Nature Energy
·
2018
·Vol. 3
·期 12
·1067-1075
·
IF 46.859
Gao Wenbo,Guo Jianping,Wang Peikun,Wang Qianru,Chang Fei,Pei Qijun,Zhang Weijin,Liu Lin,Chen Ping
Ammonia is a promising carbon-free energy carrier, but is currently synthesized industrially under harsh conditions. Synthesizing ammonia using lower temperatures and pressures could therefore improve its prospects as a chemical means to store and transport energy. Here we report that alkali and alkaline earth metal imides function as nitrogen carriers that mediate ammonia production via a two-step chemical looping process operating under mild conditions. Nitrogen is first fixed through the reduction of N 2 by alkali or alkaline earth metal hydrides to form imides and, subsequently, the imides are hydrogenated to produce NH 3 and regenerate the metal hydrides. The oxidation state of hydrogen therefore switches between −1 (hydride), 0 (H 2 ) and +1 (imide and NH 3 ). Late 3d metals accelerate the reaction rates of both steps. The chemical loop mediated by BaNH and catalysed by Ni produces NH 3 at 100 °C and atmospheric pressure.
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CERAMICS INTERNATIONAL
·
2018
·
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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ANALYTICAL CHEMISTRY
·
2019
·
IF 6.35
Haifang Liu,Jie Yang,Zhaohui Li,Lehui Xiao,Aaron Albert Aryee,Yuanqiang Sun,Ran Yang,Hongmin Meng,Lingbo Qu,Yuehe Lin,Xiaobing Zhang
Carbon dots (CDs) are emerging as powerful tools for biosensing and bioimaging because of their intrinsic properties such as abundant precursors, facile synthesis, high biocompatibility, low cost, and particularly robust tunability and stability. In this work, a new type of CDs was prepared from m-phenylenediamine and folic acid by hydrothermal method. Interestingly, the as-prepared CDs show blue emission in non-hydrogen-bonding solution, whereas robust green emission in hydrogen-bonding solution. Based on this phenomenon, a novel fluorescence sensing mechanism named as hydrogen-bonding-induced emission (HBIE) was proposed. The HBIE-CDs have large Stokes shift (141 nm) in water, good biocompatibility, and ultrasmall size, which facilitates their translocation into living cells. Very importantly, the as-prepared HBIE-CDs show strong affinity toward nucleic acid without interference from other biological species. After binding with DNA/RNA through hydrogen bond, as high as 6-fold green fluorescence enhancement of HBIE-CDs was observed. Since the nucleus is rich in DNA/RNA, these HBIE-CDs were successfully used for rapid and, especially, wash-free subcellular in situ imaging of the nucleus in living cells in a fluorescence turn on mode, which has a great practicability to be used for nucleus imaging in bioanalytical studies and clinical applications.
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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2019
·
IF 4.084
Darvaish Khan,Jianxin Zou,Mingguang Pan,Zhewen Ma,Wen Zhu,Tianping Huang,Xiaoqin Zeng,Wenjiang Ding
In this study, MgH 2 and Co powders were mechanically milled in the molar ratio 2:1 and compressed to hard-packed cylindrical pellets. The microstructure, phase changes, and hydrogen storage properties of the mechanically milled 2MgH 2 Co powder and the 2MgH 2 Co compressed pellet were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and synchronous thermal (DSC/TG) analyses. Dehydrogenation of the 2MgH 2 Co compressed pellet is mainly due to the decomposition of Mg 2 CoH 5 while it is the dehydriding of MgH 2 for the milled 2MgH 2 Co powder. Pressure composition absorption isotherms of the 2MgH 2 Co powder and 2MgH 2 Co compressed pellet show two and three plateaus, respectively, corresponding to the formation of Mg 6 Co 2 H 11 and Mg 2 CoH 5 hydride phases . For the compressed 2MgH 2 Co pellet, enthalpies of formation/decomposition were measured to be −58.11±7.69 kJ/mol H 2 /55.70±3.34 kJ/mol H 2 for Mg 2 CoH 5 and -81.89±10.39 kJ/mol H 2 /74.47±5.27 kJ/mol H 2 for Mg 6 Co 2 H 11 . In contrast, hydrogenation/dehydrogenation enthalpies of Mg 2 CoH 5 and Mg 6 Co 2 H 11 mechanically milled 2MgH 2 Co powder were −73.98±10.1 kJ/mol H 2 /71.67±1.38 kJ/mol H 2 and -96.86±8.73 kJ/mol H 2 /89.95±10.81 kJ/mol H 2 , respectively. Fast hydrogenation was observed in the dehydrided 2MgH 2 Co compressed pellet with about 2.75 wt% absorbed in less than 1 min at 300 °C and a maximum hydrogen storage capacity of 4.43 wt% (2.32 wt% for the 2MgH 2 Co powder) was achieved. The hydrogen absorption activation energy of the 2MgH 2 Co compressed pellet (64.34 kJ-mol −1 H 2 ) is lower than the mechanically milled 2MgH 2 Co powder (73.74 kJ-mol −1 H 2 ). The results show that mechanical milling followed by high-pressure compression is an efficient method for the synthesis of Mg-based complex hydrides with superior hydrogen sorption properties .
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ANALYTICA CHIMICA ACTA
·
2018
·
IF 5.123
Yang Li,Qingfen Niu,Tao Wei,Tianduo Li
A novel bifunctional thiophene-based Schiff base TS as a colorimetric and fluorescent turn-on sensor for rapid and simultaneous detection of Al 3+ and Zn 2+ ions with high selectivity and sensitivity has been developed. The sensor shows remarkable fluorescence enhancement response for Al 3+ and Zn 2+ over a broad pH range with good anti-interference capability, which accompanied with an obvious color change easily detected by naked eyes. Sensor TS can detect as low as 3.7 × 10 −9 M for Al 3+ and 3.0 × 10 −8 M for Zn 2+ , whereas respective association constants are 1.16 × 10 4 M −1 and 2.08 × 10 4 M −1 . With the help of fluorescence titration and Job's plot, the stoichiometric ratio of TS with Al 3+ /Zn 2+ was determined to be 1:1. The sensing mechanism of sensor TS with Al 3+ /Zn 2+ based on the chelation-enhanced fluorescence (CHEF) was analyzed in detail through 1 H NMR titration, FTIR, HRMS and DFT studies . Moreover, sensor TS has been applied to the detection of Al 3+ and Zn 2+ in real environmental water and food samples as well as the filter paper-based test strips. Furthermore, sensor TS has good cell-permeability and can be used to selectively sense intracellular Al 3+ and Zn 2+ by bioimaging.
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ELECTROANALYSIS
·
2018
·Vol. 30
·期 11
·2768-2773
·
IF 2.851
Xin Feng,Xiaomei Dong,Qingcheng Zhang,Cuixia Cui,JingJing Zhang,Zhen Chen,Changmi Wu,Huile Jin,Shun Wang,Jichang Wang
In this study carbon materials with a hierarchical pore structure have been fabricated through a scalable and template free solvothermal method in the presence of metal catalysts, where the presence of metal catalysts was found to be essential for the initial polymerization process. The as-prepared carbon contained trace amounts of metal residues and exhibited highly efficient catalytic activity toward the oxygen reduction reaction (ORR). Among all the metal catalysts studied, cobalt containing porous carbon exhibited the highest ORR electrocatalytic activity with great tolerance to methanol crossover and excellent long-term cycling stability, outperforming the commercial 30 % ( w / w ) Pt/C catalysts. The great performance may be contributed to the unique porous structure, the large specific surface area of cobalt-doped carbon and chemical activity of cobalt. The result provides useful guidance for the development of carbon-based electrocatalysts.
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MATERIALS LETTERS
·
2018
·
IF 2.687
Ying Lei,Wensheng Gao,Yu Li,Rundong Wan,Wen Chen,Rui Zheng,Leiqiang Ma,Hongwei Zhou
In the present wok, a series of Ti-filled and Te-doped skutterudite compounds Ti x Co 4 Sb 11.5 Te 0.5 (x = 0.2, 0.3, 0.5) were successful fabricated by combination of microwave synthesis and spark plasma sintering technique. The microstructure and thermoelectric properties of Ti x Co 4 Sb 11.5 Te 0.5 bulks have been investigated systematically. The experimental results show that nearly single phase skutterudite were obtained by 5 min microwave synthesis. The Ti 0.3 Co 4 Sb 11.5 Te 0.5 bulk has smallest and uniform grain size of about 2 μm. The influences of Ti concentration on thermoelectric properties were discussed. A highest ZT of 0.60 for Ti 0.3 Co 4 Sb 11.5 Te 0.5 was achieved at 773 K along with a total thermal conductivity of 3.72 W m −1 K −1 , one might obtain higher values at a higher temperature.
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APPLIED SURFACE SCIENCE
·
2018
·
IF 4.439
Ying Xu,Shengnan Wang,Xiaoyan Hou,Zhe Sun,Yong Jiang,Zhongbing Dong,Quanbao Tao,Jun Man,Yan Cao
N, P, S co-doped graphene quantum dots (NPS-GQDs) were prepared via a one-step wet chemical plus dialysis method directly using anthracite coal as raw material. This facile oxidation process simultaneously synthesized graphene quantum dots (GQDs) and doped N, P and S atoms on edges or forming functional groups of GQDS. X-ray photoelectron spectroscopy (XPS) proved that the involved heteroatoms were successfully doped on GQDs. The local doping of N, P and S on GQDs can reach high levels as 5.6%, 3.7% and 3.7% (by atomic) during XPS detection, respectively. Raman spectra showed that the amount of defects or disorders of prepared GQDs increased during the transition of the coal hunk toward the nano-GQDs. The effect of graphitizing degree of applied coals (varied coal ranks) on the formation of GQDs implied that raw coals with too high or too low graphitizing degree were not optimizing for the formation of high-quality GQDs. The prepared NPS-GQDs showed excellent properties on the excitation-dependent fluorescence and the quench by some trace metals. Thus, the NPS-GQDs were applied to detect of Pb 2+ in both a DI water and a multi-elements analysis matrix, exhibited wide linear detection range (1–20 μM) and a detection limit of 0.75 μM.
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Journal of Materials Chemistry A
·
2018
·Vol. 6
·期 16
·7206-7220
·
IF 9.931
Tao Liang,Renzong Hu,Houpo Zhang,Hanyin Zhang,Hui Wang,Yunpeng Ouyang,Jun Liu,Lichun Yang,Min Zhu
A new ternary SnO2–Co–C composite is produced using a facile and scalable ball milling method, which has a microstructure that includes refined SnO2–Co hybrids embedded in graphite. The Co additives dramatically inhibit Sn coarsening in the lithiated SnO2, which enables highly reversible conversion reactions in the SnO2-based ternary composite during cycling. The electrodes exhibit high ICEs with an average of 80.8% and a reversible capacity of 780 mA h g−1 at 0.2 A g−1 after 400 cycles when the composite was manufactured via small planetary ball milling, and they achieve 875 mA h g−1 after 250 cycles when the material is prepared on a large-scale with a roller mill. Even at a high rate of 2 A g−1, the composite has a long lifetime and delivers 610 mA h g−1 after 1000 cycles. Furthermore, a stable capacity of 410 mA h g−1 can be also retained in a full cell combined with a LiFePO4 cathode and SnO2–Co–C anode when cycling within 2.3–3.4 V at 0.2C. The new ternary SnO2–Co–C composite demonstrates excellent comprehensive electrochemical performances, and it is a promising candidate anode material for use in practical applications.
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ACS Catalysis
·
2015
·
IF 9.312
Zhongzhe Wei,Jing Wang,Shanjun Mao,Diefeng Su,Haiyan Jin,Yihe Wang,Fan Xu,Haoran Li,Yong Wang
The earth-abundant nanohybrids Co0/Co3O4@N-doped carbon nanotubes were fabricated via an efficient thermal condensation of d-glucosamine hydrochloride, melamine, and Co(NO3)2·6H2O. The hybrids furnish excellent catalytic activity and perfect chemoselectivity (>99%) for a wide range of substituted nitroarenes (21 examples) under relatively mild conditions. The high catalytic performance and durability is attributed to the synergistic effects between each component, the unique structure of graphene layers-coated Co0, and the electronic activation of doped nitrogen. Density functional calculations indicate that the inner Co0 core and N species on the carbon shell can significantly decrease the dissociation energies of H2, giving evidence of the ability of carbon shell in the hybrids to enable H2 activation. These results open up an avenue to design more powerful low-cost catalysts for industrial applications.
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ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2015
·
IF 5.33
Qi Shen,Zuofeng Chen,Xiaofeng Huang,Meichuan Liu,Guohua Zhao
Carbon dioxide (CO2) reduction to useful chemicals is of great significance to global climate and energy supply. In this study, CO2 has been photoelectrocatalytically reduced to formate at metallic Cu nanoparticles (Cu NPs) decorated Co3O4 nanotube arrays (NTs) with high yield and high selectivity of nearly 100%. Noticeably, up to 6.75 mmol·L–1·cm–2 of formate was produced in an 8 h photoelectrochemical process, representing one of the highest yields among those in the literature. The results of scanning electron microscopy, transmission electron microscopy and photoelectrochemical characterization demonstrated that the enhanced production of formate was attributable to the self-supported Co3O4 NTs/Co structure and the interface band structure of Co3O4 NTs and metallic Cu NPs. Furthermore, a possible two-electron reduction mechanism on the selective PEC CO2 reduction to formate at the Cu–Co3O4 NTs was explored. The first electron reduction intermediate, CO2 ads•–, was adsorbed on Cu in the form of Cu–O. With the carbon atom suspended in solution, CO2 ads•– is readily protonated to form the HCOO– radical. And HCOO– as a product rapidly desorbs from the copper surface with a second electron transfer to the adsorbed species.
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JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
·
2014
·
IF 3.679
Jian Yu,Wan-Feng Lin,Le-Hui Leng,Shao-Kui Bao,Jian-Ping Zou,Xu-Biao Luo,De-Zhi Chen,Sheng-Lian Luo,Chak-Tong Au
Novel heterostructured TiO 2 /Co 4 S 4.23 Se 3.77 composites were synthesized by a combination of solid-state and sol–gel methods, and were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, and photocurrent measurements. The results of photocatalytic degradation of methylene blue over the as-prepared materials indicate that photocatalytic efficiency is closely related to the composition of the materials, and the 30%TiO 2 /Co 4 S 4.23 Se 3.77 catalyst exhibits the best adsorption and photodegradation efficiency under sunlight or visible-light irradiation. The adsorption capacity of 30%TiO 2 /Co 4 S 4.23 Se 3.77 for methylene blue is 18.59 mg/g calculated based on the Langmuir adsorption model. Adsorption kinetics studies show that the process fits well with a pseudo-second-order rate mechanism. Recycle experiments confirm that the 30%TiO 2 /Co 4 S 4.23 Se 3.77 catalyst is stable. The present work illustrates a new way for the design and syntheses of stable and high-efficiency catalysts applicable for the degradation of organic pollutants.
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