? Journal of Energy Chemistry
Journal of Energy Chemistry
ISSN 1003-9953
     
能源化学(英文)

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PoCNTs: an efficient metal-free catalyst to convert n-butane

Prof. Su and coworkers reported an efficient Pmodified oCNT (PoCNT) catalyst for oxidative dehydrogenation (ODH) of n-butane on pages 349-353. The catalytic performance can be facilely optimized via tuning the phosphate loading amount, and the PoCNT catalyst with 0.8 wt% phosphate weight loading exhibits outstanding selectivity to n-butene. The effect of reaction conditions on the products distribution is systematically investigated and the catalytic mechanism of PoCNT catalyst for ODH of n-butane is also discussed in the paper. The obtained results will put forward to develop the metal-free catalyst for ODH of n-butane in industrial application.


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2016 Vol.25 No.3, Published: 2016-05-15
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COMMUNICATIONS
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New strategy to incorporate nano-particle sized water oxidation catalyst into dye-sensitized photoelectrochemical cell for water splitting
Peicheng Wei, Bo Hu, Li Zhou, Ting Su, Yong Na
2016 Vol. 25 (3): 345-348 [Abstract] ( 203 ) [HTML 1KB] [PDF] ( 0 )

In order to develop a new strategy to deposit nano-particle sized water oxidation catalyst based on earth abundant element to the photoanode in a photoelectrochemical cell for water splitting, Co3O4 as water oxidation catalyst was prepared and subsequently modified by 3-aminopropyltriethoxysilane. The amino functionalized Co3O4 catalyst was carefully characterized and then integrated to the ruthenium dye sensitized photoelectrode through fast Schiff base reaction. Cyclic voltammetry experiments in the dark confirmed that the modified Co3O4 catalyst was still active toward water oxidation, which could be initiated by oxidation of the ruthenium photosensitizer. Under visible light irradiation, incorporation of the modified Co3O4 catalyst resulted in dramatic enhancement of the transient photocurrent density for the photoanode, which was 8 times higher than that of without Co3O4 catalyst.

ARTICLES
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Phosphate modified carbon nanotubes for oxidative dehydrogenation of n-butane
Yajie Zhang, Rui Huang, Zhenbao Feng, Hongyang Liu, Chunfeng Shi, Junfeng Rong, Baoning Zong, Dangsheng Su
2016 Vol. 25 (3): 349-353 [Abstract] ( 224 ) [HTML 1KB] [PDF] ( 0 )

Catalytic performance of phosphate-modified carbon nanotube (PoCNT) catalysts for oxidative dehydrogenation (ODH) of n-butane has been systematically investigated. The PoCNT catalysts are characterized by SEM, TEM, XPS and TG techniques. We set the products selectivity as a function of butane conversion over various phosphate loading, and it is found that the PoCNT catalyst with the 0.8% phosphate weight loading (0.8PoCNT) exhibits the best catalytic performance. When the phosphate loading is higher than 0.8wt%, the difference of catalytic activity among the PoCNT catalysts is neglectable. Consequently, the ODH of n-butane over the 0.8PoCNT catalyst is particularly discussed via changing the reaction conditions including reaction temperatures, residence time and n-butane/O2 ratios. The interacting mechanism of phosphate with the oxygen functional groups on the CNT surface is also proposed.

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Development of high quality Fe3O4/rGO composited electrode for low energy water treatment
Ngoc Tuan Trinh, Sangho Chung, Jae Kwang Lee, Jaeyoung Lee
2016 Vol. 25 (3): 354-360 [Abstract] ( 205 ) [HTML 1KB] [PDF] ( 0 )

Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization (CDI) is promising as a future technology for water treatment. Graphene (rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly; hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5 V, which is 3 times higher than that of separate rGO electrodes. Thus this material is a promising candidate for water softening technology.

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Highly active and sintering-resistant heteroepitaxy of Au nanoparticles on ZnO nanowires for CO oxidation
Jiaxin Liu, Botao Qiao, Yian Song, Hailian Tang, Yudong Huang, Jingyue(Jimmy) Liu
2016 Vol. 25 (3): 361-370 [Abstract] ( 182 ) [HTML 1KB] [PDF] ( 0 )

Gold was supported on commercial ZnO powders (P) and homemade ZnO nanowires (NWs) by a modified deposition-precipitation method. X-ray diffraction and transmission electron microscopy investigation indicated that the size of the Au nanoparticles (NPs) depended strongly on the calcination temperature. The Au NPs were highly dispersed (< 5 nm) on both supports with calcination temperatures < 400℃. However, after calcination at 600℃ the Au NPs aggregated much more severely on ZnO P than on ZnO NWs. Gold NPs epitaxially grew into the {10-10} facets of the ZnO NWs after calcination at temperatures > 400℃. Such unique anchoring mechanism accounts for the much better experimentally observed sintering resistance. X-ray photoelectron spectra showed that Au existed as both metallic Au0 and Auδ+ species in all the synthesized catalysts with or without calcination treatment; the ratios of Auδ+/Au0, however, varied, depending on the treatment conditions. Catalytic tests showed that the activity for CO oxidation strongly depended on the size of the Au NPs. After calcination at 600℃, the specific rate for CO oxidation at room temperature decreased about 30 times on Au/ZnO P but only about 4 times on Au/ZnO NW. Stability tests demonstrated that the Au/ZnO NW catalysts had better stability for CO oxidation.

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Cadmium selenide-sensitized upright-standing mesoporous zinc oxide nanosheets for efficient photoelectrochemical H2 production
Jianwei Miao, Bin Liu
2016 Vol. 25 (3): 371-374 [Abstract] ( 181 ) [HTML 1KB] [PDF] ( 0 )

Cadmium selenide (CdSe)-sensitized upright-standing mesoporous zinc oxide (ZnO) nanosheets were prepared via a chemical bath deposition followed by annealing and electrochemical deposition of CdSe quantum dots (QDs). The CdSe QDs absorb visible photons under sunlight illumination, promoting electrons from the valence band to the conduction band of CdSe, which then quickly transfer to ZnO followed by the external load to the Pt counter electrode for water reduction. The as-prepared CdSe/ZnO nanosheets show promising photoelectrochemical activities for hydrogen generation.

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Catalytic activity and crystal structure modification of Pd/γ-Al2O3-TiO2 catalysts with different Al2O3 contents
Chengwu Yang, Qian Zhang, Jun Li, Ruirui Gao, Zhe Li, Wei Huang
2016 Vol. 25 (3): 375-380 [Abstract] ( 192 ) [HTML 1KB] [PDF] ( 0 )

Pd/γ-Al2O3-TiO2 catalysts containing various compositions of titania and alumina were prepared by sol-gel and wet-impregnation methods in attempt to study the particle size, nature of phases, morphology and structure of the composite samples. The ethanol oxidation experiments, N2 adsorption-desorption, FTIR, XRD and XPS were conducted, and the effects of Al2O3 content on the surface area, phase transformation and structural properties of TiO2 were investigated. The optimal value of ethanol conversion appeared on Pd/Al(0.05)-Ti and Pd/Al(0.90)-Ti catalysts irrespective of the ethanol oxidation temperature, and we call this as a double peaks phenomenon of catalytic activity. The XRD results reveal that the phase composition and crystallite size of the mixed oxides depend on Al2O3/TiO2 ratio and calcination temperature. Al2O3 can effectively prevent the agglomeration of TiO2 and this can be ascribed to the formation of Al-O-Ti chemical bonds in Al2O3-TiO2 crystals. Binding energy and Pd surface concentration of the catalysts were modified apparently, which may also lead to catalyst activity changes.

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p-Type CaFe2O4 semiconductor nanorods controllably synthesized by molten salt method
Xin Liu, Junzhe Jianga, Yushuai Jia, Ailing Jin, Xiangshu Chen, Fei Zhang, Hongxian Han
2016 Vol. 25 (3): 381-386 [Abstract] ( 193 ) [HTML 1KB] [PDF] ( 0 )

Pure phase, regular shape and well crystallized nanorods of p-type semiconductor CaFe2O4 have been fabricated for the first time by a facile molten salt assisted method, as confirmed by XRD, TEM, SEM and HRTEM. UV-vis diffuse reflectance spectra and Mott-Schottky plots show that the band structure of the CaFe2O4 nanorods is narrower than that of the CaFe2O4 nanoparticles synthesized by conventional method. The enhancement of the visible-light absorption is due to narrowness of the band gap in CaFe2O4 nanorods. The appropriate ratio between the molten salt and the CaFe2O4 precursors plays an important role in inhibiting the growth of the crystals along the (201) plane to give the desired nanorod morphology. This work not only demonstrates that highly pure p-type CaFe2O4 semiconductor with tunable band structure and morphology could be obtained using the molten salt strategy, but also affirms that the bandgap of a semiconductor may be tunable by monitoring the growth of a particular crystal plane. Furthermore, the facile eutectic molten salt method developed in this work may be further extended to fabricate some other semiconductor nanomaterials with a diversity of morphologies.

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Effects of ultrasonic impregnation combined with calcination in N2 atmosphere on the property of Co3O4/CeO2 composites for catalytic methane combustion
Hong Lu, Chengfa Jiang, Zhenwu Ding, Wei Wang, Wei Chu, Yanyan Feng
2016 Vol. 25 (3): 387-392 [Abstract] ( 192 ) [HTML 1KB] [PDF] ( 0 )

Co3O4/CeO2 composites with high surface areas and ultrafine crystalline sizes for catalytic combustion of methane were firstly prepared by a new sol-gel method which combined ultrasonic impregnation treatment and calcination in N2 atmosphere. The samples were characterized by various means such as nitrogen adsorption/desorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Results showed that the modified catalyst had the mesoporous structure, comparatively higher amount of surface oxygen and larger oxygen vacancies than others. As a result of the structure and surface composition merits, a high methane combustion conversion (50%) could be obtained at a low temperature of 262℃ for the modified Co3O4/CeO2 composites catalysts. The experimental results demonstrated that ultrasonic impregnation treatment combined with the N2 thermal treatment prior to calcination in air had a promising application for preparation of Co3O4/CeO2 composites catalysts for low-temperature catalytic combustion of methane.

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Ag/TiO2/freeze-dried graphene nanocomposite as a high performance photocatalyst under visible light irradiation
Ziaeddin Jafari, Nader Mokhtarian, Ghader Hosseinzadeh, Mousa Farhadian, Asghar Faghihi, Farideh Shojaie
2016 Vol. 25 (3): 393-402 [Abstract] ( 186 ) [HTML 1KB] [PDF] ( 0 )

Ag/TiO2/freeze-dried graphene nanocomposites have been prepared via a facile one-step solvothermal method for the photocatalytic degradation of RhB under visible light irradiation. During the solvothermal process, reduction of graphene oxide and loading of Ag/TiO2 nanoparticles on graphene sheets were achieved. Investigation of chemical state of products showed that covering of Ag/TiO2 surface with higher weight ratio of graphene resulting in that Ag metals in Ag/TiO2 were oxidized to Ag2O in nanocomposite structure after solvothermal process. Degree of photocatalytic activity enhancement strongly depends on the coverage of Ag/TiO2 surface by porous graphene. The sample of 1 wt% porous graphene hybridized Ag/TiO2 showed the highest photocatalytic activity, which is related to high migration efficiency of photoinduced of electrons and reduction of electron-hole recombination rate due to high electrical conductivity of graphene. Expanding of absorption to visible light region was ascribed to surface plasmon resonance effect of Ag metals and presence of graphene. Investigation of photocatalytic performance of formic acid as a dye-less organic pollutant showed that dye sensitization effect of RhB molecules during evaluation of photocatalytic performance was negligible.

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Biofuel cell based on horseradish peroxidase immobilized on copper sulfide as anode for decolorization of anthraquinone AV109 dye
Nataša Ž. Šekuljica, Milica M. Gvozdenović, Zorica D. Knežević-Jugović, Branimir Z. Jugović, Branimir N. Grgur
2016 Vol. 25 (3): 403-408 [Abstract] ( 170 ) [HTML 1KB] [PDF] ( 0 )

The potential application of electrochemically formed copper sulfide as horseradish peroxidase mediator in the enzymatic biofuel cell and anthraquinone AV109 dye as a fuel is investigated. The open circuit voltage of 0.52 V and short circuit current of ~3.6μA/cm2 are obtained, with the maximum specific power of ~1μW/cm2. The influence of internal resistance of the cell is discussed. Decolorization is investigated under open circuit potentials, and under external load of 3.3 kΩ conditions. In both cases, 40% of decolorization is achieved, but are three times faster under external load conditions. Specific energy during decolorization in such cell is estimated to ~5mWh/m2. The possible mechanism of the power generation during decolorization of AV 109 dye is discussed.

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Effect of SDS/THF on thermodynamic and kinetic properties of formation of hydrate from a mixture of gases (CH4+C2H6+C3H8) for storing gas as hydrate
Himangshu Kakati, Ajay Mandal, Sukumar Laik
2016 Vol. 25 (3): 409-417 [Abstract] ( 186 ) [HTML 1KB] [PDF] ( 0 )

In this work, the effect of sodium dodecyl sulfate (SDS) and combined effect of sodium dodecyl sulfate (SDS) and tetrahydrofuran (THF) on thermodynamic and kinetic properties of CH4+C2H6+C3H8 hydrate formation have been studied. Four different concentrations of sodium dodecyl sulfate (100 ppm, 500 ppm, 1000 ppm and 1500 ppm) have been used to see its effect on phase equilibrium condition and formation kinetics. Though sodium dodecyl sulfate (SDS) does not vary the pressure-temperature condition of hydrate formation, it has a prominent favorable effect on induction time, gas consumption, storage capacity and formation rate. The addition of 3% (mol) tetrahydrofuran (THF) to water+SDS system results in large shifts in phase equilibrium boundary to lower pressure and higher temperature. It has been noticed that the addition of tetrahydrofuran further enhances the formation rate. So the mixture of sodium dodecyl sulfate (SDS) and tetrahydrofuran (THF) can be effectively used as promoter for storing natural gas as hydrate.

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Effect of a second metal (Co, Fe, Mo and W) on performance of Ni2P/SiO2 for hydrodeoxygenation of methyl laurate
Zhengyi Pan, Rijie Wang, Ziyang Nie, Jixiang Chen
2016 Vol. 25 (3): 418-426 [Abstract] ( 173 ) [HTML 1KB] [PDF] ( 0 )

Ni2P/SiO2 and bimetallic NiMP/SiO2 (M=Co, Fe, Mo, W; Ni/M atomic ratio=5) catalysts were prepared by the temperature-programmed reduction method. The catalysts and their precursors were characterized by means of UV-Vis DRS, H2-TPR, XRD, TEM, CO chemisorption and NH3-TPD. Their performance for the deoxygenation of methyl laurate was tested on a fixed-bed reactor. The results show that the main phase was Ni2P in all catalysts, and M (M=Co, Fe, Mo, W) entered the lattice of Ni2P forming solid solution. Different from Fe and Co, the introduction of Mo and W into Ni2P/SiO2 reduced the phosphide particle size and increased the acid amount. In the deoxygenation reaction, the turnover frequency of methyl laurate increased on the catalysts in the order of NiMoP/SiO2, Ni2P/SiO2, NiWP/SiO2, NiFeP/SiO2 and NiCoP/SiO2, which is influenced by the size of phosphide particles and the interaction between Ni and M (M=Fe, Co, Mo or W). The introduction of the second metal (especially Mo and W) into Ni2P/SiO2 promoted the hydrodeoxygenation pathway. This is mainly attributed to the interaction between Ni and the second metal. Finally, the NiMoP/SiO2 catalyst was tested at 340℃, 3MPa, methyl laurate WHSV of 14 h-1 and H2/methyl laurate molar ratio of 25 for 132 h, and its deactivation took place. We found that the catalyst deactivation mainly resulted from carbonaceous deposit rather than the sintering of metal phosphide crystallites.

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In situ catalytic conversion of biomass fast pyrolysis vapors on HZSM-5
Yindi Zhang, Ping Chen, Hui Lou
2016 Vol. 25 (3): 427-433 [Abstract] ( 158 ) [HTML 1KB] [PDF] ( 0 )

In situ catalytic conversion of biomass fast pyrolysis vapors was carried out on HZSM-5 with varying Si/Al ratios (ranging from 20 to 300) at 450℃. The effects of Si/Al ratios of HZSM-5 zeolites on the distribution of biomass fast pyrolysis products and carbon deposits on catalysts were investigated. It was quite remarkable that after in situ catalytic conversion the amount of light phenols and hydrocarbons increased significantly while that of heavy phenols decreased a lot. Besides, the yield of cyclopentenones with relatively low oxygen content generally increased. It also indicated that as the Si/Al ratios of HZSM-5 increased, the amount of hydrocarbons and light phenols was found to drop greatly. The amount of carbon deposits was found to be around 8.5% with the exception of HZSM-5 with the Si/Al ratio of 300, which is much lower. Moreover, the carbon deposits yield dropped gradually with increasing Si/Al ratios of HZSM-5.Calcination of spent catalysts at 600℃ helped to restore the catalytic activity to a large extent despite a relatively lower efficiency of deoxygenation. Results indicated that HZSM-5 with relatively high acidity displayed great catalytic performance.

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Self-reducing bifunctional Ni-W/SBA-15 catalyst for cellulose hydrogenolysis to low carbon polyols
Zhuqian Xiao, Qiuwei Ge, Chuang Xing, Chengjun Jiang, Sheng Fang, Jianbing Ji, Jianwei Mao
2016 Vol. 25 (3): 434-444 [Abstract] ( 182 ) [HTML 1KB] [PDF] ( 0 )

A series of self-reducing bifunctional Ni-W/SBA-15 catalysts were synthesized using biomass-based carbon source as the reducing agent without conventional further reduction step. The self-reducing catalysts were performed on the hydrogenolysis of cellulose to low carbon polyols. The effects of calcination temperature and metallic loading contents for cellulose hydrogenolysis reaction were investigated detailedly. The optimal calcination temperature was found to be 673 K by TG analysis. The active metal nanoparticles with a better dispersion were observed using SEM and element mapping technology. The yield of low carbon polyols using the catalyst with the receipt of 10%Ni-15%W/SBA-15-673 K can reach as high as 68.14%, of which the ethylene glycol (EG) accounts for 61.04%.

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SnO2 nanospheres among GO and SWNTs networks as anode for enhanced lithium storage performances
Weiwei Wen, Mingzhong Zou, Qian Feng, Jiaxin Li, Heng Lai, Zhigao Huang
2016 Vol. 25 (3): 445-449 [Abstract] ( 171 ) [HTML 1KB] [PDF] ( 0 )

Conducting supporters of purified single-walled carbon nanotubes (SWNTs) and graphene oxide (GO) were used to confine pomegranate-structured SnO2 nanospheres for forming SnO2-GO-SWNT composites. As anode material for lithium ion batteries (LIBs), this composite exhibits a stable and large reversible capacity together with an excellent rate capability. In addition, an analysis of the AC impedance spectroscopy has been used to confirm the enhanced mechanism for LIB performance. The improved electrochemical performance should be ascribed greatly to the reinforced synergistic effects between GO and SWNT networks, and their enhanced contribution of the conductivity. These results indicate that this composite has potential for utilization in high-rate and durable LIBs.

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Preparation and characterization of Ag+ ion-exchanged zeolite-Matrimid®5218 mixed matrix membrane for CO2/CH4 separation
Abtin Ebadi Amooghin, Mohammadreza Omidkhah, Hamidreza Sanaeepur, Ali Kargari
2016 Vol. 25 (3): 450-462 [Abstract] ( 206 ) [HTML 1KB] [PDF] ( 0 )

In this work, the zeolite-Y was ion-exchanged by introducing silver cations into the framework of microsized nano-porous sodium zeolite-Y using a liquid-phase ion exchanged method. The Ag+ ion-exchanged zeolite, was then embedded into the Matrimid®5218 matrix to form novel mixed matrix membranes (MMMs). The particles and MMMs were characterized by ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), N2 adsorption-desorption isotherm, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Furthermore, the effects of filler content (0-20 wt%) on pure and mixed gas experiments, feed pressure (2-20 bar) and operating temperature (35-75℃) on CO2/CH4 transport properties of Matrimid/AgY MMMs were considered. Characterization results confirmed an appropriate ion-exchange treatment of the zeolites. The SEM results confirmed the superior interfacial adhesion between polymer and zeolites, particularly in the case of Matrimid/AgY membranes. This is due to the proper silverous zeolite/Matrimid functional groups' interactions. The gas permeation results showed that the CO2 permeability increased about 123%, from 8.34 Barrer for pure Matrimid to 18.62 Barrer for Matrimid/AgY (15 wt%). The CO2/CH4 selectivity was improved about 66%, from 36.3 for Matrimid to 60.1 for Matrimid/AgY (15 wt%). The privileged gas separation performance of Matrimid/AgY (15 wt%) was the result of a combined effect of facilitated transport mechanism of Ag+ ions as well as the intrinsic surface diffusion mechanism of Y-type zeolite. In order to survey the possibility of using the developed MMMs in industry, the CO2-induced plasticization effect and mixed gas experiment were accomplished. It was deduced that the fabricated MMMs could maintain the superior performance in actual operating conditions.

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A symmetric MnO2/MnO2 flexible solid state supercapacitor operating at 1.6 V with aqueous gel electrolyte
Nilesh R. Chodankar, Deepak P. Dubal, Girish S. Gund, Chandrakant D. Lokhande
2016 Vol. 25 (3): 463-471 [Abstract] ( 200 ) [HTML 1KB] [PDF] ( 0 )

The demand of microelectronic devices postulated high energetic flexible energy storage devices. Flexible solid state supercapacitor is flawless possible candidate to fulfill the requirement of microelectronic devices. This investigation provides practical evidence of the use of flexible solid state supercapacitors based on MnO2 electrodes with polyvinylpyrrolidone (PVP)-LiClO4 gel electrolyte. Initially, different acid mediated growths of MnO2 have been carried. Later, the electrochemical performances of MnO2 electrodes have been carried out. Impressively, the fabricated symmetric flexible solid state supercapacitor (FSS-SC) device demonstrates the highest operating potential window of 1.6 V with extended cycling stability. Moreover, the cell exhibits high energy density of 23 Wh/kg at power density of 1.9 kW/kg. It is interesting to note that the device shows excellent flexibility upon bending at angle of 180° for number of times. These results clearly evidenced those symmetric FSS-SC devices based on MnO2 electrodes are promising energy storage devices for microelectronic applications.

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Preparation and evaluation of crosslinked sulfonated polyphosphazene with poly(aryloxy cyclotriphosphazene) for proton exchange membrane
Yan Dong, Hulin Xu, Fengyan Fu, Changjin Zhu
2016 Vol. 25 (3): 472-480 [Abstract] ( 198 ) [HTML 1KB] [PDF] ( 0 )

Several crosslinked proton exchange membranes with high proton conductivities and low methanol permeability coefficients were prepared, based on the sulfonated poly[(4-fluorophenoxy)(phenoxy)] phosphazene (SPFPP) and newly synthesized water soluble sulfonated poly(cyclophosphazene) (SPCP) containing clustered flexible pendant sulfonic acids. The structure of SPCP was characterized by fourier transform infrared spectroscopy (FTIR) and 1H NMR spectra. The membranes showed moderate proton conductivities and much lower methanol permeability coefficients when compared to Nafion 117. Transmission electron microscopy (TEM) results indicated the well-defined phase separation between the locally and densely sulfonated units and hydrophobic units, which induced efficient proton conduction. In comparison with SPFPP membrane, the proton conductivities, oxidative stabilities and mechanical properties of crosslinked membranes remarkably were improved. The selectivity values of all the crosslinked membranes were also much higher than that of Nafion 117 (0.74×105 S. s/cm3). These results suggested that the cSPFPP/SPCP membranes were promising candidate materials for proton exchange membrane in direct methanol fuel cells.

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Higher open-circuit voltage set by cobalt redox shuttle in SnO2 nanofibers-sensitized CdTe quantum dot solar cells
Gautam E. Unni, Soorya Sasi, A. Sreekumaran Nair
2016 Vol. 25 (3): 481-488 [Abstract] ( 204 ) [HTML 1KB] [PDF] ( 0 )

In this study, we report an efficient CdTe-SnO2 quantum dot (QD) solar cell fabricated by heat-assisted drop-casting of hydrothermally synthesized CdTe QDs on electrospun SnO2 nanofibers. The as-prepared QDs and SnO2 nanofibers were characterized by dynamic light scattering (DLS), UV-Vis spectroscopy, photoluminescence (PL) spectra, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The SnO2 nanofibers deposited on fluorine-doped tin oxide (SnO2) and sensitized with the CdTe QDs were assembled into a solar cell by sandwiching against a platinum (Pt) counter electrode in presence of cobalt electrolyte. The efficiency of cells was investigated by anchoring QDs of varying sizes on SnO2. The best photovoltaic performance of an overall power conversion efficiency of 1.10%, an open-circuit voltage (Voc) of 0.80 V, and a photocurrent density (JSC) of 3.70mA/cm2 were obtained for cells with SnO2 thickness of 5-6μm and cell area of 0.25 cm2 under standard 1 Sun illumination (100 mW/cm2). The efficiency was investigated for the same systems under polysulfide electrolyte as well for a comparison.

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Improved photocatalytic activity of TiO2 produced by an alcohothermal approach through in-situ decomposition of NH4HCO3
Changyuan Hu, Chengjiang Lian, Shizheng Zheng, Xiaoyu Li, Tiewen Lu, Quanhong Hu, Shuwang Duo, Rongbin Zhang, Yingying Sun, Fei Chen
2016 Vol. 25 (3): 489-494 [Abstract] ( 208 ) [HTML 1KB] [PDF] ( 0 )

High crystallinity of TiO2 was prepared by a modified alcohothermal method, in which titanium isopropoxide was used as the titania precursor, absolute ethanol as the reaction medium, and NH4HCO3 as the raw materials for release of water, ammonia and carbon dioxides via in-situ decomposition. The X-ray powder diffraction (XRD) and transmission electron microscope (TEM) measurements showed that water and ammonia from the in-situ decomposition of NH4HCO3 played an important role in conducting the size, shape, crystallinity and microstructure of TiO2. The photoluminescence spectroscopy and photocurrent measurements indicated that enhanced crystallinity could hinder the recombination and promote the separation of electron-hole pairs in TiO2, which contribute to the improvement of photocatalytic activity. Methyl orange photodegradation under UV light confirmed that high crystallinity of TiO2 did present a high photocatalytic activity due to the effective separation of photoinduced charges.

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High performance of zinc-ferrum redox flow battery with Ac-/HAc buffer solution
Zhipeng Xie, Qi Su, Anhong Shi, Bin Yang, Baixiong Liu, Jianchai Chen, Xiaochun Zhou, Dingjian Cai, Liang Yang
2016 Vol. 25 (3): 495-499 [Abstract] ( 187 ) [HTML 1KB] [PDF] ( 0 )

A green low-cost redox flow battery using Zn/Zn2+ redox couple in HAc/NaAc medium and Fe2+/Fe3+ redox couple in H2SO4 medium was first proposed and investigated for potential stationary energy storage applications. The presence of HAc/NaAc in the negative electrolyte can keep the pH between 2.0 and 6.0 even when a large amount of H+ ions move into negative electrolyte from positive electrolyte through ion exchange membrane. In the pH range of 2.0-6.0, the chemical reaction of Zn species with H+ species is very insignificant; furthermore, the electroreduction of H+ ion on the negative electrode is significantly suppressed at this pH range. The zinc-ferrum redox flow battery (Zn/Fe RFB) operated within a voltage window of 0.5-2.0 V with a nearly 90% utilization ratio, and its energy efficiency is around 71.1% at room temperature. These results show that Zn/Fe RFB is a promising option as a stationary energy storage equipment.

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MoS3 loaded TiO2 nanoplates for photocatalytic water and carbon dioxide reduction
Wei Zhang, Tianhua Zhou, Jindui Hong, Rong Xu
2016 Vol. 25 (3): 500-506 [Abstract] ( 197 ) [HTML 1KB] [PDF] ( 0 )

Photocatalytic water splitting and carbon dioxide reduction provide us clean and sustainable energy resources. The carbon dioxide reduction is also the redemption of the greenhouse effect. MoS3/TiO2 photocatalysts based on TiO2 nanoplates have been synthesized via a hydrothermal acidification route for water and carbon dioxide reduction reactions. This facile approach generates well dispersed MoS3 with low crystallinity on the surface of TiO2 nanoplates. The as-synthesized MoS3/TiO2 photocatalyst showed considerable activity for both water reduction and carbon dioxide reduction. The thermal treatment effects of TiO2, the loading percentage of MoS3 and the crystalline phase of TiO2 have been investigated towards the photocatalytic performance. TiO2 nanoplate synthesized through hydrothermal reaction with the presence of HF acid is an ideal semiconductor material for the loading of MoS3 for photocatalytic water and carbon dioxide reduction simultaneously in EDTA sacrificial solution.

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Heterogeneous Cu2O-mediated ethylene glycol production from dimethyl oxalate
Lu Li, Dezhang Ren, Jun Fu, Yunjie Liu, Fangming Jin, Zhibao Huo
2016 Vol. 25 (3): 507-511 [Abstract] ( 167 ) [HTML 1KB] [PDF] ( 0 )

An efficient process for the conversion of dimethyl oxalateinto ethylene glycol with high selectivity and high yield over Cu2O was investigated. In situ formed Cu as a true catalytically active species showed a good catalytic performance for DMO conversion to produce EG in 95% yield.

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Preparation and characterization of In and Cu co-doped ZnS photocatalysts for hydrogen production under visible light irradiation
Melody Kimi, Leny Yuliati, Mustaffa Shamsuddin
2016 Vol. 25 (3): 512-516 [Abstract] ( 169 ) [HTML 1KB] [PDF] ( 0 )

In this work, a new photocatalyts In(0.1),Cu(x)-ZnS (x=0.01, 0.03, 0.05) is successfully synthesized using simple hydrothermal method. The physical and chemical properties of the In and Cu co-doped ZnS photocatalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), diffuse reflectance UV-visible spectroscopy (DR UV-visible) and photoluminescence spectroscopy (PL). The photocatalytic activity of the as-prepared In and Cu co-doped ZnS for hydrogen production from water with Na2SO3 and Na2S as sacrificial agent under visible light irradiation (λ ≥ 425 nm) was investigated. The presence of co-dopants facilitated the separation of electron-hole as well as increases the visible light absorption. The absorption edge of the co-doped ZnS photocatalyst shifted to longer wavelength as the amount of Cu increases. This indicates that the absorption properties depended on the amount of Cu doped. The photocatalytic activity of single doped In(0.1)-ZnS was significantly enhanced by co-doping with Cu under visible light irradiation. The highest photocatalytic activity was observed on In(0.1),Cu(0.03)-ZnS with the hydrogen production rate of 131.32μmol/h under visible light irradiation. This is almost 8 times higher than single doped In(0.1)-ZnS.

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Electroactive species study in the electrochemical reduction of CO2 in KHCO3 solution at elevated temperature
Heng Zhong, Katsushi Fujii, Yoshiaki Nakano
2016 Vol. 25 (3): 517-522 [Abstract] ( 178 ) [HTML 1KB] [PDF] ( 0 )

Photoelectrochemical and electrochemical reduction of CO2 into organic chemicals is promising for directly or indirectly transforming solar energy into chemical energy for further utilization. However, research on the electroactive species in these processes has been rather limited. In this work, we investigated possible electroactive species (CO2 or HCO3-) involved in the electrochemical reduction of KHCO3 at elevated temperatures without CO2 bubbling. The results showed that CO, CH4, and C2H4 were produced after electrochemical reduction of 3.0 mol/L KHCO3 at elevated temperature on a Cu electrode even without CO2 bubbling, although their faradaic efficiencies were low (< 6%). Measurements for CO2 generation from the decomposition of HCO3- showed that elevated temperature and high HCO3- concentration strongly promoted this process. These results suggested that the in-situ produced CO2 from the decomposition of HCO3- was probably the electroactive species in the electrochemical reduction of HCO3- without CO2 bubbling. Changes of the Gibbs free energy, rate constant, and activation energy of the decomposition of HCO3- into CO2 were also investigated and calculated from the experimental data.

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Efficient catalytic conversion of carbohydrates into 5-ethoxymethylfurfural over MIL-101-based sulfated porous coordination polymers
Xiaofang Liu, Hu Li, Hu Pan, Heng Zhang, Shan Huang, Kaili Yang, Wei Xue, Song Yang
2016 Vol. 25 (3): 523-530 [Abstract] ( 211 ) [HTML 1KB] [PDF] ( 0 )

In this work, a series of MIL-101-SO3H(x) polymeric materials were prepared and further used for the first time as efficient heterogeneous catalysts for the conversion of fructose-based carbohydrates into 5-ethoxymethylfurfural (EMF) in a renewable mixed solvent system consisting of ethanol and tetrahydrofuran (THF). The influence of -SO3H content on the acidity as well as on the catalytic activity of the porous coordination polymers in EMF production was also studied. High EMF yields of 67.7% and 54.2% could be successively obtained from fructose and inulin in the presence of MIL-101-SO3H (100) at 130℃ for 15h. The catalyst could be reused for five times without significant loss of its activity and the recovery process was facile and simple. This work provides a new platform by application of porous coordination polymers (PCPs) for the production of the potential liquid fuel molecule EMF from biomass in a sustainable solvent system.

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Fuel cell performance assessment for closed-loop renewable energy systems
Fabio V. Matera, Irene Gatto, Assunta Patti, Enza Passalacqua
2016 Vol. 25 (3): 531-538 [Abstract] ( 187 ) [HTML 1KB] [PDF] ( 0 )

Fuel cells and electrolysis are promising candidates for future energy production from renewable energy sources. Usually, polymer electrolyte fuel cell systems run on hydrogen and air, while the most of electrolysis systems vent out oxygen as unused by-product. Replacing air with pure oxygen, fuel cell electrochemical performance, durability and system efficiency can be significantly increased with a further overall system simplification and increased reliability. This work, which represents the initial step for pure H2/O2 polymer electrolyte fuel cell operation in closed-loop systems, focuses on performance validation of a single cell operating with pure H2/O2 under different relative humidity (RH) levels, reactants stoichiometry conditions and temperature. As a result of this study, the most convenient and appropriate operative conditions for a polymer electrolyte fuel cell stack integrated in a closed loop system were selected.

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Creating mesopores in ZSM-48 zeolite by alkali treatment: Enhanced catalyst for hydroisomerization of hexadecane
Miao Zhang, Lei Wang, Yujing Chen, Qiumin Zhang, Changhai Liang
2016 Vol. 25 (3): 539-544 [Abstract] ( 174 ) [HTML 1KB] [PDF] ( 0 )

ZSM-48 zeolites with various Si/Al ratios were hydrothermally synthesized in the H2N(CH2)6NH2 (HDA)-containing media. The obtained samples were highly crystallized with minor mixed phases as evidenced by X-ray powder diffraction (XRD). The alkaline treated ZSM-48 zeolites maintained its structure under different concentrations of NaOH aqueous solution. Micropores remained unchanged while mesopores with wide pore size distribution formed after the alkaline treatment. The surface area increased from 228 to 288m2/g. The Brönsted acid sites had little alteration while an obvious increase of Lewis acid sites was observed. The hydroisomerization of hexadecane was performed as the model reaction to test the effects of the alkali treatment. The conversion of hexadecane had almost no change, which was attributed to the preservation of the Brönsted acid sites. While high selectivity to iso-hexadecane with an improved iso to normal ratio of alkanes was due to the mesopore formation and improved diffusivity.

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Coking behaviors and kinetics on HZSM-5/SAPO-34 catalysts for conversion of ethanol to propylene
Ting Bai, Xin Zhang, Feng Wang, Wenting Qu, Xiling Liu, Chao Duan
2016 Vol. 25 (3): 545-552 [Abstract] ( 180 ) [HTML 1KB] [PDF] ( 0 )

The coke deposition on HZSM-5/SAPO-34 composite catalysts has been studied in the conversion of ethanol to propylene. The HZSM-5/SAPO-34 composite catalysts were synthesized by hydrothermal method (ZS-HS) and fully blending (ZS-MM). The used catalysts were characterized by XRD, N2 adsorption-desorption, TGA, TPO, elemental analysis, FTIR and XPS. The coking kinetics on both ZS-HS and ZS-MM has been investigated and their coking rate equations were obtained. The used ZS-MM catalyst had higher amount of coke and lower nC:nH than the used ZS-HS. 90% of the coke was deposited in the micropores of ZS-HS, while almost 45% of the coke located in the micropores of ZS-MM. The coke deposited on ZS-HS catalyst was mainly graphite-like carbon species, whereas dehydrogenated coke species was the major on ZS-MM. The coking activation energy of ZS-MM was lower than that of ZS-HS, and the coking rate on ZS-MM was faster than on ZS-HS. In addition, the regeneration of ZS-MM catalyst showed that it had a good hydrothermal stability. The differences on coking behaviors on the two catalysts were due to their different acidic properties and textures.

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Bimonthly
(Started in 1992)
Renamed from JNGC in 2013

ISSN 2095-4956
CN 21-1585/O4

Editors-in-Chief
Xinhe Bao
Gabriele Centi


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Journal of Energy Chemistry

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