能源化学(英文版)

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Exploring the morphological effect of Ni_xMg_1-xO catalysts on CO₂ reforming of methane

Qinglin Xiao, Jiayu Xu, Jun Zhang, Yuhan Sun, Yan Zhu

2017, 26(3): 325-329. DOI: 10.1016/j.jechem.2017.03.010

摘要 ( 2484 )

To gain deep insight into the Morphological effect of Ni_xMg_1-xO catalysts on the reaction of CO₂ reforming with methane, we designed and fabricated three different spatial structural Ni_xMg_1-xO catalysts. These Ni_xMg_1-xO catalysts with specific models such as rod, sheet and sphere, exhibited various activity and stability in CO₂ reforming reaction. Herein Ni_xMg_1-xO nanorods displayed higher catalytic activity, in which methane conversion was up to 72% and CO₂ conversion was 64% at 670 ℃ with a space velocity of 79,200 mL/(g cat h), compared with nanosheet and nanosphere counterparts. Furthermore, both catalysts of Ni_xMg_1-xO nanorod and nanosheet showed a high resistance toward coke deposition and sintering of active sites in the process of CO₂ reforming of methane.

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Investigation of microstructures of ZnCo₂O₄ on bare Ni foam and Ni foam coated with graphene and their supercapacitors performance

Jinlong Lv, Tongxiang Liang, Meng Yang, Suzuki Ken, Miura Hideo

2017, 26(3): 330-335. DOI: 10.1016/j.jechem.2017.04.010

摘要 ( 2694 )

The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCo₂O₄ microspheres with short nanowires were formed on bare Ni foam by hydrothermal method, while large-scale ZnCo₂O₄ nanowires arrays homogeneously aligned and separated adequately on Ni foam coated with graphene. This ZnCo₂O₄ nanowire structure exhibited superior supercapacitors properties. The excellent supercapacitors were mainly attributed to the large specific surface and the porosity on the nanowires which promoted the electrons and ions transportation. In addition, graphene improved conductivity of substrate for current collecting.

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Synthesis of γ-MnOOH nanorods by successive ionic layer deposition method and their capacitive performance

Artem A. Lobinsky, Valeri P. Tolstoy

2017, 26(3): 336-339. DOI: 10.1016/j.jechem.2017.04.015

摘要 ( 3292 )

It was first shown in the present study that layers of manganite γ-MnOOH can be deposited on the surface of a substrate by its multiple successive treatment by the solutions of MnSO₄ and K₂S₂O₈ using the successive ionic layer deposition (SILD) technique. Their analysis was carried out by the XRD, XPS, FT-IR, SEM and EDX methods. It has shown that the synthesized layers are formed by aggregates of nanorods up to 80-100 nm in length and approximately 8-10 nm in diameter. A probable sequence of chemical reactions leading to the formation of a layer of the given morphology is suggested. Testing of performance of supercapacitors with nickel foam electrodes incorporating the γ-MnOOH layers in the 0.1 M KOH electrolyte at 1 A/g indicated the specific capacitance equal to 1120 F/g. After 1000 work cycles the observed degradation of this value was less than 3%.

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Oleic acid-treated synthesis of MnO@C with superior electrochemical properties

Jing Guo, Jiaojiao Liang, Chunyu Cui, Jianmin Ma

2017, 26(3): 340-345. DOI: 10.1016/j.jechem.2017.03.003

摘要 ( 3942 )

MnO@C nanocomposites are synthesized by annealing MnO microspheres treated with oleic acid as carbon source. The obtained MnO@C nanocomposites exhibit a discharge capacity of 1075 mAh/g for the initial cycle, and show the excellent cycling performance with a discharge capacity of 421 mAh/g after 100 cycles at a current density of 100 mA/g. The total specific capacity of MnO@C nanocomposites is higher than those of pure MnO microspheres in our experiments. Owing to the superior electrochemical behavior, the as-obtained MnO@C nanocomposites are potentially applied as next-generation anode material for lithium-ion batteries.

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Impact of organic interlayer anions on the CO₂ adsorption performance of Mg-Al layered double hydroxides derived mixed oxides

Qingqing Qin, Junya Wang, Tuantuan Zhou, Qianwen Zheng, Liang Huang, Yu Zhang, Peng Lu, Ahmad Umar, Benoît Louis, Qiang Wang

2017, 26(3): 346-353. DOI: 10.1016/j.jechem.2017.01.003

摘要 ( 2861 )

Herein we report a systematical investigation on the promoting effect of the carbon chain length of the intercalated carboxylic anions on the CO₂ capture performance of Mg-Al layer double hydroxides (LDHs). A series of organo-LDHs were successfully synthesized via co-precipitation and calcination-rehydration methods. All as-prepared samples were characterized by many techniques including XRD, ATR-FTIR, BET, and TGA. The XRD and ATR-FTIR studies indicated that organic anions were successfully intercalated into LDHs. The influence of some important parameters such as calcination temperature, adsorption temperature, and coating with (Li-Na-K)NO₃ molten salt was investigated. The results exhibited that when the number of carbon is greater than 10, the CO₂ capture capacity steadily increased with the increase in carbon number. After coating with 55 mol% (Li-Na-K)NO₃ molten salt, the CO₂ uptake of LDH-C16 sample with high Mg/Al ratios can be increased up to 3.25 mmol/g. The CO₂ adsorption/desorption cycling stability was also studied using temperature swing adsorption, which showed a stable CO₂ capture performance even after 22 cycles. Considering its high CO₂ capture capacity and good cycling stability, this novel CO₂ adsorbent is very promising in the sorption-enhanced water gas shift (SEWGS) processes.

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Highly selective methanol-to-olefin reaction on pyridine modified H-mordenite

Ting He, Guangjin Hou, Jinjing Li, Xianchun Liu, Shutao Xu, Xiuwen Han, Xinhe Bao

2017, 26(3): 354-358. DOI: 10.1016/j.jechem.2017.02.004

摘要 ( 3111 )

The effects of the acid site in main channels of MOR zeolites on their product selectivity and deactivation in the MTO (methanol to olefin) reactions were investigated. The catalytic analysis demonstrates that the pyridine modified MOR zeolite yielded high selectivity (>65.3%) of C₂=-C₄=, although the conversion dropped from 100% to 54%. Furthermore, both the catalytic lifetime of MOR and the stability of yielding the lower olefins were increased from less than 30 min to more than 120 min after the modification with pyridine. ¹H MAS NMR on MOR and modified MOR shows that the acid sites in main channel do not benefit the productivity of lower olefins and catalysts' lifetime. It can be concluded from ex-situ ¹³C CP MAS NMR that the deposit species during the MTO reaction depend on the pore sizes, and the formation of large alkyl aromatic species more likely occurs in the 12-ring main channels rather than the 8-ring side pocket.

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A new kinetic model for direct CO₂ hydrogenation to higher hydrocarbons on a precipitated iron catalyst: Effect of catalyst particle size

Ali Nakhaei Pour, Mohammad Reza Housaindokht

2017, 26(3): 359-367. DOI: 10.1016/j.jechem.2016.12.006

摘要 ( 3017 )

The kinetic of the direct CO₂ hydrogenation to higher hydrocarbons via Fischer-Tropsch synthesis (FTS) and reverse water-gas shift reaction (RWGS) mechanisms over a series of precipitated Fe/Cu/K catalysts with various particle sizes was studied in a well mixed, continuous spinning basket reactor. The iron catalysts promoted with copper and potassium were prepared via precipitation technique in various alcohol/water mixtures to achieve a series of catalyst particle sizes between 38 and 14 nm. A new kinetic model for direct CO₂ hydrogenation was developed with combination of kinetic model for FTS reaction and RWGS equilibrium condition. For estimate of structure sensitivity of indirect CO₂ hydrogenation to higher hydrocarbons, the kinetic parameters of developed model are evaluated for a series of iron catalysts with various particle sizes. For kinetic study a wide range of syngas conversions have been obtained by varying experimental conditions. The results show that the new developed model fits favorably with experimental data. The values of activation energies for indirect CO₂ hydrogenation reaction are fall within the narrow range of 23-16 kJ/mol.

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Effects of CeO₂ preparation methods on the catalytic performance of MoO₃/CeO₂ toward sulfur-resistant methanation

Dajun Meng, Baowei Wang, Zhen Liu, Weihan Wang, Zhenhua Li, Xinbin Ma

2017, 26(3): 368-372. DOI: 10.1016/j.jechem.2017.01.006

摘要 ( 2336 )

CeO₂ supports were prepared by calcination or precipitation method and 5% MoO₃/CeO₂ catalysts were prepared by incipient-wetness impregnation method. The catalytic performance of the 5% MoO₃/CeO₂ catalysts toward sulfur-resistant methanation was investigated. The results showed that the Mo/Ce-1 catalysts with CeO₂ support prepared by calcination method exhibited the best sulfur-resistant methanation activity and stability with CO conversion as high as 75% while the Mo/Ce-3 catalysts the poorest. The supports and catalysts were characterized by N₂-adsorption-desorption, temperature-programmed reduction (TPR), X-ray diffraction (XRD), Raman spectroscopy (RS) and scanning electron microscope (SEM). The results indicated that the saturated monolayer loading MoO₃ on Ce-3 support was lower than 5% and there were some crystalline MoO₃ particles on the surface of the Mo/Ce-3. The preparation method of CeO₂ had a big influence on the specific surface area, the crystalline of CeO₂, and the catalytic performance of the corresponding Mo-based catalyst for sulfur-resistant methanation.

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Bifunctionality of Cu/ZnO catalysts for alcohol-assisted low-temperature methanol synthesis from syngas: Effect of copper content

Ilho Kim, Gihoon Lee, Heondo Jeong, Jong Ho Park, Ji Chul Jung

2017, 26(3): 373-379. DOI: 10.1016/j.jechem.2017.02.003

摘要 ( 3124 )

Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO_X catalysts while varying the copper content (X). Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction intermediate in this reaction, creating a different reaction pathway. The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper, which is one of the main active sites for methanol synthesis. The acidic properties of the Cu/ZnO catalyst were also revealed as important factors, since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis. As a consequence, bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction. In this respect, the copper content (X) strongly affected the catalytic activity of the Cu/ZnO_X catalysts, and accordingly, the Cu/ZnO_0.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.

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Shaped binderless ZSM-11 zeolite catalyst prepared via a dry-gel conversion method: Characterization and application for alkylation of benzene with dimethyl ether

Wanshuo Zhang, Shuang Zhang, Wenjie Xin, Hui Liu, Yongchen Shang, Xiangxue Zhu, Shenglin Liu, Longya Xu

2017, 26(3): 380-389. DOI: 10.1016/j.jechem.2016.12.008

摘要 ( 3594 )

Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30SiO₂ mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best structure directing agent for the synthesis of the binderless ZSM-11 catalyst, without adding other alkaline materials. The 70HZSM-11/30SiO₂ mix serials materials crystallized for different times were detected by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy- energy dispersive spectroscopy (STEM-EDS) techniques, and so on. In order to investigate the possible crystallization mechanism, the textural and structural properties of 70HZSM-11/30SiO₂ mix serials samples were further characterized by N₂ adsorption-desorption. Acid properties were determined by temperature-programed desorption of NH₃ (NH₃-TPD) and pyridine adsorption-infrared (Py-IR) measurements. In the alkylation of benzene with dimethyl ether, the serials catalysts exhibited different benzene conversions. 70HZSM-11/30SiO₂ mix showed the lowest benzene conversion while sample 70HZSM- 11/30SiO₂ mix-6.5h synthesized only for 6.5h displayed a higher benzene conversion, even higher than the value over 70HZSM-11/30Al₂O₃ mix. Extending the crystallization time, the obtained samples displayed the increased benzene conversion in general under the same reaction conditions. In the end, the relation of physicochemical properties with the reaction performance was investigated.

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Enhanced hydrogen production activity over BiO_X-TiO₂ under solar irradiation: Improved charge transfer through bismuth oxide clusters

Police Anil Kumar Reddy, Chennaiahgari Manvitha, Pullagurala Venkata Laxma Reddy, Ki-Hyun Kim, Valluri Durga Kumari

2017, 26(3): 390-397. DOI: 10.1016/j.jechem.2016.12.007

摘要 ( 3118 )

A series of titania nanoparticles and nanotubes deposited with various quantities of bismuth (Bi) were prepared via sol-gel and hydrothermal methods, respectively. They were then characterized using X-ray diffraction spectroscopy (XRD), X-ray photo electron spectroscopy (XPS), UV-Vis diffused reflectance spectra (DRS), photoluminescence spectra (PLS), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), and BET surface analysis. These catalysts were employed for the photocatalytic production of hydrogen from a mixture of pure water and glycerol under solar light irradiation. The presence of the Bi^(3+x)+ species was found to play a vital role in enhancing activity while minimizing electron hole recombination (relative to bare TiO₂). The nanotubes exhibited better activity than the nanoparticles of Bi-deposited TiO₂, showing the significance of the morphology; however, photocatalytic activity is predominantly dependent on the deposition of bismuth. The activity increased by approximately an order of magnitude at the optimum concentration of Bi deposited over TiO₂ (2 wt%). The presence of the Bi^(3+x)+ species played a vital role in minimizing electron hole recombination, resulting in higher activity compared to bare TiO₂.

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A simple and distinguished nebulizer approach to prepare CdS thin films

M. Girish, R. Sivakumar, C. Sanjeeviraja, R. Gopalakrishnan

2017, 26(3): 398-405. DOI: 10.1016/j.jechem.2016.12.004

摘要 ( 2604 )

In this paper, we report the substrate temperature induced change in structural, optical, morphological, luminescence and photoelectrochemical properties of CdS films deposited by a simple and facile approach called nebulized spray pyrolysis technique. X-ray diffraction study confirmed the deposited CdS films belong to hexagonal wurtzite structure, with preferential orientation along c-axis, (002) direction perpendicular to the substrate plane. The crack free, uniform, and homogeneously distributed spherical particles are witnessed from AFM image. Various optical parameters like energy band gap, optical conductivity, refractive index, extinction coefficient, dielectric constants, and dispersion energy parameters of the films were evaluated. The strong band edge emission observed in the PL study may be attributed to the recombination of excitations and/or shallowly trapped electron-hole pairs. The first and second overtone of LO modes of CdS at 302 and 600 cm^-1 are observed in the Raman study. The photoelectrochemical properties of the films were also tested.

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The effect of FER zeolite acid sites in methanol-to-dimethyl-ether catalytic dehydration

Enrico Catizzone, Alfredo Aloise, Massimo Migliori, Girolamo Giordano

2017, 26(3): 406-415. DOI: 10.1016/j.jechem.2016.12.005

摘要 ( 4032 )

In this paper, the effect of acidity of zeolites with FER framework was studied in the methanol dehydration to dimethyl ether reaction, by comparing catalysts with different Si/Al ratios (namely 8, 30 and 60). The aim of this work was to investigate how the acid sites concentration, strength, distribution and typology (Brønsted and Lewis) affect methanol conversion, DME selectivity and coke formation. It was found that the aluminium content affects slightly acid sites strength whilst a relevant effect on acid sites concentration and distribution (Brønsted/Lewis) was observed as 24% of Lewis sites were found on Alrichest samples, whilst less than 10% of Lewis acid sites were observed on FER at higher Si/Al ratio. All the investigated catalyst samples showed a selectivity toward DME always greater than 0.9 and samples with the lowest Si/Al ratio exhibit the best performances in terms of methanol conversion, approaching the theoretical equilibrium value (around 0.85) at temperatures below 200 ℃. Turnover-frequency analysis suggests that this result seems to be related not only to the higher amount of acid sites but also that the presence of Lewis acid sites may play a significant role in converting methanol. On the other hand, the presence of Lewis acid sites, combined with a high acidity, promote the formation of by-products (mainly methane) and coke deposition during the reaction. As final evidence, all the investigated catalysts exhibit very high resistance to deactivation by coke deposition, over 60 h continuous test, and a GC-MS analysis of the coke deposited on the catalyst surface reveals tetra-methyl benzene as main component.

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Preparation, characterization and photocatalytic properties of BiOBr/ZnO composites

Yanling Geng, Na Li, Jiyan Ma, Zhenhai Sun

2017, 26(3): 416-421. DOI: 10.1016/j.jechem.2017.01.002

摘要 ( 3170 )

BiOBr/ZnO composite photocatalysts were prepared by a simple hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-Vis diffusion reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy, respectively. The photocatalytic activities were evaluated by the degradation of methyl blue (MB) under the simulated sunlight irradiation. Among all the samples, the BiOBr/ZnO composite with a mole ratio of 3:1 (Bi:Zn) exhibited the best photocatalytic activity. The improvement of photocatalytic activity was mainly attributed to the low recombination ratio of photo-induced electron-hole pairs. The possible photocatalytic mechanism was discussed on the basis of the band structures of BiOBr and ZnO.

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The influence of the type of N dopping on the performance of bifunctional N-doped ordered mesoporous carbon electrocatalysts in oxygen reduction and evolution reaction

Meng Li, Ziwu Liu, Fang Wang, Jinjin Xuan

2017, 26(3): 422-427. DOI: 10.1016/j.jechem.2017.01.004

摘要 ( 2731 )

To develop more ideal bifunctional heteroatom-doped carbon electrocatalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for regenerative fuel cells and rechargeable metal-air batteries, herein, tobacco-derived N-containing ordered mesoporous carbon (N-OMC) electrocatalysts with different N species distributions are designed. Results indicate that the as-prepared N-OMC with more pyrrolic and pyridinic Ns exhibits much higher activities for the ORR and OER than N-OMC with more graphitic N in both acidic and alkaline media, suggesting that the increase of pyrrolic and pyridinic Ns favors the improvement of ORR and OER activities of the N-containing carbon catalysts, and showing a great potential for the designing of more effective, lower-cost ORR and OER bifunctional electrocatalysts for future regenerative fuel cells and rechargeable metal-air batteries.

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Highly efficient Fe_xNi_1-xO_y/CP electrode prepared via simple soaking and heating treatments for electrocatalytic water oxidation

Yan Gao, Fengxia Wu, Hu Chen

2017, 26(3): 428-432. DOI: 10.1016/j.jechem.2016.12.009

摘要 ( 3586 )

The oxygen evolution reaction (OER) is a key step in the overall water splitting process. Numerous electrocatalysts have been developed to lower the overpotential and accelerate the kinetics of the OER. In this work, a simple soaking and heating treatment was used to form a stable and efficient Fe_xNi_1-xO_y/CP electrode. The electrode combined nickel and iron oxides on a commercial carbon paper were used for electrocatalytic water oxidation. The best Fe_xNi_1-xO_y/CP electrode (Ni/Fe=15/1) displayed a current density of 10 mA/cm² at a low overpotential of 290 mV in 0.1 M KOH solution with a Tafel slope of 52 mV/dec. A higher current density of ~50 mA/cm² at the same overpotential and a lower Tafel slope of 43 mV/dec was obtained for this electrode in 1.0 M KOH solution. Excellent durability of the Fe_xNi_1-xO_y/CP electrode in 1.0 M KOH solution was confirmed under a high current density of 136 mA/cm² at an overpotential of 340 mV.

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Mesoporous cadmium bismuth niobate (CdBi₂Nb₂O₉) nanospheres for hydrogen generation under visible light

Aniruddha K. Kulkarni, Yogesh A. Sethi, Rajendra P. Panmand, Latesh K. Nikam, Jin-Ook Baeg, N.R. Munirathnam, Anil V. Ghule, Bharat B. Kale

2017, 26(3): 433-439. DOI: 10.1016/j.jechem.2016.12.012

摘要 ( 2751 )

Herein, we report visible light active mesoporous cadmium bismuth niobate (CBN) nanospheres as a photocatalyst for hydrogen (H₂) generation from copious hydrogen sulfide (H₂S). CBN has been synthesized by solid state reaction (SSR) and also using combustion method (CM) at relatively lower temperatures. The as-synthesized materials were characterized using different techniques. X-ray diffraction analysis shows the formation of single phase orthorhombic CBN. Field emission scanning electron microscopy and high resolution-transmission electron microscopy showed the particle size in the range of ~0.5-1 μm for CBN obtained by SSR and 50-70 nm size nanospheres using CM, respectively. Interestingly, nanospheres of size 50-70 nm self assembled with 5-7 nm nanoparticles were observed in case of CBN prepared by CM. The optical properties were studied using UV-visible diffuse reflectance spectroscopy and showed band gap around ~3.0 eV for SSR and 3.1 eV for CM. The slight shift in band gap of CM is due to nanocrystalline nature of material. Considering the band gap in visible region, the photocatalytic activity of CBN for hydrogen production from H₂S has been performed under visible light. CBN prepared by CM has shown utmost hydrogen evolution i.e. 6912 μmol/h/0.5 g which is much higher than CBN prepared using SSR. The enhanced photocatalytic property can be attributed to the smaller particle size, crystalline nature, high surface area and mesoporous structure of CBN prepared by combustion method. The catalyst was found to be stable, active and can be utilized for water splitting.

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Photoelectrocatalytic activity of immobilized Yb doped WO₃ photocatalyst for degradation of methyl orange dye

S.V. Mohite, V.V. Ganbavle, K.Y. Rajpure

2017, 26(3): 440-447. DOI: 10.1016/j.jechem.2017.01.001

摘要 ( 2534 )

Pure WO₃ and Yb:WO₃ thin films have been synthesized by spray pyrolysis technique. Effect of Yb doping concentration on photoelectrochemical, structural, morphological and optical properties of thin films are studied. X-ray diffraction analysis shows that all thin films are polycrystalline nature and exhibit monoclinic crystal structure. The 3 at% Yb:WO₃ film shows superior photoelectrochemical (PEC) performance than that of pure WO₃ film and it shows maximum photocurrent density (I_ph=1090 μA/cm²) having onset potentials around + 0.3 V/SCE in 0.01 M HClO₄. The photoelectrocatalytic process is more effective than that of the photocatalytic process for degradation of methyl orange (MO) dye. Yb doping in WO₃ photocatalyst is greatly effective to degrade MO dye. The enhancement in photoelectrocatalytic activity is mainly due to the suppressing the recombination rate of photogenerated electron-hole pairs. The mineralization of MO dye in aqueous solution is studied by measuring chemical oxygen demand (COD) values.

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Edge-functionalized acetylene black anchoring sulfur for high-performance Li-S batteries

Wei Qin, Songtao Lu, Zhida Wang, Xiaohong Wu

2017, 26(3): 448-453. DOI: 10.1016/j.jechem.2016.11.021

摘要 ( 2748 )

To date, most of the research on electrodes for lithium sulfur batteries has been focused on the nanostructured sulfur cathodes and achieves significant success. However, from the viewpoint of manufacturers, the nanostructured sulfur cathodes are not so promising, because of the low volumetric energy density and high cost. In this work, we obtained the low-cost, scalable, eco-friendly mass production of edge-functionalized acetylene black-sulfur (FAB-S) composites by high-energy ball-milling technique for lithium sulfur batteries. The as-prepared FAB-S composite can deliver a high initial discharge capacity of 1304 mAh/g and still remain a reversible capacity of 814 mAh/g after 200 cycles at a charge-discharge rate of 0.2 C in the voltage range of 1.7-2.7 V. The observed excellent electrochemical properties demonstrate that the cathodes obtained by the facile high-energy ball-milling method as the cathode for rechargeable Li-S batteries are of great potential because it used the sole conductive additive acetylene black (AB). Such improved properties could be attributed to the partially exfoliation of AB, which not only keeps the AB's inherent advantage, but also increases the specific surface area and forms chemical bonds between carbon and sulfur, resulting in the accumulation of the polysulfides intermediate through both the physical and chemical routes.

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Synthesis of a PEBAX-1074/ZnO nanocomposite membrane with improved CO₂ separation performance

Navid Azizi, Toraj Mohammadi, Reza Mosayebi Behbahani

2017, 26(3): 454-465. DOI: 10.1016/j.jechem.2016.11.018

摘要 ( 3046 )

In this investigation, polymeric nanocomposite membranes (PNMs) were prepared via incorporating zinc oxide (ZnO) into poly (ether-block-amide)(PEBAX-1074) polymer matrix with different loadings. The neat membrane and nanocomposite membranes were prepared via solution casting and solution blending methods, respectively. The fabricated membranes were characterized by field emission scanning electron microscopy (FESEM) to survey cross-sectional morphologies and thermal gravimetric analysis (TGA) to study thermal stability. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) analyses were also employed to identify variations of the chemical bonds and crystal structure of the membranes, respectively. Permeation of pure gases, CO₂, CH₄ and N₂ through the prepared neat and nanocomposite membranes was studied at pressures of 3-18 bar and temperature of 25 ℃. The obtained results showed that the fabricated nanocomposite membranes exhibit better separation performance compared to the neat PEBAX membrane in terms of both permeability and selectivity. As an example, at temperature of 25 ℃ and pressure of 3 bar, CO₂ permeability, ideal CO₂/CH₄ and CO₂/N₂ selectivity values for the neat PEBAX membrane are 110.67 Barrer, 11.09 and 50.08, respectively, while those values are 152.27 Barrer, 13.52 and 62.15 for PEBAX/ZnO nanocomposite membrane containing 8 wt% ZnO.

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Hydrogen evolution kinetics on Ni cathodes modified by spontaneous deposition of Ag or Cu

Esteban A. Franceschini, Gabriela I. Lacconi, Horacio R. Corti

2017, 26(3): 466-475. DOI: 10.1016/j.jechem.2016.10.009

摘要 ( 2902 )

Nickel modification by spontaneous deposition of transition metals such as Ag and Cu is shown as an economic and simple alternative for the activation of hydrogen evolution reaction (HER) on cathodes in alkaline media. The kinetics of HER is studied on Ni/Ag and Ni/Cu catalysts by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) using a rotating disk electrode (RDE). Freshly synthesized catalysts, as well as catalysts subjected to a short chronoamperometric ageing procedure, are analyzed and the kinetic and thermodynamic parameters of the HER are obtained. The nickel surface modified with transition metals with an outer shell electronic configuration [xd¹⁰(x+1)s¹], such as Cu (3d¹⁰4s¹) and Ag (4d¹⁰5s¹), shows an improved activity for the HER compared to bare nickel. Furthermore, the Ni/Cu catalyst presents a decreased onset potential. The hydrogen evolution rate, measured as current density at -1.5 V (vs. SCE), is similar on Ni/Cu and Ni/Ag electrodes.

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Insights into electrolyte effects on photoactivities of dye-sensitized photoelectrochemical cells for water splitting

Xin Ding, Linlin Zhang, Yan Gao

2017, 26(3): 476-480. DOI: 10.1016/j.jechem.2016.11.022

摘要 ( 2796 )

Dye-sensitized photoelectrochemical cell (DS-PEC) is an especially attractive method to generate hydrogen via visible light driven water splitting. Electrolyte, an essential component of DS-PEC, plays a great role in determining the photoactivities of devices for water splitting. When using phosphate buffer (pH=6.4) as electrolyte, the DS-PEC displayed much higher photoactivity than using 0.1 M Na₂SO₄ (pH=6.4) as electrolyte. The insight is phosphate anion gathers together to form a negative electrostatic field on TiO₂ surface, which increases the resistance in the TiO₂/catalyst and electrolyte interface and validly reduces the charge recombination from TiO₂ to the oxidized catalyst.

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Amorphous Zr(OH)₄ coated LiNi_0.915Co_0.075Al_0.01O₂ cathode material with enhanced electrochemical performance for lithium ion batteries

Zhen Zhang, Pengfei Zhou, Huanju Meng, Chengcheng Chen, Fangyi Cheng, Zhanliang Tao, Jun Chen

2017, 26(3): 481-487. DOI: 10.1016/j.jechem.2016.12.003

摘要 ( 2779 )

LiNi_0.915Co_0.075Al_0.01O₂ (NCA) with Zr(OH)₄ coating is demonstrated as high performance cathode material for lithium ion batteries (LIBs). The coated materials are synthesized via a simple dry coating method of NCA with Zr(OH)₄ powders, and then characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Experimental results show that amorphous Zr(OH)₄ powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr(OH)₄ coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy (EIS) results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr(OH)₄ is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.

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Enhanced effect of plasma on catalytic reduction of CO₂ to CO with hydrogen over Au/CeO₂ at low temperature

Xiaobing Zhu, Jian-Hao Liu, Xiao-Song Li, Jing-Lin Liu, Xin Qu, Ai-Min Zhu

2017, 26(3): 488-493. DOI: 10.1016/j.jechem.2016.11.023

摘要 ( 2431 )

In terms of the reaction of CO₂ reduction to CO with hydrogen, CO₂ conversion is very low at low temperature due to the limitation of thermodynamic equilibrium (TE). To overcome this limitation, plasma catalytic reduction of CO₂ to CO in a catalyst-filled dielectric barrier discharge (DBD) reactor is studied. An enhanced effect of plasma on the reaction over Au/CeO₂ catalysts is observed. For both the conventionally catalytic (CC) and plasma catalytic (PC, P_in=15 W) reactions under conditions of 400 ℃, H₂/CO₂=1,200 SCCM, GHSV=12,000 mL·g^-1 cat·h^-1, CO₂ conversions over Au/CeO₂ reach 15.4% and 25.5% due to the presence of Au, respectively, however, those over CeO₂ are extremely low and negligible. Moreover, CO₂ conversion over Au/CeO₂ in the PC reaction exceeds 22.4% of the TE conversion. Surface intermediate species formed on the catalyst samples during the reactions are determined by in-situ temperatureprogrammed decomposition (TPD) technique. Interestingly, it disclosed that in the PC reaction, the formation of formate intermediate is enhanced by plasma, and the acceleration by plasma in the decomposition of formate species is much greater than that in the formation of formate species on Au/CeO₂. Enhancement factor is introduced to quantify the enhanced effect of plasma. Lower reactor temperature, higher gas hourly space velocity (GHSV), and lower molar ratio of H₂/CO₂ would be associated with larger enhancement factor.

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The design and fabrication of Co₃O₄/Co₃V₂O₈/Ni nanocomposites as high-performance anodes for Li-ion batteries

Yang Li, Lingbin Kong, Maocheng Liu, Weibin Zhang, Long Kang

2017, 26(3): 494-500. DOI: 10.1016/j.jechem.2016.11.017

摘要 ( 2833 )

The Co₃O₄/Co₃V₂O₈/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional (1D) Co₃O₄ nanowire arrays directly grew on Ni foam, whereas the 1D Co₃V₂O₈ nanowires adhered to parts of Co₃O₄ nanowires. Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network. As a result, the discharge capacity of Co₃O₄/Co₃V₂O₈/Ni nanocomposites could reach 1201.8 mAh/g after 100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g. Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such Co₃O₄/Co₃V₂O₈/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.

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Different oxidation routes for lattice oxygen recovery of double-perovskite type oxides LaSrFeCoO₆ as oxygen carriers for chemical looping steam methane reforming

Kun Zhao, Yang Shen, Zhen Huang, Fang He, Guoqiang Wei, Anqing Zheng, Haibin Li, Zengli Zhao

2017, 26(3): 501-509. DOI: 10.1016/j.jechem.2016.11.016

摘要 ( 2603 )

Double-perovskite type oxide LaSrFeCoO₆(LSFCO) was used as oxygen carrier for chemical looping steam methane reforming (CL-SMR) due to its unique structure and reactivity. Two different oxidation routes, steam-oxidation and steam-air-stepwise-oxidation, were applied to investigate the recovery behaviors of the lattice oxygen in the oxygen carrier. The characterizations of the oxide were determined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H₂-TPR) and scanning electron microscopy (SEM). The fresh sample LSFCO exhibits a monocrystalline perovskite structure with cubic symmetry and high crystallinity, except for a little impurity phase due to the antisite defect of Fe/Co disorder. The deconvolution distribution of XPS patterns indicated that Co, and Fe are predominantly in an oxidized state (Fe³⁺ and Fe²⁺) and (Co²⁺ and Co³⁺), while O 1s exists at three species of lattice oxygen, chemisorbed oxygen and physical adsorbed oxygen. The double perovskite structure and chemical composition recover to the original state after the steam and air oxidation, while the Co ion cannot incorporate into the double perovskite structure and thus form the CoO just via individual steam oxidation. In comparison to the two different oxidation routes, the sample obtained by steam-oxidation exhibits even higher CH₄ conversion, CO and H₂ selectivity and stronger hydrogen generation capacity.

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LSM-YSZ nano-composite cathode with YSZ interlayer for solid oxide fuel cells

Zhongbo Liu, Zhe Zhao, Lei Shang, Dingrong Ou, Daan Cui, Baofeng Tu, Mojie Cheng

2017, 26(3): 510-514. DOI: 10.1016/j.jechem.2016.11.019

摘要 ( 2584 )

Low temperature prepared (La_0.8Sr_0.2)_0.9MnO_3-δ-Y_0.15Zr_0.85O_1.93 (LSM-YSZ) nano-composite cathode has high three-phase boundary (TPB) density and shows higher oxygen reduction reaction (ORR) activity than traditional LSM-YSZ cathode at reduced temperatures. But the weak connection between cathode and electrolyte due to low sintering temperature restrains the performance of LSM-YSZ nano-composite cathode. A YSZ interlayer, consisted of nanoparticles smaller than 10 nm, is introduced by spinning coating hydrolyzed YSZ sol solution on electrolyte and sintering at 800 ℃. The thickness of the interlayer is about 150 nm. The YSZ interlayer intimately adheres to the electrolyte and shows obvious agglomeration with LSM-YSZ nano-composite cathode. The power densities of the cell with interlayer are 0.83, 0.46 and 0.21 W/cm² under 0.7 V at 800, 700 and 600 ℃, respectively, which are 36%, 48% and 50% improved than that of original cell. The interlayer introduction slightly increases the ohmic resistance but significantly decreases the polarization resistance. The depressed high frequency arcs of impedance spectra suggest that the oxygen incorporation kinetics are enhanced at the boundary of YSZ interlayer and LSM-YSZ nanocomposite cathode, contributing to improved electrochemical performance of the cell with interlayer.

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N-doped NaTaO₃ synthesize d from a hydrothermal method for photocatalytic water splitting under visible light irradiation

Che-Chia Hu, Hui-Hsin Huang, Yu-Chi Huang

2017, 26(3): 515-521. DOI: 10.1016/j.jechem.2016.12.002

摘要 ( 3405 )

NaTaO_3-xN_x catalysts were synthesized by a hydrothermal (H) and a solid-state (S) methods in this study. The H- and S-NaTaO_3-xN_x samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible (UV-vis) diffuse reflectance spectroscopy, and photoluminescence (PL) spectroscopy. The XRD patterns of the H- and S-samples showed peaks indexed to the pure phase of perovskite NaTaO₃ and minor peaks assignable to Ta₃N₅ at various synthesis temperatures. Substitution of oxygen by nitrogen ions causes the light absorption of the H- and S-NaTaO_3-xN_x samples to be extended to the 600-650 nm region, thus making the samples visible-light active. The NaTaO_3-xN_x samples exhibited photocatalytic activity for H₂ and O 2 evolution from aqueous methanol and silver nitrate solutions under visible-light irradiation. The UV-vis and PL spectra of the Hand S-catalysts revealed the presence of cationic vacancies and reduced metallic species, which acted as recombination centers. These results demonstrated that the preparation method plays a critical role in the formation of defect states, thereby governing the photocatalytic activity of the NaTaO_3-xN_x catalysts.

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Edge sulfurized graphene nanoplatelets via vacuum mechano-chemical reaction for lithium-sulfur batteries

Longlong Yan, Min Xiao, Shuanjin Wang, Dongmei Han, Yuezhong Meng

2017, 26(3): 522-529. DOI: 10.1016/j.jechem.2016.12.001

摘要 ( 2559 )

Lithium-sulfur batteries have great potential for high energy applications due to their high capacities, low cost and eco-friendliness. However, the particularly rapid capacity decay owing to the dissolution and diffusion of polysulfide intermediate into the electrolyte still hamper their practical applications. And the reported preparation procedures to sulfur based cathode materials are often complex, and hence are rather difficult to produce at large scale. Here, we report a simple mechano-chemical sulfurization methodology in vacuum environment applying ball-milling method combined both the chemical and physical interaction for the one-pot synthesis of edge-sulfurized grapheme nanoplatelets with 3D porous foam structure as cathode materials. The optimal sample of 70%S-GnPs-48 h (ball-milled 48 h) obtains 13.2 wt% sulfur that chemically bonded onto the edge of GnPs. And the assembled batteries exhibit high initial discharge capacities of 1089 mAh/g at 0.1 C and 950 mAh/g at 0.5 C, and retain a stable discharge capacity of 776 mAh/g after 250 cycles at 0.5 C with a high Coulombic efficiency of over 98%. The excellent performance is mainly attributed to the mechano-chemical interaction between sulfur and grapheme nanoplatelets. This definitely triggers the currently extensive research in lithium-sulfur battery area.

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Preparation of CO₂ selective composite membranes using Pebax/CuBTC/PEG-ran-PPG ternary system

Tayebeh Khosravi, Mohammadreza Omidkhah

2017, 26(3): 530-539. DOI: 10.1016/j.jechem.2016.10.013

摘要 ( 3070 )

Three phase Pebax^® MH 1657/PEG-ran-PPG/CuBTC (polymer/liquid/solid) was successfully deposited as a selective layer on a porous Polysulfone (PSF) support. In fact, the beneficial properties of PEG (high selectivity) with those of PPG (high permeability, amorphous) have been combined with superior properties of mixed matrix membrane (MMMs). The membranes were characterized by DSC, TGA and SEM, while CuBTC was characterized by CO₂ and CH₄ adsorption test. Statistically based experimental design (central composite design, CCD) was applied to analyze and optimize the effect of PEG-ran-PPG (10-50 wt%) and CuBTC (0-20 wt%) mass contents on the CO₂ permeance and CO₂/CH₄ ideal selectivity. Based on the regression coefficients of the obtained models, the CO₂ permeance was notably influenced by PEG-ran-PPG, while CuBTC has the most significant effect on the CO₂/CH₄ ideal selectivity. Under the optimum conditions (PEG-ran-PPG: 32.76 wt% and CuBTC: 20 wt%), nearly 620% increase in the CO₂ permeance and 43% enhancement in the CO₂/CH₄ ideal selectivity was observed compared to the neat Pebax. The effect of pressure (3, 9 and 15 bar) on the pure and mixed gas separation performance of the composite membranes was also investigated. The high solubility of CO₂ in the membranes resulted in the enhancement of CO₂ permeability with increase in gas pressure.

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Promoted effect of zinc-nickel bimetallic oxides supported on HZSM-5 catalysts in aromatization of methanol

Yanming Jia, Junwen Wang, Kan Zhang, Wei Feng, Shibin Liu, Chuanmin Ding, Ping Liu

2017, 26(3): 540-548. DOI: 10.1016/j.jechem.2016.10.014

摘要 ( 4125 )

Zn/ZSM-5 (NZ2) and Zn/Ni/ZSM-5 (NZ3) as the catalysts for methanol to aromatics (MTA) were synthesized by a simple ultrasonic impregnation. The textural and acid properties of all catalysts were characterized using XRD, HRTEM, NH₃-TPD, Py-IR, XPS, XRF and TG techniques. The XRD and HRTEM results showed that the basic zeolite structures were not affected much with the incorporation of Zn and Ni species. However, great changes have taken place in acid properties. The Py-IR and XPS results indicated that the Zn-Lewis acid sites (ZnOH⁺ species), which have stronger interaction with the zeolite framework compared with ZnO species, were generated at the expense of B acid sites with the incorporation of zinc species. Moreover, the product analysis results showed that the incorporation of zinc species promoted the primary aromatization by enhancing the dehydroaromatization and suppressing the cracking and subsequent H-transfer reaction. Furthermore, the addition of Ni species well inhibited the loss of zinc species by converting partial ZnO species to ZnOH⁺ species, and thus improved the aromatization activity and catalyst stability. The catalytic performance results showed that the NZ3 possess higher conversion of methanol in a longer time and lower average rate of coke formation compared with NZ2. In addition, the NZ3 also exhibited the highest yield of BTX as the reaction proceeds.

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Synthesis of cobalt-doped ZnO/rGO nanoparticles with visible-light photocatalytic activity through a cobalt-induced electrochemical method

Yuanquan Miao, Xuewen Wang, Wuyou Wang, Chengxi Zhou, Gang Feng, Jianxin Cai, Rongbin Zhang

2017, 26(3): 549-555. DOI: 10.1016/j.jechem.2016.10.017

摘要 ( 2967 )

ZnO is a semiconductor photocatalyst widely applied in photodegradation of organic pollutants and in photoelectric conversion. ZnO exhibits low photocatalytic activity due to poor absorption in the visible region. In this work, a novel cobalt-induced electrochemical growth method was developed to synthesize cobalt-doped ZnO/rGO nanoparticles in an aqueous solution at room temperature. Cobalt-doped ZnO/rGO nanoparticles exhibited wider visible-light absorption band ranging from 400 nm to 700 nm due to cobalt doping. The surface structure of ZnO formed by the cobalt-induced electrochemical method without other ions is suitable for photocatalytic reactions. The cobalt-doped ZnO/rGO nanoparticles were found to exhibit in photodegradation and photo-electrochemical measurements and exhibited enhanced photocatalytic activity under visible-light irradiation.

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Efficient one-pot synthesis of n-butyl levulinate from carbohydrates catalyzed by Fe₂(SO₄)₃

Ran An, Guizhuan Xu, Chun Chang, Jing Bai, Shuqi Fang

2017, 26(3): 556-563. DOI: 10.1016/j.jechem.2016.11.015

摘要 ( 2632 )

Butyl levulinate (BL) is a promising new candidate as diesel fuel and fuel additive. In this study, an efficient process for a one-pot synthesis of BL from biomass-derived carbohydrates in butanol medium with the catalysis of metal sulfates was developed. The catalytic activity of a series of metal sulfates for the synthesis of BL from fructose was investigated. Among various metal sulfates, ferric sulfate Fe₂(SO₄)₃ was found to be the most efficient catalyst, which gave a remarkably high BL yield of 62.8 mol% under the conditions of 463 K, 3 h, a catalyst dosage of 5.0 g/L, and fructose concentration of 25 g/L. Different carbohydrates including glucose, cellulose, inulin and sucrose were also used for one-pot synthesis of BL with the catalysis of Fe₂(SO₄)₃, showing the yields of 39.6, 30.5, 56.6 and 50.1 mol%, respectively. In addition, the recycling and reuse of Fe₂(SO₄)₃ was studied by characterizing them using powder X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS). A plausible reaction pathway for the one-pot synthesis of BL from fructose was proposed. This study provides a facile and feasible way for the synthesis of BL from biomass.

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Surfactant assisted solvothermal synthesis of LiFePO₄ nanorods for lithium-ion batteries

Yuan Gao, Ke Chen, Hongmei Chen, Xiaohua Hu, Zihua Deng, Zidong Wei

2017, 26(3): 564-568. DOI: 10.1016/j.jechem.2016.10.016

摘要 ( 2888 )

Well-shaped and uniformly dispersed LiFePO₄ nanorods with a length of 400-500 nm and a diameter of about 100 nm, are obtained with participation of a proper amount of anion surfactant sodium dodecyl sulfonate (SDS) without any further heating as a post-treatment. The surfactant acts as a self-assembling supermolecular template, which stimulated the crystallization of LiFePO₄ and directed the nanoparticles growing into nanorods between bilayers of surfactant (BOS). LiFePO₄ nanorods with the reducing crystal size along the b axis shorten the diffusion distance of Li⁺ extraction/insertion, and thus improve the electrochemical properties of LiFePO₄ nanorods. Such prepared LiFePO₄ nanorods exhibited excellent specific capacity and high rate capability with discharge capacity of 151 mAh/g, 122 mAh/g and 95 mAh/g at 0.1 C, 1 C and 5 C, respectively. Such excellent performance of LiFePO₄ nanorods is supposed to be ascribed to the fast Li⁺ diffusion velocity from reduced crystal size along the b axis and the well electrochemical conductivity. The structure, morphology and electrochemical performance of the samples were characterized by XRD, FE-SEM, HRTEM, charge/discharge tests, and EIS (electrochemical impedance spectra).

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Excellent electrocatalytic activity of benzil for direct reduction of CO₂ as well as indirect reduction of pyridine: A kinetic view of the electrocarboxylation process

Kobra Ghobadi, Hamid R. Zare, Hossein Khoshro, Abbas A. Jafari

2017, 26(3): 569-573. DOI: 10.1016/j.jechem.2016.09.002

摘要 ( 3343 )

Benzil, 1,2-diphenylethane-1,2-dione, was used as an excellent electrocatalyst for reduction of carbon dioxide, CO₂. The reduction overpotential of CO₂ was reduced about 900 mV in the presence of a benzil mediator. The chemical reaction of the product of the electrocatalytic reduction of CO₂, (activated CO₂, CO₂^·-) with pyridine at a glassy carbon electrode, GCE, surface and in an acetonitrile-But₄NClO₄ solution was investigated by cyclic voltammetry, chronoamperometry and controlled potential coulometry. By chronoamperometry, the catalytic rate constant, k, for the electron transfer between benzil and CO₂ was obtained as 8.1 ± 0.4 M^-1s^-1. The results indicate that pyridine has a strong interaction with the activated CO₂. The coulometry method was used to obtain the product of the pyridine chemical reaction with CO₂^·-. The spectral characterizations of FTIR, ¹H and ¹³C NMR of the coulometry experiment product proved that the pyridine anion radical, Py^·-, was carboxylated by CO₂^·-, and isonicotinic acid is the final major product.

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Catalytic performance of imidazole modified HZSM-5 for methanol to aromatics reaction

Haifeng Tian, Zhuangzhuang Zhang, Hui Chang, Xiaoxun Ma

2017, 26(3): 574-583. DOI: 10.1016/j.jechem.2017.03.008

摘要 ( 2959 )

A facile approach was developed for the preparation of nano-sized HZSM-5 with a hierarchical mesoporous structure by adding imidazole into conventional zeolite synthesis precursor solution. The physicochemical properties of modified HZSM-5 were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption isotherms, scanning electron microscopy (SEM), NH₃-temperature-programmed desorption (NH₃-TPD) and pyridine adsorption infrared spectroscopy (Py-IR). The coke in spent catalysts was characterized by thermogravimetry (TG). The results showed that hierarchical HZSM-5 zeolites with excellent textural properties, such as abundant porous structure, uniform particle size and suitable acidity, could be synthesized by the recipe of one-pot synthesis routes. Moreover, the obtained HZSM-5 exhibited higher selectivity of total aromatics as well as longer lifetime in the catalytic conversion of methanol to aromatics, comparing with conventional HZSM-5. It is expected that the synthesis approach demonstrated here will be applicable to other zeolites with particular textural properties and controllable particle sizes, facilitating the emergence of new-type porous materials and their related applications in catalysis and separation.

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Effect of hole-transporting materials on the photovoltaic performance and stability of all-ambient-processed perovskite solar cells

Nanaji Islavath, S Saroja, K Srinivas Reddy, P C Harikesh, G Veerappan, Shrikant V Joshi, Easwaramoorthi Ramasamy

2017, 26(3): 584-591. DOI: 10.1016/j.jechem.2016.12.011

摘要 ( 2459 )

High-efficiency perovskite solar cells (PSCs) reported hitherto have been mostly prepared in a moisture and oxygen-free glove-box atmosphere, which hampers upscaling and real-time performance assessment of this exciting photovoltaic technology. In this work, we have systematically studied the feasibility of allambient-processing of PSCs and evaluated their photovoltaic performance. It has been shown that phasepure crystalline tetragonal MAPbI₃ perovskite films are instantly formed in ambient air at room temperature by a two-step spin coating process, undermining the need for dry atmosphere and post-annealing. All-ambient-processed PSCs with a configuration of FTO/TiO₂/MAPbI₃/Spiro-OMeTAD/Au achieve opencircuit voltage (990 mV) and short-circuit current density (20.31 mA/cm²) comparable to those of best reported glove-box processed devices. Nevertheless, device power conversion efficiency is still constrained at 5% by the unusually low fill-factor of 0.25. Dark current-voltage characteristics reveal poor conductivity of hole-transporting layer caused by lack of oxidized spiro-OMeTAD species, resulting in high seriesresistance and decreased fill-factor. The study also establishes that the above limitations can be readily overcome by employing an inorganic p-type semiconductor, copper thiocyanate, as ambient-processable hole-transporting layer to yield a fill-factor of 0.54 and a power conversion efficiency of 7.19%. The present findings can have important implications in industrially viable fabrication of large-area PSCs.

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