能源化学(英文版)

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A series of conducting gel electrolytes for quasi-solid-state quantum dot-sensitized solar cells with boosted electron transfer processes

Qiming Yang, Wen Yang, Jialong Duan, Peizhi Yang

2018, 27(2): 335-342. DOI: 10.1016/j.jechem.2017.12.010

摘要 ( 1626 )

To pursue electron-generation stability with no sacrifice of photovoltaic performance has been a persistent objective for all kinds of solar cells. Here, we demonstrate the experimental realization of this objective by quasi-solid-state quantum dot-sensitized solar cells from a series of conducting gel electrolytes composed of polyacrylamide (PAAm) matrix and conductive polymers [polyaniline (PANi), polypyrrole (PPy) or polythiophene (PT)]. The reduction of S_x^2- occurred in both interface and three dimensional framework of conducting gel electrolyte as a result of the electrical conduction of PANi, PPy and PT toward refluxed electrons from external circuit to Pt electrode. The resulting solar cells can yield the solarto-electrical conversion efficiency of 2.33%, 2.25% and 1.80% for PANi, PPy and PT based gel electrolytes, respectively. Those solar cells possessed much higher efficiency than that of 1.74% based on pure PAAm gel electrolyte owing to the enhanced kinetics for S_x^2- ↔ S^2- conversion. More importantly, the stability of quasi-solid-state solar cell is significantly advanced, arising from the localization of liquid electrolyte into the three dimensional framework and therefore reduced leakage and volatilization.

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Energy-level dependent H₂O₂ production on metal-free, carbon-content tunable carbon nitride photocatalysts

Ruirui Wang, Xin Zhang, Fan Li, Ding Cao, Min Pu, Dandan Han, Junjiao Yang, Xu Xiang

2018, 27(2): 343-350. DOI: 10.1016/j.jechem.2017.12.014

摘要 ( 1444 )

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Light-driven production of H₂O₂ from water and molecular oxygen could be a promising way for obtaining both solar fuels and fundamental chemicals. During that process, the H₂O₂ yield is strongly dependent on the reaction pathway associated with two-electron reduction of dioxygen by the photo-generated electrons. Herein, we synthesized a series of metal-free, carbon-content tunable carbon nitride photocatalysts (named C₃N₄-Carbon) by a facile hydrothermal reaction and subsequent thermal treatment at appropriate temperatures. The energy levels of the C₃N₄-Carbon catalysts vary with the carbon doping level, which is conveniently tuned by changing the initial glucose concentration during the hydrothermal reaction. The surface carbon species evolve with the carbon content and the nitrogen atoms in the structure of carbon nitride are partially substituted by foreign carbon atoms based on XPS measurements. The optimal catalyst leads to the highest H₂O₂ yield of 1271 μmol L^-1 in an acidic aqueous solution (pH 3) after a reaction period of 4 h, twice higher than the pristine C₃N₄. In addition, the largest formation rate constant and the smallest decomposition rate constant of H₂O₂ are obtained on the optimal one according to the kinetics analyses. The decomposition tests of H₂O₂ indicate that the formation rate could be a dominant factor impacting the H₂O₂ yield. The conduction band position of the optimal catalyst is positively shifted to 0.06 V versus RHE, which is more favorable to the reduction of dioxygen to H₂O₂ (O₂/H₂O₂ at 0.69 V versus RHE). The positive shift of valence band also improves hole collection and leads to enhanced formation of H₂O₂.

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New carbazole based dyes as effective co-sensitizers for DSSCs sensitized with ruthenium (Ⅱ) complex (NCSU-10)

Praveen Naik, Rui Su, Mohamed R. Elmorsy, Ahmed El-Shafei, Airody Vasudeva Adhikari

2018, 27(2): 351-360. DOI: 10.1016/j.jechem.2017.12.013

摘要 ( 1265 )

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Herein, we report the design and synthesis of three new D-A type metal-free carbazole based dyes (S_1-3) as effective co-sensitizers for dye-sensitized solar cell (DSSC) sensitized with Ru(Ⅱ) complex (NCSU-10). In this new design, the electron rich carbazole unit was attached to three different electron withdrawing/anchoring species, viz. 4-amino benzoic acid, sulfanilic acid and barbituric acid. The dyes were characterized by spectral, photophysical and electrochemical analysis. Their optical and electrochemical parameters along with molecular geometries, optimized from DFT have been employed to apprehend the effect of the structures of these co-sensitizers on the photovoltaic performances. Further, S_1-3 dyes were co-sensitized along with a well-known NCSU-10 dye in order to broaden the spectral response of the co-sensitized devices and hence improve the efficiency. The photovoltaic performance studies indicated that, the device fabricated using S₁ dye as co-sensitizer with 0.2 mM of NCSU-10 exhibited improved PCE of 9.55% with J_SC of 22.85 mA cm^-2, V_OC of 0.672 V and FF of 62.2%, whereas the DSSC fabricated with dye NCSU-10 (0.2 mM) alone displayed PCE of 8.25% with J_SC of 20.41 mA cm^-2, V_OC of 0.667 V and FF of 60.6%. Furthermore, electronic excitations simulated using time-dependent DFT, were in good agreement with the experimentally obtained results of the co-sensitizers, indicating that the exchange-correlation function and basis set utilized for predicting the spectra of the co-sensitizers are quite appropriate for the calculations. In conclusion, the results showed the potential of simple organic co-sensitizers in the development of efficient DSSCs.

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Unveiling chain-chain interactions in CO₂-based crystalline stereocomplexed polycarbonates by solid-state NMR spectroscopy and DFT calculations

Zhenchao Zhao, Pengju Ren, Ye Liu, Kangbo Zhao, Xiao-Bing Lu, Weiping Zhang

2018, 27(2): 361-366. DOI: 10.1016/j.jechem.2017.12.016

摘要 ( 1327 )

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CO₂-based stereocomplexed polycarbonates derived from the intermolecularly interlocked interaction between the enantiopure polymers with the opposite configuration exhibit high crystallinity, excellent thermal and mechanical stabilities. Deep insights into the mechanism of stereocomplexation are of particular importance to the design and manufacture of new promising and sustainable polycarbonates with enhanced physicochemical properties. Our solid-state NMR experiments linking with DFT computations clearly reveal the specific chain-chain interactions in a typical stereocomplexed poly (4,4-dimethyl- 3,5,8-trioxabicyclo[5.1.0] octane carbonate) (PCXC). ¹³C CP/MAS NMR, ¹H DUMBO MAS NMR and ¹³C/¹H relaxation-time measurements indicate that the formation of stereocomplex reduces the local mobilities of carbonyl, methine and methylene groups in each chain of PCXC significantly. Through a combination of two-dimensional ¹H-¹³C HETCOR NMR and DFT calculation analysis, the cis-/trans- conformations and packing models of PCXC chains in the amorphous, enantionpure isotactic and stereocomplexed polycarbonates are identified. The splitting of ¹³C and ¹H NMR chemical shifts of methine groups in the backbone carbon region demonstrates the ordered interlock interactions between the R- and S- chain in the stereocomplexed PCXC.

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Achieving photocatalytic water oxidation on LaNbON₂ under visible light irradiation

Lipeng Wan, Feng-Qiang Xiong, Bingxue Zhang, Ruxin Che, Yue Li, Minghui Yang

2018, 27(2): 367-372. DOI: 10.1016/j.jechem.2018.01.004

摘要 ( 1237 )

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LaNbON₂ has narrow bandgap and wide visible-light absorption band, yet no photocatalytic water oxidation on LaNbON₂ has been reported. By a post-annealing treatment in Ar, anion vacancies were brought into LaNbON₂ as shown by EPR spectroscopy. These could act as donors in the semiconductor. And consequently the oxidative power of holes was enhanced as indicated by the difference between fermi level and valence band maximum (E_F-E_VBM) evaluated from valence band XPS. The annealed LaNbON₂ photocatalyst acquired water oxidation ability for the first time, which was improved by combining CoO_x as cocatalyst. Annealed LaNbON₂ derived from La₃NbO₇ had smaller particle size, higher concentration of anion vacancies, bigger E_F-E_VBM and better performance for photocatalytic oxygen evolution reaction than LaNbON₂ derived from LaNbO₄.

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Advanced metal sulfide anode for potassium ion batteries

Tao Li, Qiang Zhang

2018, 27(2): 373-374. DOI: 10.1016/j.jechem.2017.12.009

摘要 ( 1413 )

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Potassium-ion batteries (KIBs) are a promising alternative to lithium-ion batteries owning to the abundance of potassium on Earth and the relatively low K/K⁺ redox couple. To date, KIBs remains its infancy and the investigation of anode materials mainly focused on carbon-based materials, which deliver limited reversible capacity. Hence, it is imperative to explore alternative anode materials with high reversible capacity for KIBs. Recently, a pioneering work from Chen’s group reported a nanocomposite of Sb₂S₃ nanoparticles anchored on porous S,N-codoped graphene (denoted as Sb₂S₃-SNG) as an advanced anode material for KIBs, which exhibited remarkable enhancements of both capacity and cycling stability, highlighting the rational structure design of Sb₂S₃-SNG for maximum utilization of Sb₂S₃ nanoparticles and graphene layers for energy storage applications in high-performance KIBs.

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One-pot tandem conversion of fructose into biofuel components with in-situ generated catalyst system

Huai Liu, Xing Tang, Weiwei Hao, Xianhai Zeng, Yong Sun, Tingzhou Lei, Lu Lin

2018, 27(2): 375-380. DOI: 10.1016/j.jechem.2018.01.002

摘要 ( 1677 )

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In this contribution, one-pot tandem conversion of fructose into biofuel components, including 5- ethoxymethylfurfural (EMF), 2,5-(bis(ethoxymethyl)furan (BEMF) and ethyl levulinate (EL), was performed in an in-situ generated catalyst system through consecutive dehydration, etherification, and transfer hydrogenation. Specifically, ZrOCl₂ 8H₂O was in-situ decomposed into HCl and ZrO(OH)₂ in ethanol, which effectively catalyzed the dehydration/etherification of fructose to 5-ethoxymethylfurfural (EMF) and subsequent reductive etherification of EMF using ethanol as H-donor, respectively. EMF, BEMF and EL were detected as the main products, and total yield of detectable products of up to 65.4% was obtained at 200 ℃ in only 2 h.

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Highly efficient Cu/anatase TiO₂ {001}-nanosheets catalysts for methanol synthesis from CO₂

Yunfeng Bao, Chunlei Huang, Limin Chen, Yu dong Zhang, Long Liang, Jinjun Wen, Mingli Fu, Junliang Wu, Daiqi Ye

2018, 27(2): 381-388. DOI: 10.1016/j.jechem.2017.12.015

摘要 ( 1461 )

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Anatase TiO₂ nanosheets (-ns-) with dominant exposed {001} facets were used as support to load copper, and the synthesized Cu/TiO₂-ns catalysts were evaluated for CO₂ hydrogenation to methanol. Under the reaction conditions, P = 3.0 MPa, T = 260 ℃, V(N₂):V(H₂):V(CO₂) = 8:69:23 and gas hourly space velocity (GHSV) = 3600 mL g^-1 h^-1, the methanol yield reached an appealing high value, 5.6%. Copper-loading amount, calcination temperature and reduction atmosphere have been investigated in this work, which significantly influence the particle sizes of copper and/or the defect concentration in TiO₂, then leading to different catalytic performance. Characterizations of XRD, EPR, CO₂-TPD and FTIR demonstrate that higher specific surface area of Cu is good for the hydrogenation of CO₂ and adequate amount of Ti³⁺ plays important roles in CO₂ activation. Both of them facilitate high turnover frequency (TOF) of methanol formation.

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Surface-clean low-doped PdB/C as superior electrocatalysts toward ethanol oxidation in alkaline media

Yuan-Fang Wang, Chan Zhu, Yao-Yue Yang, Zhi-Gang Zhao

2018, 27(2): 389-394. DOI: 10.1016/j.jechem.2018.01.001

摘要 ( 1599 )

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Developing highly active, low-cost and organic surfactants-free Pd-based catalysts for ethanol oxidation reaction (EOR) is now critically important for direct ethanol fuel cells. Herein, surface-clean low-doped PdB/C catalysts (typically ca. 1.5 at% of B) are successfully prepared in an aqueous condition without adding any organic surfactants. TEM characterization shows that as-prepared low-doped PdB nanoparticles are evenly distributed on carbon support. Cyclic voltommagrams of as-prepared low-doped PdB/C in 0.5 M NaOH+ 1 M C₂H₅OH indicate that its onset oxidation potential of ethanol is ca. 80-120 mV more negative than that on commercial Pd/C. Meanwhile, the EOR mass activity of our home-made catalysts is up to 4018 mA mg^-1 Pd. Moreover, the durability on low-doped PdB/C catalysts is at most 2 times higher than that on commercial Pd/C. Geometric and electronic effects are adopted to understand the above mentioned enhancement of activity and durability. This work may provide a facile, low-cost and green strategy on preparing electrocatalysts toward EOR in alkaline media.

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Active sites contribution from nanostructured interface of palladium and cerium oxide with enhanced catalytic performance for alcohols oxidation in alkaline solution

Fulong Wang, Huaguang Yu, Zhiqun Tian, Huaiguo Xue, Ligang Feng

2018, 27(2): 395-403. DOI: 10.1016/j.jechem.2017.12.011

摘要 ( 1576 )

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Nanostructured interface is significant for the electrocatalysis process. Here we comparatively studied the electrooxidation of alcohols catalyzed by nanostructured palladium or palladium-cerium oxide. Two kinds of active sites were observed in palladium-cerium oxide system, attributing to the co-action of Pd-cerium oxide interface and Pd sites alone, by CO stripping technique, a structure-sensitive process generally employed to probe the active sites. Active sites resulting from the nanostructured interfacial contact of Pd and cerium oxide were confirmed by high resolution transmission electron microscopy and electrochemical CO stripping approaches. Electrochemical measurements of cyclic voltammetry and chronometry results demonstrated that Pd-cerium oxide catalysts exhibited much higher catalytic performances for alcohols oxidation than Pd alone in terms of activity, stability and anti-poisoning ability. The improved performance was probably attributed to the nanostructured active interface in which the catalytic ability from each component can be maximized through the synergistic action of bi-functional mechanism and electronic effect. The calculated catalytic efficiency of such active sites was many times higher than that of the Pd active sites alone. The present work showed the significance of valid nanostructured interface design and fabrication in the advanced catalysis system.

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Glycerol steam reforming over calcium hydroxyapatite supported cobalt and cobalt-cerium catalysts

J. Dobosz, M. Cichy, M. Zawadzki, T. Borowiecki

2018, 27(2): 404-412. DOI: 10.1016/j.jechem.2017.12.004

摘要 ( 1279 )

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Calcium hydroxyapatite (HAp) supported cobalt and cobalt-cerium catalysts were examined for hydrogen production in glycerol steam reforming. The catalysts were synthesized by incipient wetness impregnation method and characterized through X-ray diffraction, adsorption-desorption isotherms of N₂ and temperature-programmed reduction of H₂. Catalytic properties were examined in terms of glycerol conversion, selectivity toward hydrogen and C-containing products in temperature range of 650-800 ℃. The effect of active metal reduction and residence time (thereby flow feed rate) was analysed. It was found that the growth of residence time increased the hydrogen selectivity in the whole temperatures range whereas the catalyst reduction, before the catalytic process, decreased the hydrogen selectivity at temperatures lower than 750 ℃. The cerium addition improved the catalytic behaviour for hydrogen production via glycerol steam reforming. Cerium oxide suppressed the sintering of cobalt particles and as a result Co-Ce/HAp ensured higher stability and H₂ selectivity than Co/HAp. Under reaction conditions investigated in this study, the highest selectivity toward hydrogen at 650 ℃ was obtained for 7.5Co-Ce/HAp catalyst.

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DDQ as an effective p-type dopant for the hole-transport material X1 and its application in stable solid-state dye-sensitized solar cells

Yanyun Zhang, Xichuan Yang, Weihan Wang, Xiuna Wang, Licheng Sun

2018, 27(2): 413-418. DOI: 10.1016/j.jechem.2017.12.003

摘要 ( 1567 )

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X1 (MeO-TPD) is an inexpensive and easily synthesized π-conjugated molecule that has been used as a hole-transport material (HTM) in solid-state dye-sensitized solar cells (ssDSSCs), achieving relatively high efficiency. In this paper, we characterize the physicochemical properties of 2,3-dichloro-5,6-dicyano-1,4- benzoquinone (DDQ) and show that it is a promising p-dopant in a spin-coating solution with X1 as the HTM. The doped ssDSSCs showed an increase in short-circuit current density from 5.38 mA cm^-2 to 7.39 mA cm^-2, and their overall power conversion efficiency increased from 2.9% to 4.3%. Also, ssDSSCs with DDQ-doped X1 were more stable than the undoped samples, demonstrating that DDQ can act as a p-type dopant in X1 as an HTM for highly efficient, stable ssDSSCs.

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Significantly enhanced oxygen reduction activity of Cu/CuN_xC_y co-decorated ketjenblack catalyst for Al-air batteries

Fuzhi Li, Jingsha Li, Qiuju Feng, Jun Yan, Yougen Tang, Haiyan Wang

2018, 27(2): 419-425. DOI: 10.1016/j.jechem.2017.12.002

摘要 ( 1512 )

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Highly efficient and non-precious catalysts are imperative for oxygen reduction reaction (ORR) to replace Pt/C. Anchoring efficient active species to carbon supports is a promising and scalable strategy. Here we synthesize Cu nanoparticles and noncrystalline CuN_xC_y species co-decorated ketjenblack (KB) carbon catalyst (denoted as Cu-N-KB-acid) by a facile and scalable method using copper sulfate, melamine, and KB as raw materials. An initial one-pot hydrothermal treatment is designed before pyrolysis process to achieve the good distribution of Cu and melamine on KB via a possible chelation effect. Owing to the synergistic effect of Cu and CuN_xC_y on KB, this composite catalyst displays excellent ORR catalytic activity in alkaline solution, which is comparable to the commercial 20% Pt/C. When used as a catalyst in a home-made Al-air battery, it shows a stable discharge voltage of 1.47 V at a discharge density of 50 mA cm^-2, a little higher than that of Pt/C (1.45 V).

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Photovoltaic molecules based on vinylene-bridged oligothiophene applied for bulk-heterojunction organic solar cells

Jing Zhang, Pan Yin, Linjun Xu, Ping Shen, Mingfu Ye, Ningyi Yuan, Jianning Ding

2018, 27(2): 426-431. DOI: 10.1016/j.jechem.2017.12.001

摘要 ( 1390 )

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We have synthesized two photovoltaic molecules (HEX-3TVT-ID and EH-3TVT-ID) based on vinylenebridged oligothiophene applied as donor for the solution-processable bulk-heterojunction organic solar cells (OSCs). Vinylene unit was introduced as π-bridge in the oligothiophenes with 1,3-indenedione as end group and 4,4 -dihexyl-2,2' :5 ',2' -terthiophene or 3' ,4' -di(octan-3-yl)-2,2' :5' ,2' -terthiophene as core, respectively. Due to the different substituent positions of the alkyl group relative to the vinylene unit in the terthiophene, HEX-3TVT-ID and EH-3TVT-ID show different optical and electrochemical properties, corresponding to the photovoltaic performance of the OSCs devices. The power conversion efficiency (PCE) of the OSCs based on a blend of HEX-3TVT-ID and PC₇₁BM (1:0.8, weight ratio, 0.5% CN) reached 2.3%. In comparison, the OSCs based on the blend of EH-3TVT-ID and PC₇₁BM in the weight ratio of 1:1 without the additive show a higher PCE of 2.7%, with a typically high V_OC of 0.93 V, under the illumination of AM 1.5, 100 mW cm^-2.

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Active Fischer-Tropsch synthesis Fe-Cu-K/SiO₂ catalysts prepared by autocombustion method without a reduction step

Suthasinee Pengnarapat, Peipei Ai, Prasert Reubroycharoen, Tharapong Vitidsant, Yoshiharu Yoneyama, Noritatsu Tsubaki

2018, 27(2): 432-438. DOI: 10.1016/j.jechem.2017.11.029

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The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis (FTS) without a reduction step. The effect of different citric acid (CA):iron nitrate (N) molar ratios and acid types on the FTS performance of catalysts were investigated. The CA:N molar ratios had an important influence on the formation of iron active phases and FTS activity. The iron carbide (Fe_xC), which is known to be one of the iron active phases, was demonstrated by the X-ray diffraction and X-ray photoelectron spectroscopy. Increasing the CA:N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA:N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst (CA:N molar ratio = 0.1) achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to Fe_xC. But here, even if without reduction, Fe_xC was formed directly by autocombustion and induction period was eliminated during FTS reaction.

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Structural evolution of carbon aerogel microspheres by thermal treatment for high-power supercapacitors

Feng Li, Lijing Xie, Guohua Sun, Fangyuan Su, Qingqiang Kong, Yufang Cao, Xiangyun Guo, Chengmeng Chen

2018, 27(2): 439-446. DOI: 10.1016/j.jechem.2017.11.026

摘要 ( 1485 )

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In this work, a series of carbon aerogel microspheres (CAMs) with tailored pore structures were successfully prepared via a sol-gel method and subsequent heat-treatment at various temperatures from 600 to 1600 ℃. The effects of heat-treatment temperature (HTT) on the CAM microstructure were systematically investigated by physical and chemical characterization. The electrical conductivity increased by up to 250 S/cm and mesopores with high electrolyte accessibility developed in the CAM with increasing HTT. However, the specific surface area (SSA) decreased for HTTs from 1000 to 1600 ℃. The results show that these two factors should be finely balanced for further applications in high power supercapacitors. The CAMs carbonized at 1000 ℃ had the highest SSA (1454 m²/g), large mesoporous content (20%) and favorable conductivity (71 S/cm). They delivered a high energy density of 38.4 Wh/kg at a power density of 0.17 kW/kg. They retained an energy density of 25.5 Wh/kg even at a high power density of 10.2 kW/kg, and a good rate capability of 84% after 10,000 cycles. This performance is superior to, or at least comparable to, those of most reported carbon materials.

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Spray pyrolysis synthesis of nickel-rich layered cathodes LiNi_1-2xCo_xMn_xO₂ (x=0.075, 0.05, 0.025) for lithium-ion batteries

Yan Li, Xinhai Li, Zhixing Wang, Huajun Guo, Jiexi Wang

2018, 27(2): 447-450. DOI: 10.1016/j.jechem.2017.11.025

摘要 ( 1615 )

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In this study we report a series of nickel-rich layered cathodes LiNi_1-2xCo_xMn_xO₂ (x = 0.075, 0.05, 0.025) prepared from chlorides solution via ultrasonic spray pyrolysis. SEM images illustrate that the samples are submicron-sized particles and the particle sizes increase with the increase of Ni content. LiNi_0.85Co_0.075Mn_0.075O₂ delivers a discharge capacity of 174.9 mAh g^-1 with holding 93% reversible capacity at 1 C after 80 cycles, and can maintain a discharge capacity of 175.3 mAh g^-1 at 5 C rate. With increasing Ni content, the initial specific capacity increases while the cycling and rate performance degrades in some extent. These satisfying results demonstrate that spray pyrolysis is a powerful and efficient synthesis technology for producing Ni-rich layered cathode (Ni content > 80%).

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Sucrose pyrolysis assembling carbon nanotubes on graphite felt using for vanadium redox flow battery positive electrode

Haitao Yang, Chuanlin Fan, Qingshan Zhu

2018, 27(2): 451-454. DOI: 10.1016/j.jechem.2017.11.019

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In the present paper, multi-walled carbon nanotubes (MWCNTs) are successfully assembled on graphite felt (GF) using sucrose pyrolysis method for the first time. The in situ formed pyrolytic carbon is chosen as the binder because it is essentially carbon materials as well as CNTs and GF which has a natural tendency to achieve high bonding strength and low contact resistance. The MWCNTs/GF electrode is demonstrated to increase surface area, reduce polarization, lower charge transfer resistance and improve energy conversion efficiency comparing with GF. This excellent electrochemical performance is mainly ascribed to the high electro-catalytic activity of MWCNTs and increasing surface area.

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Effect of rubrene: P3HT bilayer on photovoltaic performance of perovskite solar cells with electrodeposited ZnO nanorods

Christian Mark Pelicano, Hisao Yanagi

2018, 27(2): 455-462. DOI: 10.1016/j.jechem.2017.11.018

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Improved photovoltaic performance of perovskite solar cells is demonstrated through the synergistic effect of electrodeposited ZnO nanorods and rubrene:P3HT bilayer as electron and hole-transporting layers, respectively. Highly crystalline ZnO nanorods were obtained by electrochemical deposition in a chloride medium. Additionally, rubrene interlayer was able to passivate or cover the grain boundaries of perovskite film effectively that led to reduced leakage current. A perovskite solar cell optimized with ZnO nanorods and rubrene:P3HT bilayer achieved a maximum efficiency of 4.9% showing reduced hysteresis behavior compared with the device having P3HT as the only hole-transporting layer. The application of longer nanorods led to better perovskite infiltration and shorter charge carrier path length. These results highlight the potential of electrodeposited ZnO nanorods and rubrene:P3HT bilayer as charge selective layers for efficient perovskite solar cells.

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Hierarchical graphite foil/CoNi₂S₄ flexible electrode with superior thermal conductivity for high-performance supercapacitors

Yunming Li, Jiahui Chen, Yaqiang Ji, Wenhu Yang, Xian-Zhu Fu, Rong Sun, Ching-Ping Wong

2018, 27(2): 463-471. DOI: 10.1016/j.jechem.2017.11.016

摘要 ( 1366 )

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Effective heat dissipation is a crucial issue in electrochemical energy storage devices. Thus, it is highly desirable to develop high-performance electrode materials with high thermal conductivity. Here, we report a facile one-step electrodeposition method to synthesize ternary cobalt nickel sulfide (CoNi₂S₄) flower-like nanosheets which are grown on graphite foil (GF) as binder-free electrode materials for supercapacitors. The as-fabricated GF/CoNi₂S₄ integrated electrode manifested an excellent thermal conductivity of 620.1 W·m^-1·K^-1 and a high specific capacitance of 881 F·g^-2 at 5 mA cm^-2, as well as good rate capability and cycling stability. Ultimately, the all-solid-state symmetric supercapacitor based on these advanced electrodes demonstrated superior heat dissipation performance during the galvanostatic charge-discharge processes. This novel strategy provides a new example of effective thermal management for potential applications in energy storage devices.

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One-step synthesis of graphitic-C₃N₄/ZnS composites for enhanced supercapacitor performance

Binbin Wei, Hanfeng Liang, Rongrong Wang, Dongfang Zhang, Zhengbing Qi, Zhoucheng Wang

2018, 27(2): 472-477. DOI: 10.1016/j.jechem.2017.11.015

摘要 ( 1501 )

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A series of graphitic-C₃N₄/ZnS (g-C₃N₄/ZnS) supercapacitor electrode materials have been prepared via a one-step calcination process of zinc acetate/thiourea with different mass ratios under nitrogen atmosphere. The optimized g-C₃N₄/ZnS composite shows a highest specific capacitance of 497.7 F/g at 1 A/g and good cycling stability with capacitance retention of 80.4% at 5 A/g after 1000 cycles. Moreover, gC₃N₄/ZnS composites display an improved supercapacitor performance in terms of specific capacitance compared to the pure g-C₃N₄ and ZnS. In addition, our designed symmetric supercapacitor device based on g-C₃N₄/ZnS composite electrodes can exhibit an energy density of 10.4 Wh/kg at a power density of 187.3 W/kg. As a result, g-C₃N₄/ZnS composites are expected to be a prospective material for supercapacitors and other energy storage applications.

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Hydrothermal synthesis of CoMoO₄/Co_1-xS hybrid on Ni foam for high-performance supercapacitors

Jinhua Ge, Jihuai Wu, Leqing Fan, Quanlin Bao, Jia Dong, Jinbiao Jia, Yaoqi Guo, Jianming Lin

2018, 27(2): 478-485. DOI: 10.1016/j.jechem.2017.11.014

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Cobalt molybdate/non-stoichiometric cobalt sulfide (CoMoO₄/Co_1-xS) hybrid was in situ grown on nickel foam by a simple two-step hydrothermal process. The as-prepared CoMoO₄/Co_1-xS hybrid electrode possessed core-shell nanostructure, large surface area and high specific capacitance of 2250 F g^-1 at a current density of 1 A g^-1. Using the hybrid as anode and activated carbon (AC) as cathode, an asymmetric supercapacitor of CoMoO₄/Co_1-xS//AC was fabricated. The optimized supercapacitor had large potential window of 1.6 V and high capacitance of 112 F g^-1, resulting in high power density of 804.5 W kg^-1 and energy density of 39.8 Wh kg^-1. Furthermore, the supercapacitor exhibited an excellent long cycle life along with 86.4% specific capacitance retained after 5000 cycles. The superior performances and good stability of the asymmetric supercapacitor can be attributed to the unique structure of the two components in hybrid, and the positive synergistic effects of the hybrid electrodes. The facile preparation process and excellent performance presented here render the CoMoO₄/Co_1-xS hybrid as a promising candidate for energy storage device.

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Pyrolysis mechanism of glucose and mannose: The formation of 5-hydroxymethyl furfural and furfural

Bin Hu, Qiang Lu, Xiaoyan Jiang, Xiaochen Dong, Minshu Cui, Changqing Dong, Yongping Yang

2018, 27(2): 486-501. DOI: 10.1016/j.jechem.2017.11.013

摘要 ( 1504 )

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Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural (5-HMF) and furfural (FF) are usually the two most important compounds derived from holocellulose. In this study, density functional theory (DFT) calculations are utilized to reveal the formation mechanisms and pathways of 5-HMF and FF from two hexose units of holocellulose, i.e., glucose and mannose. In addition, fast pyrolysis experiments of glucose and mannose are conducted to substantiate the computational results, and the orientation of 5-HMF and FF is determined by ¹³C-labeled glucoses. Experimental results indicate that C1 provides the aldehyde group in both 5-HMF and FF, and FF is mainly derived from C1 to C5 segment. According to the computational results, glucose and mannose have similar reaction pathways to form 5-HMF and FF with d-fructose (DF) and 3-deoxy-glucosone (3-DG) as the key intermediates. 5- HMF and FF are formed via competing pathways. The formation of 5-HMF is more competitive than that of FF, leading to higher yield of 5-HMF than FF from both hexoses. In addition, compared with glucose, mannose can form 5-HMF and FF via extra pathways because of the epimerization at C₂ position. Therefore, mannose pyrolysis results in higher yields of 5-HMF and FF than glucose pyrolysis.

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Highly efficient photocatalytic reduction of CO₂ and H₂O to CO and H₂ with a cobalt bipyridyl complex

Ya'nan Yao, Yan Gao, Lu Ye, Hu Chen, Licheng Sun

2018, 27(2): 502-506. DOI: 10.1016/j.jechem.2017.11.012

摘要 ( 1789 )

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The development of efficient molecular catalysts for visible-light driven CO₂ reduction, based on abundant materials, is necessary to meet energy demands and address environment problems. In this work, a Co(bpy)₂Cl₂ catalyst was developed and showed high efficiency and durability for the photocatalytic reduction of CO₂ and protons. Yields of CO and H₂ as high as 62.3 and 69.9 μmol were achieved and the turnover numbers (TONs) reached 6230 and 6990, respectively, under light irradiation (λ > 420 nm) for 4 h, indicating that the mixture gases could be a candidate as syngas. The apparent quantum yield was determined to be 2.1% for CO. Mechanistic studies revealed oxidative quenching of the photosensitizer Ru(bpy)₃Cl₂ by the catalyst. The photocatalytic performance, flexible synthesis and non-noble metal catalyst in our system show great promise for the practical application of Co(bpy)₂Cl₂ to photocatalytic reduction of CO₂.

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Architecture of Co-layered double hydroxide nanocages/graphene composite electrode with high electrochemical performance for supercapacitor

Xianyu Chu, Ting Deng, Wei Zhang, Dong Wang, Xiaofei Liu, Cai Zhang, Tingting Qin, Liyun Zhang, Bingsen Zhang, Chengmeng Chen, Weitao Zheng

2018, 27(2): 507-512. DOI: 10.1016/j.jechem.2017.11.011

摘要 ( 1454 )

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A facile hydrolysis method was applied to fabricate high-performance Co-layered double hydroxide (LDH) nanocages/graphene composites for supercapacitors. The materials exhibit enhanced rate capability than the counterpart electrode free of graphene while maintaining a high specific capacitance. In addition, such Co-LDH nanocages/graphene composites display an excellent cycling stability; the capacitance retention of Co-LDH nanocages/graphene composite electrode remains 90.4% after 10000 cycles at a current density of 2 A g^-1. The integration of high capacity of double hydroxide and outstanding conductivity of graphene makes the delicately-designed composites promising candidates for electrode materials for supercapacitors.

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Recent progresses in the suppression method based on the growth mechanism of lithium dendrite

Xiaolong Xu, Suijun Wang, Hao Wang, Chen Hu, Yi Jin, Jingbing Liu, Hui Yan

2018, 27(2): 513-527. DOI: 10.1016/j.jechem.2017.11.010

摘要 ( 1366 )

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Lithium secondary batteries (LSBs) with high energy densities need to be further developed for future applications in portable electronic devices, electric vehicles, hybrid electric vehicles and smart grids. Lithium metal is the most promising electrode for next-generation rechargeable batteries. However, the formation of lithium dendrite on the anode surface leads to serious safety concerns and low coulombic efficiency. Recently, researchers have made great efforts and significant progresses to solve these problems. Here we review the growth mechanism and suppression method of lithium dendrite for LSBs’ anode protection. We also establish the relationship between the growth mechanism and suppression method. The research direction for building better LSBs is given by comparing the advantages and disadvantages of these methods based on the growth mechanism.

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Electrochemical and electronic properties of nitrogen doped fullerene and its derivatives for lithium-ion battery applications

Parveen Sood, Ki Chul Kim, Seung Soon Jang

2018, 27(2): 528-534. DOI: 10.1016/j.jechem.2017.11.009

摘要 ( 1295 )

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We have studied the redox potentials and electronic properties of C₆₀ and C₅₉N using density functional theory method. It is found that doping C₆₀ with one nitrogen atom results in a slight increase in redox potential. Next, we have also studied C₅₉N functionalized with various redox-active oxygen containing functional groups and strongly electron withdrawing functional groups. It is found that the intrinsic electronic structure of the molecule is the major determinant of the redox potential. Our DFT calculations show that the electron affinity to redox potential of functionalized C₅₉N is correlated with the LUMO of the systems very well. This is the first systematic study on the redox properties and electronic structures of N-doped C₆₀ systems.

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Effect of steam-pretreatment combined with hydrogen peroxide on lignocellulosic agricultural wastes for bioethanol production: Analysis of derived sugars and other by-products

Alessandra Verardi, Alessandro Blasi, Tiziana Marino, Antonio Molino, Vincenza Calabrò

2018, 27(2): 535-543. DOI: 10.1016/j.jechem.2017.11.007

摘要 ( 1434 )

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The hydrogen peroxide, a green impregnating agent suitable for lignocellulosic biomass to bioethanol process, was used to pretreat sugarcane bagasse by steam explosion. Two different concentrations of hydrogen peroxide (0.2% and 1%) were investigated. Then, the biomass was hydrolyzed after pretreatment using cellulase. The amount released of: (i) cellobiose; (ii) monosaccharides, as glucose, xylose, arabinose and mannose and (iii) lignocellulose derived by-products, as furans and small organic acids (acetic, formic, and levulinic acid), was evaluated in the hydrolysate samples, previously pretreated both in the presence and absence of impregnating agent. By adding of hydrogen peroxide in steam-pretreatment, the average yield increase was 12% for glucose and as high as 34% for xylose, and cellobiose yield was decreased of about 30%. No significant increase has been observed in arabinose and mannose yield. Furthermore, the hydrogen peroxide seems not increased the formation of lignocellulose derived by-products during pretreatment process, with the exception of the levulinic acid.

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Three dimensional nano-LiMn_0.6Fe_0.4PO₄@C/CNT as cathode materials for high-rate lithium-ion batteries

Huan Zhang, Zhikai Wei, Jinjin Jiang, Lei Wang, Qi Wan, Tao Chen, Meizhen Qu, Mianzhong Chen

2018, 27(2): 544-551. DOI: 10.1016/j.jechem.2017.11.006

摘要 ( 1457 )

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Three dimensional (3D) nano-LiMn_0.6Fe_0.4PO₄@C/CNT composite was successfully synthesized by an oleylamine-assisted solvothermal method. The prepared composite showed excellent electrochemical performance, especially superior high rate capability. It could deliver a specific discharge capacity of 103.1 mAh/g, even at 80 C. The superior high rate performance of the as-prepared LiMn_0.6Fe_0.4PO₄@C/CNT electrode is attributed to its unique 3D conducting network: (1) the prepared LiMn_0.6Fe_0.4PO₄@C active particles were in nano-scale with a size of 30-50 nm; (2) LiMn_0.6Fe_0.4PO₄ nanoparticles were uniformly coated by amorphous carbon with a thickness of 3 nm; (3) the graphitized conductive CNTs were dispersed homogenously among the LiMn_0.6Fe_0.4PO₄@C active particles. The synergistic effect of the nanoscale amorphous carbon coated LiMn_0.6Fe_0.4PO₄@C active particles and the graphitized CNTs reduces the diffusion path of the lithium ions and benefits the transference ability of electron.

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Catalysis performance comparison of a Brønsted acid H₂SO₄ and a Lewis acid Al₂(SO₄)₃ in methyl levulinate production from biomass carbohydrates

Xueli Chen, Yuxuan Zhang, Tao Hou, Lujia Han, Weihua Xiao

2018, 27(2): 552-558. DOI: 10.1016/j.jechem.2017.11.005

摘要 ( 1388 )

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An experimental investigation was conducted to understand the roles of the Brønsted acid H₂SO₄ and Lewis acid Al₂(SO₄)₃ in methyl levulinate (ML) production from biomass carbohydrates, including glucose, fructose and cellulose. The product distributions with different catalysts revealed that the Lewis acid was responsible for the isomerization of methyl glucoside (MG), producing a significant amount of the subsequent product 5-methoxymethylfurfural (MMF), while the Brønsted acid facilitated the production of ML from MMF. Al₂(SO₄)₃ was efficient for monosaccharide conversion but not for cellulose. Using ball-milled cellulose with Al₂(SO₄)₃ resulted in a desired ML yield within a reasonable reaction time. The significant catalysis performances of two types of acids will guide the design of efficient catalytic processes for the selective conversion of biomass into levulinate esters.

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Surface-engineering of layered LiNi_0.815Co_0.15Al_0.035O₂ cathode material for high-energy and stable Li-ion batteries

Yugang Li, Haifeng Yu, Yanjie Hu, Hao Jiang, Chunzhong Li

2018, 27(2): 559-564. DOI: 10.1016/j.jechem.2017.11.004

摘要 ( 1375 )

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Surface engineering is an effective strategy to restrain the generation of rocksalt NiO phase on surface of layered LiNi_0.815Co_0.15Al_0.035O₂ (NCA) primary nanoparticles, a representative Ni-rich layered oxides cathode materials. Herein, we demonstrate the kilogram-scale synthesis of few-layer reduced graphene oxide (rGO) conformably coated NCA primary nanoparticles cathode materials by a mechanical wet ball-milling strategy. The lightening rGO coating layer effectively avoids the direct contact of electrolyte and NCA with rapid electrons transfer. As a result, the as-obtained NCA@rGO hybrids with only 1.0 wt% rGO content can deliver a high specific capacity (196 mAh g^-1 at 0.2 C) and fast charge/discharge capability (127 mAh g^-1 at 5 C), which is much higher than the corresponding NCA nanoparticles (95 mAh g^-1 at 5 C). Even after 100 cycles at 1 C, 91.7% of initial reversible capacity is still maintained. Furthermore, a prismatic pouch cell (240 mAh) is also successfully assembled with the commercial graphite anode.

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Sol-gel La₂O₃-ZrO₂ mixed oxide catalysts for biodiesel production

Daniela Salinas, Catherine Sepúlveda, Néstor Escalona, J. L. GFierro, Gina Pecchi

2018, 27(2): 565-572. DOI: 10.1016/j.jechem.2017.11.003

摘要 ( 1434 )

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Different La₂O₃ contents (0, 1, 2, 3, and 5 wt%) were used to prepared La₂O₃-ZrO₂ mixed oxides calcined at 600 ℃ by the sol-gel method. The catalytic activity was measured as biodiesel production from canola oil through a transesterification reaction. The characterization results indicate that the La₂O₃ monolayer formation and extent of basicity of m-ZrO₂ have a large influence on biodiesel production. Greater biodiesel conversion (56% at 4 h) was obtained with the 3% La₂O₃-ZrO₂ catalyst in the presence of basic sites and the formation of a monolayer of La₂O₃. The decrease in the catalytic activity for 5% La₂O₃-ZrO₂ resulted from the loss of active sites on the catalyst because of agglomeration, which was suggested by XPS and the isoelectric point. The kinetic data fit to a pseudo-first order constant, and the largest kinetic constant corresponds to 3% La₂O₃-ZrO₂, currently the largest heterogeneous non-alkaline metal catalyst reported for a transesterification reaction.

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Spherical FeF₃·0.33H₂O/MWCNTs nanocomposite with mesoporous structure as cathode material of sodium ion battery

Shuangying Wei, Xianyou Wang, Min Liu, Rui Zhang, Gang Wang, Hai Hu

2018, 27(2): 573-581. DOI: 10.1016/j.jechem.2017.10.032

摘要 ( 1490 )

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FeF₃·0.33H₂O crystallizes in hexagonal tungsten bronze structure with more opened hexagonal cavities are considered as next generation electrode materials of both lithium ion battery and sodium ion battery. In this paper the mesoporous spherical FeF₃·0.33H₂O/MWCNTs nanocomposite was successfully synthesized via a one-step solvothermal approach. Galvanostatic measurement showed that the performances of sodium ion batteries (SIBs) using FeF₃·0.33H₂O/MWCNTs as cathode material were highly dependent on the morphology and size of the as-prepared materials. Benefitting from the special mesoporous structure features, FeF₃·0.33H₂O/MWCNTs nanocomposite exhibits much better electrochemical performances in terms of initial discharge capacity (350.4 mAh g-1) and cycle performance (123.5 mAh g-1 after 50 cycles at 0.1 C range from 1.0 V to 4.0 V) as well as rate capacity (123.8 mAh g-1 after 25 cycles back to 0.1 C). The excellent electrochemical performance enhancement can be attributed to the synergistic effect of the mesoporous structure and the MWCNTs conductive network, which can effectively increase the contact area between the active materials and the electrolyte, shorten the Na⁺ diffusion pathway, buffer the volume change during cycling/discharge process and improve the structure stability of the FeF₃·0.33H₂O/MWCNTs nanocomposite.

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Introduction of table sugar as a soft second template in ZSM-5 nanocatalyst and its effect on product distribution and catalyst lifetime in methanol to gasoline conversion

Peyman Noor, Mohammadreza Khanmohammadi, Behrooz Roozbehani, Fereydoon Yaripour, Amir Bagheri Garmarudi

2018, 27(2): 582-590. DOI: 10.1016/j.jechem.2017.10.031

摘要 ( 1333 )

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Methanol to gasoline reaction was investigated on two prepared ZSM-5 catalysts. The first one was a conventional catalyst denoted as ZSM-5(C) and the other was a hierarchical catalyst-ZSM-5(S) which was prepared by incorporation of table sugar in catalyst gel during the synthesis procedure. The catalysts were characterized by FTIR, XRD, FE-SEM, N₂ adsorption-desorption, NH₃-TPD and TGA analytical technics. The proposed material showed pore modification as well as acidity moderating properties in ZSM-5 catalyst. The methanol to gasoline reaction was conducted in a fixed bed reactor with a WHSV of 1.5 h^-1. Methanol conversions, gasoline yield and selectivity in production for the synthesized catalysts were determined by gas chromatography method. The sugar modified catalyst converted more methanol than the conventional one and an enhancement in catalyst’s life time was observed. The selectivity to aromatics and durene were reduced compared to the conventional catalyst, so the gasoline quality was also further improved. The coking rate of catalysts was calculated employing TGA method. A reduction in coking rate and an increase in coke capacity of the modified catalyst were observed.

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Ultrathin nanosheets of cobalt-nickel hydroxides hetero-structure via electrodeposition and precursor adjustment with excellent performance for supercapacitor

Min Wei, Qingsong Huang, Yanping Zhou, Zhu Peng, Wei Chu

2018, 27(2): 591-599. DOI: 10.1016/j.jechem.2017.10.022

摘要 ( 1595 )

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A homogeneous better-dispersed ultrathin nanosheets (ca. 5 nm) of cobalt-nickel layered double hydroxides (LDH) supported on nickel foam scaffold was synthesized using controllable electrodeposition approach for high efficiency electrode materials of new supercapacitor. The morphology and electrochemical performances of the samples can be controlled by adjusting the precursor ratio, i.e., Ni(OAc)₂/Co(NO₃)₂ molar ratio in the electrodeposition approach. With the increase of this molar ratio, the electrochemical performances give a volcano trend. When the optimized molar ratio is 0.64/0.36, the hybrid delivered a high specific capacitance of 1587.5 F g^-1 at a current density of 0.5 A g^-1, with good rate capability (1155 F g^-1 was retained even at 10 A g^-1) and a robust recycle stability (remaining 91.5% after 1000 cycles at 5 A g^-1). The good performance could be attributed to the enlarged interlayer spacing, ultrathin nanosheets and synergistic effects between Co(OH)₂ and Ni(OH)₂. Furthermore, an asymmetric supercapacitor with a high energy density of 34.5 Wh kg^-1 at 425 W kg^-1 and excellent cycling stability of 85.4% after 5000 charge-discharge cycles at 2 A g^-1 was fabricated. We believe that this fantabulous new electrode material would have encouraging applications in electrochemical energy storage and a wide readership.

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MgFe hydrotalcites-derived layered structure iron molybdenum sulfide catalysts for eugenol hydrodeoxygenation to produce phenolic chemicals

Xinyong Diao, Na Ji, Mingyuan Zheng, Qingling Liu, Chunfeng Song, Yibo Huang, Qing Zhang, Alazar Alemayehu, Luoyun Zhang, Changhai Liang

2018, 27(2): 600-610. DOI: 10.1016/j.jechem.2017.07.008

摘要 ( 1361 )

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Hydrodeoxygenation (HDO) is an effective alternative to produce value-added chemicals and liquid fuels by removing oxygen from lignin-derived compounds. Sulfide catalysts have been proved to have good activity for the HDO and particularly high selectivity to phenolic products. Herein, we presented a novel way to prepare the layered structure sulfide catalysts (MgFeMo-S) derived from MgFe hydrotalcites via the intercalation of Mo in consideration of the memory effect of the calcined hydrotalcite. By varying the Mg/Fe mole ratio, a series of MgFeMo-S catalysts were successfully prepared and characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectrometer (ICP-OES). The characterization results indicated that the MgFeMo-S catalyst has retained the unique layered structure, which can facilitate uniform dispersion of the MoS₂ species on both the surface and interlayer of the catalysts. For the HDO of eugenol, the Mg₁Fe₂Mo-S catalysts exhibited the best HDO activity among all the catalysts due to its higher active metal contents and larger pore size. The HDO conversion was 99.6% and the yield of phenolics was 63.7%, under 5 MPa initial H₂ pressure (measured at RT) at 300 ℃ for 3 h. More importantly, MoS₂ species deposited on the interlayer galleries in the MgFeMo-S catalysts resulted in dramatically superior HDO activity to MoS₂/Mg₁Fe₂-S catalyst. Based on the mechanism investigation for eugenol, the HDO reaction route of eugenol under sulfide catalytic system has been proposed for the first time. Further applicability of the catalyst on HDO of more lignin-derived compounds was operated, which showed good HDO activity and selectivity to produce aromatic products.

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