GREEN CHEMISTRY
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2019
·Vol. 22
·期 3
·742-752
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IF 9.405
Xiwei Hu,Xun Sun,Qiang Song,Yangyang Zhu,Yu Long,Zhengping Dong
Metal-free carbon catalysts with excellent catalytic performance have drawn much research attention recently. Herein, polymer-derived N,S co-doped carbon catalysts (PDNSC-X) with a hierarchically porous structure were facilely prepared by a cost-effective and convenient strategy via carbonization of a N- and S atom-containing polymer precursor and were subsequently used as efficient metal-free catalysts. The catalytic activity of the as-fabricated PDNSC-800 was greater than those of other reported heteroatom-doped carbon catalysts in catalytic reduction of various nitroarenes. The high catalytic activity of PDNSC-800 was related to the synergistic effects of a high surface area, a hierarchically porous structure, abundant N- and S-containing active sites, and defect formation. In addition, the close relationship between the N species (especially pyrrolic N) and high selectivity in metal-free catalytic synthesis was investigated in the reduction of nitroarenes and selective oxidation of ethylbenzene. This study may provide a new strategy to fabricate specific heteroatom-doped metal-free carbon catalysts for environmentally friendly efficient organic transformation.
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ACS Catalysis
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2019
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IF 12.221
Muhong Li,Feifei Bi,Yida Xu,Panpan Hao,Kun Xiang,Yu Zhang,Shanyong Chen,Jia Guo,Xuefeng Guo,Weiping Ding
An oxide catalyst plays an important role in environmental catalysis. Metal chlorides are widely used as precursors in the preparation of oxide catalysts. However, residual chlorine usually influences the performance of catalysts. In this work, we systematically investigate the influence and efficient removal of chlorine residue on the Co3O4 catalyst in CO oxidation by control experiments and related characterizations. Compared to the cobalt nitrate-derived catalyst, the cobalt chloride-derived Co3O4 catalyst shows a significant improvement in catalytic activity after being washed with water, suggesting that residual chlorine exerts a detrimental effect on the Co3O4 catalyst in CO oxidation. Further investigations show that residual chlorine inhibits the activity of surface oxygen species as well as blocks the active sites. It is noteworthy that residual chlorine cannot be efficiently removed before the calcination because of the strong interactions between the chloride anions and cobalt precursor. In addition, the washed chloride-derived catalyst even shows a better catalytic performance than the nitrate-derived one because of more active sites that are exposed on the surface with the removal of residual chlorine. More importantly, most of the commercial Co3O4 samples are found to be seriously poisoned by chlorine. Hence, efficient elimination of residual chlorine is very important and should be undertaken before the use of catalysts in the case of using chlorides as precursors.
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SENSORS AND ACTUATORS B-CHEMICAL
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2019
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IF 6.393
Ya Xiong,Xiao Chang,Xurong Qiao,Kun Li,Lei Zhu,Fujun Xia,Xiaofang Li,Qingbin Zheng,Wei Xing,Qingzhong Xue
For the first time, Co-MOF-74 derived Co 3 O 4 /graphene heterojunction nanoscrolls (Co 3 O 4 /GNS) structure is synthesized by a simple one-step hydrothermal strategy and subsequent calcination process. Theoretically, the growth mechanism of Co 3 O 4 /GNS is revealed by molecular dynamic simulation, demonstrating that a high loading of Co-MOF-74 nanoparticles is needed for effective rolling of GO. The sensor based on Co 3 O 4 /GNS exhibits high response of 58.1 (34-fold enhancement compared with that of Co 3 O 4 ), short response/recovery time of 12 s/66 s (157 s/200 s for Co 3 O 4 ) toward 1 ppm acetone at 190 °C and superior selectivity, which are much better than those of most reported acetone sensors. Moreover, the Co 3 O 4 /GNS can even detect as low as 50 ppb acetone with a notable response (1.24). The appreciable response together with rapid response/recovery of Co 3 O 4 /GNS is attributed to the large heterojunction interface between Co 3 O 4 and graphene nanoscroll and high-speed gas transfer pathways provided by nanoscroll. This unique structure design is believed to offer guidance for generalizable synthesis of metal oxide/GNS that can be effectively applied in the fields of ppb-level gas detection.
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JOURNAL OF CATALYSIS
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2019
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IF 7.723
Xiaoyong Xu,Lou Pan,Qiutong Han,Chengzhong Wang,Peng Ding,Jing Pan,Jingguo Hu,Haibo Zeng,Yong Zhou
Molybdenum sulfide (MoS 2 ) has attracted considerable attention as one of noble-metal-free co-catalysts of hydrogen evolution reaction (HER) for artificial photosynthetic water splitting. There are well-known challenges in optimizing its catalytic activity to pursue the replacement of platinum (Pt) for HER, owing to the edge-limited active sites and intrinsically poor conductivity. Herein, we prepared metallic MoS 2 nanodots (MNDs) with 1T-phase occupation and edge-exposure maximum to achieve the simultaneous optimization of electric conductivity and active sites. When integrated as co-catalysts with graphitic carbon nitride (g-CN) for sunlight-driven HER in alkaline electrolyte, the outstanding photocatalytic activity with hydrogen evolution rate of 5.62 mmol g −1 h −1 , over 280 times higher than that of pure g-CN, demonstrates the excellent co-catalytic performance of 1T-MoS 2 NDs (1T-MNDs) that even comparable to state-of-the-art Pt. The photo-induced charge dynamics describe the role of 1T-MNDs in facilitating charge separation as well as surface catalytic reaction, suggesting a promising potential of 1T-MNDs with more active sites and higher conductivity as Pt-alternative co-catalysts for solar hydrogen production.
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COLLOIDS AND SURFACES B-BIOINTERFACES
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2018
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IF 3.997
Shengnan Wang,Yuanyi Yang,Yunfei Li,Jiacheng Shi,Jianshu Zhou,Li Zhang,Yi Deng,Weizhong Yang
Polyetheretherketone (PEEK)-based implants have become popular in hard tissue orthopedic and dental field. However, its inherent bio-inertness limited its applications for bone repair/substitution of osteoporosis patients, with poor osteogenesis capability. In order to ameliorate their bioactivity, the 3D porous PEEK substrate was created by sulfonate processing, and the substrate was subsequently incorporated with strontium (Sr) through a hydrothermal reaction in Sr(OH) 2 solutions. The adiponectin (APN) protein membrane was deposited on the substrate via polydopamine-assisted deposition. Surface characterization results disclosed that the nanostructures had been formed on sPEEK-Sr-APN surafces, and APN coatings on the substrates could adjust Sr release rate and further mediate cell-material interactions. in vitro experiments indicated that the cellular effects (proliferation and differentiation) of MC3T3-E1 were significantly increased with Sr/APN coordinated regulation. This study provides bioactive Sr and APN as promising active components for bio-functional bone regeneration/substitution, and optimizes the osteointegration of PEEK implants in clinic.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2018
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IF 3.141
Hongzhou Xie,Linbo Wu,Bo-Geng Li,Philippe Dubois
Poly(ethylene-co-hexamethylene 2,5-furandicarboxylate) (PEHF) copolyesters with high intrinsic viscosity were synthesized from 2,5-furandicarboxylic acid (FDCA), ethylene glycol (EG), and 1.6-hexanediol (HDO) through two-step melting polycondensation, characterized with 1H NMR, DSC, WAXD, and TGA, and assessed by tensile and impact tests. The molar fraction of HF unit in PEHF (ϕHF), namely, copolymer composition, is higher than the molar fraction of HDO in the feeding diols and can be predicted empirically via Mayer–Lewis equation with apparent reactivity ratio rHDO = 4.6 and rEG = 0.74. All the PEHFs exhibited a single glass transition temperature and excellent thermal stability. HF-rich (ϕHF ≥ 88 mol %) PEHFs are semicrystalline but the others are almost amorphous. In comparison with PEF, PEHFs with ϕHF of 28–36 mol % possess significantly improved tensile ductility (elongation at break 54–160%) and retain high tensile modulus (2.6–2.2 GPa) and yielding strength (71–65 MPa). The tensile properties are comparable to those of bottle-grade PET.
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Journal of Materials Research and Technology-JMR&T
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2018
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IF 3.398
Ming Li,Xiaoli Xi,Zuoren Nie,Liwen Ma,Qingqing Liu
The recycling of WC–Co hard metal scraps has been taken into consideration in the literature, due to the release of toxic substances and long recovery process. In this study, the recovery of tungsten process, based on the molten salt electrolysis treatment of WC–Co hard metal scraps, was developed. The anode polarization curves were applied to investigate the dissolution of the WC–Co hard metal scrap. Then, the electrochemical behavior of tungsten and cobalt ions dissolved from WC–Co scrap anode, was studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). The results demonstrated that the reduction of tungsten and cobalt ions occurred through a one-step process involving the transfer of two electrons. This process was achieved by the diffusion of tungsten and cobalt ions in the melts. Finally, the parameters, such as the electrolysis current, the electrolysis duration and temperatures, were applied to analyze the effect of different electrolysis conditions on the composition of recycled products. The results demonstrated that the electrolysis current and the electrolysis temperature, compared to electrolysis duration, have significant effects on the selectivity of tungsten recycling. Furthermore, the analysis of cathode products demonstrated that a tungsten powder of approximately 500 nm could be selectively recovered from WC–Co hard metal scrap with the electrolysis condition of 60 mA for 4 h at 1073 K in NaF–KF molten salt.
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CERAMICS INTERNATIONAL
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2018
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IF 3.057
Yaxiong Du,Hongfei Chen,Guang Yang,Bin Liu,Yanfeng Gao,Hongjie Luo
Titanium carbide based cermets are promising wear resistant coating materials used at elevated temperatures in hostile environment owing to their excellent mechanical, physical and chemical properties. In this work, TiC-Co composite coatings with different Co content, as well as a WC-17Co reference coating are prepared by plasma spraying and their wear resistances are investigated. The friction coefficients and wear rates tested by dry sliding friction at 600 °C are used to characterize the high-temperature wear resistance of the coatings. The phase and microstructure evolution of the coatings before and after friction test are evaluated to conclude the wear mechanisms of these coatings. The results show that as-prepared TiC-Co composite coatings are composed of TiC, Ti, α-Co, r-TiO 2 and CoO phases and Ti oxidizes to r-TiO 2 phase during friction test, which is resulted from decarburization and oxidation of TiC. Among all the coatings, TiC-15Co has the minimum friction coefficient and lowest wear rate. It is contributed to the balanced ratio and good bonding between Co-rich soft phases and Ti-rich hard phases. The wear mechanisms of TiC-Co composite coatings are abrasive wear for low Co content (<15 wt%) coatings and adhesion/fatigue wear for high Co content ones.
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ACS Sustainable Chemistry & Engineering
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2018
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IF 6.14
Han Hu,Ruoyu Zhang,Jinggang Wang,Wu Bin Ying,Jin Zhu
A series of biobased poly(butylene carbonate-co-furandicarboxylate) (PBCF), are synthesized through a two-step polycondensation reaction. Chemical structures, thermal properties, crystallization behaviors, mechanical properties, barrier properties, and enzymatic degradation of PBCFs are investigated. The linear variation of the glass transition temperatures with the content ratio confirms the good miscibility between butylene carbonate (BC) and butylene furandicarboxylate (BF) units. BF segments could crystallize in most contents under different temperatures. Consequently, mechanical properties of these copolymers depend not only on the composition but also on the annealing conditions. Long-time annealing at room temperature or short-time annealing under high temperature could tremendously increase the tensile modulus. For room-temperature annealing, the formation of less perfect crystals of the poly(butylene furandicarboxylate) (PBF) could interpret the enhancement of modulus. On the other hand, the high-temperature annealing induces more perfect PBF crystals and improves the modulus significantly too. The tensile toughness of the PBCFs is good with the lowest elongation at break of 260%, and the degradation could be observed in samples with less than 60 mol % BF units. With good gas barrier properties, fast biodegradability, and high mechanical performance, these copolyesters possess potential applications in the plastic industry.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2018
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IF 5.091
Yahui Sun,Kaixi Li,Jianghong Zhao,Jianlong Wang,Nan Tang,Dongdong Zhang,Taotao Guan,Zuer Jin
Millimeter-sized nitrogen and sulfur co-doped microporous activated carbon spheres (NSCSs) were first synthesized from poly(styrene-vinylimidazole-divinylbenzene) resin spheres through concentrated H 2 SO 4 sulfonation, carbonization and KOH activation. Styrene (ST) and N-vinylimidazole (VIM) were carbon and nitrogen sources, while the sulfonic acid functional groups introduced by the simple concentrated sulfuric acid sulfonation worked simultaneously as cross-linking agent and sulfur source during the following thermal treatments. It was found that the surface chemistries, textural structures, and CO 2 adsorption performances of the NSCSs were significantly affected by the addition of VIM. The NSCS-4-700 sample with a molar ratio of ST: VIM = 1: 0.75 showed the best CO 2 uptake at different temperatures and pressures. An exhaustive adsorption evaluation indicated that CO 2 sorption at low pressures originated from the synergistic effect of surface chemistry and micropores below 8.04 Å, while at the moderate pressure of 8.0 bar, CO 2 uptake was dominated by the volume of micropores. The thermodynamics suggested the exothermic and orderly nature of the adsorption process , which was dominated by a physisorption mechanism. The high CO 2 adsorption capacity, fast kinetic adsorption rate, and great regeneration stability of the nitrogen and sulfur co-doped activated carbon spheres indicated that the as-prepared carbon adsorbents were good candidates for large-scale CO 2 capture.
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Nanomaterials
·
2018
·Vol. 8
·期 5
·275
·
IF 3.504
Jingting Lu,Chengli Jiao,Zeeshan Majeed,Heqing Jiang
Mesoporous carbons (MC) have attracted a tremendous amount of interest due to their efficient molecular transport properties. However, the limited number of active sites and low microporosity generally impede their use for practical applications. Herein, we have fabricated Mg and N co-doped mesoporous carbon (Mg-NMC) with high microporosity via one-pot synthetic route followed by further steam activation. In comparison with the parent N-doped mesoporous carbon, Mg-NMC shows partially ordered mesostructure and improved CO2adsorption capacity attributed to the introduction of basic site after Mg doping. Upon further steam activation, the microporosity is enhanced to 37.3%, while the CO2adsorption capacity is also increased by 70.4% at 273 K and 1.0 bar.Keywords:mesoporous carbon;Mg doping;steam activation;basic site;microporosity;CO2adsorption
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FUEL PROCESSING TECHNOLOGY
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2019
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IF 4.507
Ke Wang,Youwei Zhao,Peter T. Clough,Pengfei Zhao,Edward J. Anthony
Structurally modified and improved NaBr-co-doped Li 4 SiO 4 ceramics were developed for CO 2 absorption in low-CO 2 -concentration atmospheres. Pure and NaCl-doped Li 4 SiO 4 ceramics were also prepared for comparison. The samples were analyzed by X-ray diffraction, Scanning Electron Microscopy, N 2 adsorption, X-ray photoelectron spectroscopy, differential scanning calorimetry , and thermogravimetric analyses (dynamic and isothermal). The sorption kinetics were obtained using a double exponential model. The results showed that both Na and Br can be introduced into the Li 4 SiO 4 structure and doped on Li and oxygen sites, respectively. The doped sample presented a Li 2 O-enriched surface, guaranteeing abundant Li O sites and are significantly different from previous anionic (CO 3 , F and Cl) doping of Li 4 SiO 4 , Br doping also generated macroporous features with small particle size, these favorable characteristics promoted the surface chemisorption kinetics. Moreover, DSC analysis confirmed the formation of the molten phases during CO 2 absorption, which helps improve the lithium diffusion kinetics . Here, 0.1 mol NaBr doping was used to reach a maximum absorption capacity (>30.0 wt%) in 15 vol% CO 2, suggesting that NaBr-doped Li 4 SiO 4 ceramics have great potential for CO 2 capture at high temperature.
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