation process, the membrane is easily contaminated by oily substances, so it is important to modify the membrane to achieve oil resistance. In this paper, the hydrophilic CuBTC organometallic framework (MOF) particles were synthesized by hydrothermal method. Then, using polyvinyl alcohol (PVA) as binder, CuBTC particles were attached to the membrane by suction filtration. Finally, PVA was crosslinked with glutaraldehyde (GA) to prepare a CuBTC/PVDF composite membrane having a hydrophilic-hydrophobic layer. X-ray diffraction analysis, scanning electron microscopy and specific surface area tests show that CuBTC has high purity, specific morphology and excellent properties. To solve the problem of water solubility of PVA, PVA is crosslinked with glutaraldehyde to cure PVA, and the obtained product has excellent stability. The contact angle, pore size, pore size distribution and porosity of the composite membrane with four different CuBTC contents were analyzed. The results show that CuBTC particles have a large specific surface area and pore volume. CuBTC particles can be firmly suction filtered on the surface of PVDF membrane, which has high thermal stability and good flexibility. The oil-containing high-salt solution prepared with 1 g/L crude oil and 35 g/L sodium chloride was used as the feed liquid to conduct DCMD anti-oil pollution test on the original membrane and the composite membrane. It was found that the original membrane was quickly blocked by oil pollution, and the composite membrane had good resistance, which can be applied to long-term membrane distillation experiments.

Preparation and modification of ZIF-67 derived Co/NC porous carbon composite for electrocatalytic oxygen evolution reaction
Lei ZOU, Guoqiang LIU, Miaomiao JIANG, Zeheng YANG, Weixin ZHANG
2020, 71(6):  2821-2829.  doi:10.11949/0438-1157.20191040
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A porous carbon composite (R-Co / NC-800) with oxygen vacancies on its surface was prepared by pyrolyzing the precursor ZIF-67 at high temperature and using NaBH4 reduction. The structure, morphology, element distribution and valence state of the as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscope (XPS), respectively. The electrocatalytic performance of the as-prepared catalysts for oxygen evolution reaction (OER) was investigated by linear polarization curve (LSV) measurements. The R-Co/NC-800 with rich oxygen vacancies as electrocatalytic active sites and high specific surface area to expose amounts of unsaturated coordinate metal species after reconstruction the surface of Co/NC-800 via NaBH4 solution, which exhibits higher catalytic activity for OER, delivering a current density of 10 mA/cm2 at a low overpotential (287 mV) than that of Co/NC-800 (363 mV) in 1.0 mol/L KOH media, as well as outstanding long-term electrochemical durability.

Electrochemical properties of supercapacitor electrode materials made from needle coke
Xiaoqian XU, Junxia CHENG, Yaming ZHU, Lijuan GAO, Shiquan LAI, Xuefei ZHAO
2020, 71(6):  2830-2839.  doi:10.11949/0438-1157.20191296
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Activated carbons for supercapacitor electrode material were prepared by using coal-based needle coke as raw material and KOH as activator. The electrochemical properties of activated carbons were tested in a three-electrode electrochemical system with 3 mol/L KOH as electrolyte. The effect of the amount of activator on the electrochemical properties of the carbon electrode material was investigated. The results show that the electrochemical properties of the activated carbon increases gradually with the increase of the KOH/coke mass ratio during the activation process. When the carbon and alkali ratio is 1∶3, the specific surface area of the activated carbon reaches 2572.7 m2/g. The specific capacitance of the activated carbon is 316 F/g at a current density of 1 A/g. The capacitance retention rate is 95.7% after 5000 cycles with the coulombic efficiency remaining at 97.0%. The electrochemical performance of the activated carbon was further investigated in a two-electrode system. In the electrolyte of 1 mol/L Na2SO4, and at a widened voltage window of 1.8 V, the cyclic voltammetry curve is also in good rectangular shape, leading to an energy density of 20.8 W·h/kg and a power density of 230 W/kg.

Self-sacrificing templated preparation of nitrogen-doped molybdenum carbide/carbon as hydrogen evolution electrocatalyst
Xiaoming FAN, Xikui CHEN, Zihan WANG, Shuai CAO, Fengru CHENG, Zeheng YANG, Weixin ZHANG
2020, 71(6):  2840-2849.  doi:10.11949/0438-1157.20200207
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Using g-C3N4 as self-sacrificing template and nitrogen source, glucose as carbon source, and ammonium molybdate as molybdenum source, nitrogen-doped molybdenum carbide modified carbon nanosheets (N-Mo2C/C) with two-dimensional nanostructures were prepared and evaluated its electrocatalytic hydrogen evolution performance. X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), Raman spectroscopy, etc. were employed to analyze the compositions, morphologies and microstructures of the as-prepared N-Mo2C/C. The results show that ultrafine nitrogen-doped Mo2C nanoparticles with a diameter of 3—5 nm can be uniformly distributed on the 2D carbon nanosheets. The electrocatalytic performances of N-Mo2C/C for hydrogen evolution were tested by using an electrochemical workstation, which demonstrates that the N-Mo2C/C only exhibits an overpotential of 185 mV at 10 mA/cm2 in 1 mol/L KOH solution, and a stable hydrogen evolution potential could be maintained for 20 h in a long-term cycling test.

Regulation of support structure by TiO2 deposition and its effect on performance of GO membranes
Jingran NIU, Huining DENG, Wei ZHANG, Baisong HU, Shaofeng ZHANG
2020, 71(6):  2850-2856.  doi:10.11949/0438-1157.20200108
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A polyethersulfone (PES) ultrafiltration membrane modified with polydopamine (PDA) was deposited by different amounts of titanium dioxide (TiO2) nanoparticles to fabricate support membranes with different morphology for graphene oxide (GO) composite membranes. The prepared GO membranes with and without TiO2 were characterized by SEM, water contact angle analyses, Zeta potential and XRD. The results indicated that the TiO2 clusters distributed on the surface of the PES membrane uniformly and showed an increased density with the increase of the deposited TiO2 amount. The peak and valley structures on the surface of membranes could be seen even after GO deposition. The interlayer spacing of GO did not change obviously with the deposition of TiO2 layer. The TiO2/GO membranes showed enhanced water flux with the amount of deposited TiO2. This increase in flux is more obvious when the GO deposition is low. When the amount of GO deposition was 4.11 μg/cm2 and TiO2 was 20.55 μg/cm2, the water flux of the composite membrane was 108.38% higher than that without TiO2. The rejection performance of the composite membrane for inorganic salt solutions is mainly based on the negatively charged Donan repulsion effect on the membrane surface. The rejection of Congo red of the prepared TiO2/GO membranes was higher than 99%. The rejection of methyl orange was up to 82%. The addition of the TiO2 intermediate layer did not reduce the rejection effect of the composite membrane.

Preparation of M-MOF-74 (M = Ni, Co, Zn) and its performance in electrocatalytic synthesis of ammonia
Tong YANG, Xiaobo HE, Fengxiang YIN
2020, 71(6):  2857-2870.  doi:10.11949/0438-1157.20200015
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The conversion of nitrogen rich in nature into ammonia is vital to the development of human society. The electrochemical synthesis of ammonia using nitrogen and water as raw materials has been regarded as a promising and environmentally friendly process. In this work, Ni-, Co- and Zn-MOF-74 were prepared by hydrothermal synthesis, and were characterized by XRD, SEM and XPS. Their catalytic performance was investigated in 0.1 mol·L-1 Na2SO4 electrolyte. The results show that Ni-MOF-74 has better electrocatalytic performance for ammonia synthesis than Zn- and Co-MOF-74 catalysts. Ni-MOF-74 can achieve the high NH3 yield (6.68 × 10-11mol·s-1·cm-2) and high Faraday efficiency (23.69%) at -0.7 V (vs Ag/AgCl). Ni-MOF-74 has not only the small particle size with uniform distribution, but also the greatest number of metal-oxygen bonds and the largest electrochemical specific surface. Specially, Ni-MOF-74 can effectively inhibit hydrogen evolution side effect, which results in enhanced the Faraday efficiency.

Properties of self-healing epoxy resin containing PEGDE segments based on Diels-Alder dynamic covalent bond
Lunliang ZHANG, Liying WAN, Juntong HUANG, Xibao LI, Zhijun FENG, Zhi CHEN
2020, 71(6):  2871-2879.  doi:10.11949/0438-1157.20191567
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The dienyl structure-containing furan methylamine was used to link the hard segment E-51 epoxy resin (EP) modified by bisphenol A and the soft segment PEGDE to form linear macromolecules, and reacted with bismaleimide containing dienophilic structure to synthesize the soft-hard-soft structure of the intrinsic self-healing epoxy (EP-DA) via thermo reversible Diels-Alder (DA) reaction. The structure and performance of EP-DA were characterized by FTIR, DSC, TGA and electronic universal testing machine. The results show that: DA dynamic covalent bond is successfully introduced into EP-DA, and the temperature of DA forward and reverse reaction is 60 ℃ and 122 ℃ respectively. When the PEGDE and EP content in the EP-DA segment each accounts for 50%, its heat resistance and tensile strength reach the best, the epoxy resin exhibits good reprocessing properties and multiple self-repairing properties. After the damaged specimen is repaired at 60℃ for 4 h, the crack is healed, and the first repair rate is 88. 41%. After three repairs of the same specimen, the repair rate is still more than 68%.

Preparation of coral-like nitrogen-doped porous carbons and its supercapacitive properties
Honghui BI, Shuai JIAO, Feng WEI, Xiaojun HE
2020, 71(6):  2880-2888.  doi:10.11949/0438-1157.20191428
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Under the condition of melamine as the nitrogen source and potassium carbonate as the activator, coral-like nitrogen-doped graded porous carbons (CNPCs) were prepared from rapeseed cake. Field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and desorption techniques were used to study the effects of melamine dosage on the morphology, composition and pore structure of CNPCs. The results show that the as-prepared CNPC2 has a high surface area up to 2050 m2·g-1 when the dosage of melamine is 2 g. The specific capacitance of CNPCs is up to 274 F·g-1 at a current density of 0.05 A·g-1 in 6 mol·L-1 KOH electrolyte. As the current density increases to 50 A·g-1, the specific capacitance of CNPCs retains 169 F·g-1, showing excellent rate performance. After 10000 charge and discharge cycles, the capacitance retention is 96%, demonstrating good cycle stability. This work provides a simple, green method for the mass production of high-performance porous carbon materials for energy storage from biomass.

Synthesis and characterization of copper-based graphene composite catalyst
Yongsheng WANG, Xiaolin LAN, Tian QIU, Xinping ZHANG, Yingying WU, Li CHEN, Weixiang XU, Dongjie GUO, Zhengkang DUAN
2020, 71(6):  2889-2899.  doi:10.11949/0438-1157.20200075
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A Cu/rGO catalyst was prepared by in-situ hydrothermal method and terephthalic acid (TPA) was introduced to modify the copper-based graphene composite material. The effects of different solvents, hydrothermal time and precipitation pH on microstructure characteristics of Cu/rGO catalyst material introduced by TPA were investigated. The effect of different molar ratios of copper and melamine on the catalyst was studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 physical adsorption and desorption test (BET) were used to investigate the morphology and structure of the catalyst. The catalytic performance of the catalyst for the dehydrogenation of diethanolamine was investigated. The results showed that with ethanol and water volume ratio of 1∶1 for the bases for solvent, the pH of the solution was 13.0, and reaction under 160℃ for 10 h, the preparation of the catalyst performance was the best, IDA yield was 86.55%. Compared with Cu/rGO catalyst without TPA, the yield of iminodiacetic acid increased by 20%. The addition of TPA and GO showed the best reduction effect, the interaction between TPA and GO were the strongest and stable Cu2O, make its crystallinity better, and increase the catalyst active site, to improve the reaction rate. GO has a folded lamellar structure. After reduction, the Cu nanoparticles with a particle size of about 10 nm are evenly distributed on the rGO surface of the corrugated sheet structure to improve the anti-sintering performance of the catalyst.

Preparation and properties of graphene oxide hybrid molecularly imprinted composite membranes
Dongyang MAO, Dan YANG, Jieping FAN
2020, 71(6):  2900-2911.  doi:10.11949/0438-1157.20200002
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Graphene oxide (GO) was prepared by the improved Hummers method and freeze-drying method. With synephrine hydrochloride as the template molecule, water-soluble acrylamide as the functional monomer, and ionic liquid (1-butyl-3-methylimidazole bromide) as the porogen, GO was added to the polymerization solution to prepare graphene oxide hybrid molecularly imprinted composite membrane (GO-MIM). Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and infrared spectroscopy were used to characterize GO and GO-MIM. By combining molecularly imprinted membrane technology with GO, the mechanical properties of MIM are significantly improved. Adsorption and permeation experiments show that GO-MIM can be used in pure water solvent system and has a good selective adsorption capacity and preferential permeability for synephrine hydrochloride.

Control of magnetic field to luminescence characteristics in (C4H9NH3)2(CH3NH3)Pb2I7 perovskite
Yaqian WANG, Xiao LU, Bo PENG
2020, 71(6):  2912-2917.  doi:10.11949/0438-1157.20200078
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(C4H9NH3)2(CH3NH3)Pb2I7 is a Ruddlesden-Popper phase perovskite material, has a layered structure, and the layers are combined by van der Waals forces. The two-dimensional layered perovskite can be obtained by mechanically exfoliated from bulk crystals, which display strong bound exciton spontaneous emission. The helicity parameter of the bound exciton is linear to the external magnetic field, giving rise to a giant Lande factor difference (Δg) of about 0.43 between the electron and hole of bound exciton. The antimagnetic effect leads to a redshift of bound exciton emission in magnetic field.