Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species dur...Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.展开更多
Dear Editor,This letter presents a biocompatible cross-shaped magnetic soft robot and investigates its deformation mode control strategy through COMSOL modeling and simulation.Magnetic soft robots offer novel avenues ...Dear Editor,This letter presents a biocompatible cross-shaped magnetic soft robot and investigates its deformation mode control strategy through COMSOL modeling and simulation.Magnetic soft robots offer novel avenues for precise treatment within intricate regions of the human body.展开更多
The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously...The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously adjusting the p H instead of the traditional step-by-step method,which exhibited excellent performance in the catalytic oxidation of cyclopentene(CPE)to aldehydes or alcohols.The 93.69%CPE conversion and 97.15%total product selectivity(41.38%for glutaraldehyde(GA)and 55.77%for 1,2-cyclopentanediol(1,2-diol)were achieved by using H_(2)O_(2)as the oxidant and acetonitrile as the solvent.Through complementary characterization,it was found that the optimized di-lacunary silicotungstic polyoxometalate retained a complete Keggin structure,and exhibited better catalytic activity and stability than the mono-lacunary or saturated silicodecatungstate because it exposed more catalytic active centers.Furthermore,in situ FT-IR spectra was utilized to monitor the reaction process,revealing the formation of the active species W(O_(2))on the di-lacunary silicotungstic polyoxometalate and the intermediate epoxycyclopentane during the catalytic oxidation of cyclopentene.展开更多
Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen pe...Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.展开更多
Adsorbent regeneration is critical for a continuous adsorption–regeneration process and often underestimated. In this work,the regeneration of bifunctional AgXO@SBA-15 for [O]-induced reactive adsorptive desulfurizat...Adsorbent regeneration is critical for a continuous adsorption–regeneration process and often underestimated. In this work,the regeneration of bifunctional AgXO@SBA-15 for [O]-induced reactive adsorptive desulfurization of liquid fuel is reported and further investigated. The spent AgXO@SBA-15 was regenerated in various types of solvents followed by calcination and tested in multiple desulfurization–regeneration cycles. The effects of regenerate solvents were also compared systematically. The original and regenerated AgXO@SBA-15 was characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Nadsorption, X-ray photoelectron spectroscopy and atomic absorption spectrometry. The recovery of desulfurization capacity using various solvents follows the order of acetonitrile [ acetone [ ethanol [ methanol [ water. Owing to the complete reduction of silver species to Ag~0 and severe agglomeration of Ag~0, the bifunctional AgXO@SBA-15 demonstrating [ 85%(2.60 mg-S/g) of sulfur removal dramatically reduced to \ 46%(1.56 mg-S/g) after only 1 st-cycle regeneration. It is suggested that polar organic species strongly adsorbed(or residual) on the spent AgXO@SBA-15, in that case, after solvent wash may contribute to the accelerated decomposition of Ag~+ to Ag~0 in the following calcination step. The desulfurization capacity decreased rather mildly in the later regeneration runs. Cautious choice of regeneration conditions and strategies to rational design stabilized adsorbents is required to avert the adsorbent deactivation.展开更多
Lignin is an abundant renewable macromolecular material in nature,and degradation of lignin to improve its hydroxyl content is the key to its efficient use.Alkali lignin(AL)was treated with Brønsted acidic deep e...Lignin is an abundant renewable macromolecular material in nature,and degradation of lignin to improve its hydroxyl content is the key to its efficient use.Alkali lignin(AL)was treated with Brønsted acidic deep eutectic solvent(DES)based on choline chloride and p-toluenesulfonic acid at mild reaction temperature,the structure of the lignin before and after degradation,as well as the composition of small molecules of lignin were analyzed in order to investigate the chemical structure changes of lignin with DES treatment,and the degradation mechanism of lignin in this acidic DES was elucidated in this work.FTIR and NMR analyses demonstrated the selective cleavage of the lignin ether linkages in the degradation process,which was in line with the increased content of phenolic hydroxyl species.XPS revealed that the O/C atomic ratio of the regenerated lignin was lower than that of the AL sample,revealing that the lignin underwent decarbonylation during the DES treatment.Regenerated lignin with low molecular weight and narrow polydispersity index was obtained,and the average molecular weight(Mw)decreased from 17680 g/mol to 2792 g/mol(130°C,3 h)according to GPC analysis.The lignin-degraded products were mainly G-type phenolics and ketones,and small number of aldehydes were also generated,the possible degradation pathway of lignin in this acidic DES was proposed.展开更多
The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary c...The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary combination of X-ray power diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), pyridine-IR spectroscopy and N2 adsorption–desorption isotherms. The analyses showed that the nitridation didn’t destroy the crystallinity and specific surface area of zeolites, and the acidity of zeolites can be tailored by tuning the time of nitridation, resulting in the different concentration ratios of Br?nsted-to-Lewis(B/L) acid sites. Moreover, the nitrided zeolites exhibited high selectivity to 2-benzyl-1,3,5-trimethylbenzene than parent silica pillared MFI zeolite nanosheets in benzylation of mesitylene with benzyl alcohol. A balance between Br?nsted acid sites and Lewis acid sites can inhibit the self-etherification of benzyl alcohol and enhance the selectivity of alkylated product. These experimental data implied that nitridation was an effective method to modulate the acidity of zeolites and the synergy between Br?nsted acid sites and Lewis acid sites was a decisive factor to determine the selectivity.展开更多
Platinum and zinc containing LTA zeolite catalysts with tunable meso/microporosity were prepared by using ligand-metal precursors under hydrothermal condition. These materials were employed for oxidation of ethane to ...Platinum and zinc containing LTA zeolite catalysts with tunable meso/microporosity were prepared by using ligand-metal precursors under hydrothermal condition. These materials were employed for oxidation of ethane to oxygenates using hydrogen peroxides as oxidant under mild reaction condition. The results showed that platinum and zinc loaded LTA zeolites were effective for the partial oxidation of ethane with hydrogen peroxide giving the desired C_2 oxygenates. Moreover, the C_1 oxygenates were also obtained through subsequent C–C bond scission pathways. The over oxidation of ethanol/methanol to acetic acid/formic acid could be inhibited through the introduction of mesoporosity in LTA zeolites. Our findings for oxidation of ethane suggested that the selectivity to the oxidation products such as alcohols and acids could be tailored by tuning the metal species within the LTA zeolites and porosity of catalysts, indicating that a balance between the meso/microporosity and metal species in LTA zeolites can be realized for desirable catalysis by one-pot synthesis of zeolites. In addition, the selectivity to oxygenates can also be tuned by control of the reaction conditions, i.e. concentration of hydrogen peroxide or reaction time.展开更多
The stereo vision results from the interaction between geometrical optics and visual psychology.Large depth will bring discomforts for the results of ghosting and flicker.The relevance of the ratio of jumping out dept...The stereo vision results from the interaction between geometrical optics and visual psychology.Large depth will bring discomforts for the results of ghosting and flicker.The relevance of the ratio of jumping out depth(RJD)and electroencephalogram(EEG)gravity frequency(GF)was explored to re flect human health under di®erent three-dimensional(3D)depth information(mainly the negative disparity)displayed on a three-dimensional television(3D-TV)with shutter glasses.EEG was obtained from 10 volunteers when they were watching 3D film segments with di®erent negative disparities.The brain GF map shows that the depth information has a stronger in fluence on the frontal lobe than on the occipital lobe.For regression analysis,nonlinear curve fittings of GF to RJD in Fp1,F3,O2 and T5 channels were mainly performed when RJD ranged from 0 to 3.4,while linearfittings were performed in some special RJD ranges.It also confirms that RJD above 2.2 may lead to discomfort to human body.Finally,it suggests a suitable RJD range for people to watch from the objective method.The outcomes can be used as a guidance to decrease human discomforts induced by 3D production.展开更多
The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired.Here,the two-dimensional pillared MFI zeolite was modified by silicalit...The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired.Here,the two-dimensional pillared MFI zeolite was modified by silicalite-1,and its morphology and structure were systematically investigated by tuning the concentration of Si species during the secondary crystallization process.The MFI zeolites were characterized by X-ray diffraction,transmission electron microscopy,pyridine-infrared and N_(2) adsorption-desorption isotherms.The characterization results showed that the external Brønsted acid sites of surface passivated P-MFI-x samples have been successfully shielded.Interestingly,the P-MFI-23 showed long lifetime and high selectivity of para-xylene(about 35%)based on the cooperation between opened interlamellar structure and passivated silicalite-1 layer.It was found that the accumulated hard coke in the interior of MFI zeolites not only blocked the channels of zeolites but also covered the acidic sites,resulting in the deactivation of catalyst.Furthermore,the highest selectivity of para-xylene(about 48%)can be achieved for P-MFI-30 under harsh reaction condition,which also exhibited excellent regeneration property in the alkylation reaction between toluene and methanol.The strategy described in present research may open a window for the design of other advanced materials.展开更多
Green Perovskite Light-Emitting Diodes(PeLEDs)have attracted wide attention for full spectrum displays.However,the inferior film morphology and luminescence property of quasi-two-dimensional(quasi-2D)perovskite layers...Green Perovskite Light-Emitting Diodes(PeLEDs)have attracted wide attention for full spectrum displays.However,the inferior film morphology and luminescence property of quasi-two-dimensional(quasi-2D)perovskite layers limit the photoelectric property of the PeLEDs.In this paper,the effect of strontium(Sr)doped in quasi-2D perovskite layers is investigated to obtain a high-quality active layer.The morphologies and optical properties of Sr-doped quasi-2D perovskite films with different concentrations are studied.With the addition of strontium,more low-dimensional-layer perovskite phases(n D 2 and n D 3)appear in quasi-2D perovskite films,providing efficient intraband carrier funneling pathway and facilitating radiative recombination.The photoluminescence(PL)peak intensity of optimized Sr-doped quasi-2D perovskite layers increases 50%compared with the non-strontium counterpart.Moreover,green PeLEDs based on a Sr-doped quasi-2D perovskite layer reach a maximum luminance(Lmax)of 2943.77 cd/m^(2),which is three times of the control device.The electroluminescence(EL)peaks of Maximum External Quantum Efficiency(MEQE)and Lmax of Sr-doped PeLEDs exhibite a slight shift,indicating the excellent stability and performance of Sr-doped devices.The optimized device can continuously operate for 360 s at MEQE driving voltage,resulting in a half-lifetime of60 s,which is 3-fold greater than that of the control PeLEDs.展开更多
Two-dimensional electride Ca_(2)N has strong electron transfer ability and low work function,which is a potential candidate for hydrogen evolution reaction(HER)catalyst.In this work,based on density functional theory ...Two-dimensional electride Ca_(2)N has strong electron transfer ability and low work function,which is a potential candidate for hydrogen evolution reaction(HER)catalyst.In this work,based on density functional theory calculations,we adopt two strategies to improve the HER catalytic activity of Ca_(2)N monolayer:introducing Ca or N vacancy and doping transition metal atoms(TM,refers to Ti,V,Cr,Mn,Fe,Zr,Nb,Mo,Ru,Hf,Ta and W).Interestingly,the Gibbs free energyΔG_(H*)of Ca_(2)N monolayer after introducing N vacancy is reduced to-0.146 e V,showing good HER catalytic activity.It is highlighted that,the HER catalytic activity of Ca_(2)N monolayer can be further enhanced with TM doping,the Gibbs free energyΔG_(H*)of single Mo and double Mn doped Ca_(2)N are predicted to be 0.119 and 0.139 e V,respectively.The present results will provide good theoretical guidance for the HER catalysis applications of two-dimensional electride Ca_(2)N monolayer.展开更多
In recent years,Perovskite Light-Emitting Diodes(PeLEDs)have received considerable attention in academia.However,with the development of PeLEDs,commercial applications of full-color PeLED technology are largely limite...In recent years,Perovskite Light-Emitting Diodes(PeLEDs)have received considerable attention in academia.However,with the development of PeLEDs,commercial applications of full-color PeLED technology are largely limited by the progress of blue-emitting devices,due to the uncontrollably accurate composition,unstable properties,and low luminance.In this article,we add Cesium chloride(CsCl)to the quasi-two-dimensional(quasi-2D)perovskite precursor solution and achieve the relatively blue shifts of PeLED emission peak by introducing chloride ions for photoluminescence(PL)and electroluminescence(EL).We also found that the introduction of chlorine ions can make quasi-2D perovskite films thinner with smoother surface of 0.408 nm.It is interesting that the EL peaks and intensities of PeLED are adjustable under different driving voltages in high concentration chlorine-added perovskite devices,and different processes of photo-excited,photo-quenched,and photo-excited occur sequentially with the increasing driving voltage.Our work provides a path for demonstrating full-color screens in the future.展开更多
Regulable loading of Ni(OH)_(2) crystals by using three dimensionally ordered mesoporous carbon(3DOMC)as a support is achieved through a confined growth strategy accompanied by steam-assisted crystallization.Dual form...Regulable loading of Ni(OH)_(2) crystals by using three dimensionally ordered mesoporous carbon(3DOMC)as a support is achieved through a confined growth strategy accompanied by steam-assisted crystallization.Dual forms of high-crystalline nanosheet-like Ni(OH)_(2) severally distribute within mesopores or over the outer surface of 3DOMC particles depending on the loading amount(3%^(−1)5%)of Ni(OH)_(2).Benefitted from the highly hybrid combination and efficient electrolyte diffusion,the obtained Ni(OH)_(2)/carbon nanocomposites exhibit an excellent electrochemical performance,and the optimal sample of 6%_Ni(OH)_(2)/3DOMC with confined extrasmall Ni(OH)_(2) nanosheets as dominant shows the highest specific capacitance of 552.5F.g^(−1) at 1.0A⋅g^(−1),which is 330%higher than the contrast sample by using actived carbon as the support.Furthermore,the assembled hybrid supercapacitor by using 6%_Ni(OH)_(2)/3DOMC and 3DOMC as positive and negative electrodes displays an energy density of 11.7 Wh.kg^(−1) at 288.1 W.kg^(−1) and a superior charge/discharge stability.It is expected that the flexible component,well-defined structure,and superior electrochemical performance could promote a great application potential of Ni(OH)_(2)/3DOMC nanocomposites as supercapacitor electrodes and in other energy storage devices.展开更多
Titanosilicate pillared MFI zeolite nanosheets were successfully synthesized by infiltrating the mixed tetraethyl orthosilicate(TEOS)/tetrabutyl orthotitanate(TBOT)solvent into the gallery space between adjacent MFI z...Titanosilicate pillared MFI zeolite nanosheets were successfully synthesized by infiltrating the mixed tetraethyl orthosilicate(TEOS)/tetrabutyl orthotitanate(TBOT)solvent into the gallery space between adjacent MFI zeolite layers.The obtained zeolite catalysts were characterized using powder X-ray diffraction,N2 adsorption/desorption isotherms,scanning electron microscopy,transmission electron microscopy,ultraviolet-visible spectroscopy,X-ray photoelectron spectroscopy,and Fouriertransform infrared spectroscopy techniques.The H2〇2 oxidation of dibenzothiophene(DBT)was used to evaluate the catalytic performance of the obtained titanosilicate pillared MFI zeolites.The conversion of DBT and selectivity of dibenzothiophene sulfone(DBTS)were most affected by the textural properties of the zeolites.This was attributed to the DBT and DBTS molecules being larger than micropores of the MFI zeolites.The conversion of DBT and yield of DBTS could be systematically tailored by tuning the molar ratio of the TEOS/TBOT solvent.These results implied that a balance between the meso-and microporosity of zeolites and tetrahedrally coordinated Ti(IV)active sites of titanosilicate pillars can be achieved for the preparation of desired catalysts during the oxidation of bulk S compounds.展开更多
基金supported by the National Natural Science Foundation of China(22278090,21978055)Natural Science Foundation of Guangdong Province,China(2022A1515012088)the Science and Technology Planning Project of Guangdong Province,China(2022A0505030073,2022A0505030013).
文摘Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.
基金supported by NSFC(62273019,52072015,12332019,U20A20390)the 111 Project(B13003)。
文摘Dear Editor,This letter presents a biocompatible cross-shaped magnetic soft robot and investigates its deformation mode control strategy through COMSOL modeling and simulation.Magnetic soft robots offer novel avenues for precise treatment within intricate regions of the human body.
基金the Science and Technology Project of Maoming(China)(200203094555139)for financial support。
文摘The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously adjusting the p H instead of the traditional step-by-step method,which exhibited excellent performance in the catalytic oxidation of cyclopentene(CPE)to aldehydes or alcohols.The 93.69%CPE conversion and 97.15%total product selectivity(41.38%for glutaraldehyde(GA)and 55.77%for 1,2-cyclopentanediol(1,2-diol)were achieved by using H_(2)O_(2)as the oxidant and acetonitrile as the solvent.Through complementary characterization,it was found that the optimized di-lacunary silicotungstic polyoxometalate retained a complete Keggin structure,and exhibited better catalytic activity and stability than the mono-lacunary or saturated silicodecatungstate because it exposed more catalytic active centers.Furthermore,in situ FT-IR spectra was utilized to monitor the reaction process,revealing the formation of the active species W(O_(2))on the di-lacunary silicotungstic polyoxometalate and the intermediate epoxycyclopentane during the catalytic oxidation of cyclopentene.
基金supported by the National Natural Science Foundation of China (21978055, 22278090)Natural Science Foundation of Guangdong Province, China (2022A1515012088)+2 种基金the Science and Technology Planning Project of Guangdong Province, China (22A0505050073, 2022A0505030013)the Guangdong Provincial Key Laboratory of Plant Resources Biorefinery, China (2021GDKLPRB10)the "High-level Talents Program" of the Pearl River, China (2017GC010080)。
文摘Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.
基金the research grants provided by the National Natural Science Foundation of China (21576093)Guangdong Natural Science Funds for Distinguished Young Scholars (2016A030306031)+1 种基金Guangdong Natural Science Foundation (2014A030312007)Fundamental Research Funds for the Central Universities
文摘Adsorbent regeneration is critical for a continuous adsorption–regeneration process and often underestimated. In this work,the regeneration of bifunctional AgXO@SBA-15 for [O]-induced reactive adsorptive desulfurization of liquid fuel is reported and further investigated. The spent AgXO@SBA-15 was regenerated in various types of solvents followed by calcination and tested in multiple desulfurization–regeneration cycles. The effects of regenerate solvents were also compared systematically. The original and regenerated AgXO@SBA-15 was characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Nadsorption, X-ray photoelectron spectroscopy and atomic absorption spectrometry. The recovery of desulfurization capacity using various solvents follows the order of acetonitrile [ acetone [ ethanol [ methanol [ water. Owing to the complete reduction of silver species to Ag~0 and severe agglomeration of Ag~0, the bifunctional AgXO@SBA-15 demonstrating [ 85%(2.60 mg-S/g) of sulfur removal dramatically reduced to \ 46%(1.56 mg-S/g) after only 1 st-cycle regeneration. It is suggested that polar organic species strongly adsorbed(or residual) on the spent AgXO@SBA-15, in that case, after solvent wash may contribute to the accelerated decomposition of Ag~+ to Ag~0 in the following calcination step. The desulfurization capacity decreased rather mildly in the later regeneration runs. Cautious choice of regeneration conditions and strategies to rational design stabilized adsorbents is required to avert the adsorbent deactivation.
基金This project was supported by the Forestry Department Foundation of Guizhou Province of China(No.[2018]13)Natural Science Foundation of Guizhou Province(Nos.Qiankehe[2020]1Y125,[2019]1170)+2 种基金the Scientific and Technological Research Project of Guizhou Province(Nos.Qiankehe NY[2019]2325,[2019]2308)Education Department Foundation of Guizhou Province of China(Nos.QianJiaoHe KY Zi[2017]003,[2017]136)the Science and Technology Plan of Guizhou Province(No.Qiankehe Platform Talent[2017]5788).
文摘Lignin is an abundant renewable macromolecular material in nature,and degradation of lignin to improve its hydroxyl content is the key to its efficient use.Alkali lignin(AL)was treated with Brønsted acidic deep eutectic solvent(DES)based on choline chloride and p-toluenesulfonic acid at mild reaction temperature,the structure of the lignin before and after degradation,as well as the composition of small molecules of lignin were analyzed in order to investigate the chemical structure changes of lignin with DES treatment,and the degradation mechanism of lignin in this acidic DES was elucidated in this work.FTIR and NMR analyses demonstrated the selective cleavage of the lignin ether linkages in the degradation process,which was in line with the increased content of phenolic hydroxyl species.XPS revealed that the O/C atomic ratio of the regenerated lignin was lower than that of the AL sample,revealing that the lignin underwent decarbonylation during the DES treatment.Regenerated lignin with low molecular weight and narrow polydispersity index was obtained,and the average molecular weight(Mw)decreased from 17680 g/mol to 2792 g/mol(130°C,3 h)according to GPC analysis.The lignin-degraded products were mainly G-type phenolics and ketones,and small number of aldehydes were also generated,the possible degradation pathway of lignin in this acidic DES was proposed.
基金Supported by the Science and Technology Program of Guangzhou,China(201804010172)National Natural Science Foundation of China(21808040,21706031,21276052,21776049)Science and Technology Planning Project of Guangdong Province,China(2012A090300006)
文摘The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary combination of X-ray power diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), pyridine-IR spectroscopy and N2 adsorption–desorption isotherms. The analyses showed that the nitridation didn’t destroy the crystallinity and specific surface area of zeolites, and the acidity of zeolites can be tailored by tuning the time of nitridation, resulting in the different concentration ratios of Br?nsted-to-Lewis(B/L) acid sites. Moreover, the nitrided zeolites exhibited high selectivity to 2-benzyl-1,3,5-trimethylbenzene than parent silica pillared MFI zeolite nanosheets in benzylation of mesitylene with benzyl alcohol. A balance between Br?nsted acid sites and Lewis acid sites can inhibit the self-etherification of benzyl alcohol and enhance the selectivity of alkylated product. These experimental data implied that nitridation was an effective method to modulate the acidity of zeolites and the synergy between Br?nsted acid sites and Lewis acid sites was a decisive factor to determine the selectivity.
基金National Basic Research Program of China from MOST,2015CB910800 to W.C. and 2014CB910202 to J. LNational Science Foundation of China,31470900 and 31522021 to W.C. and 11672317 and 31222022 to J.L.
基金support from the National Science Foundation(NSF-CBET-1264599 and 1351384)support of the Maryland NanoCenter and its NispLab+1 种基金supported in part by the NSF as a MRSEC Shared Experimental Facilitythe China Scholarship Council (CSC) (No. 201306150076) for a fellowship to support his study at the University of Maryland
文摘Platinum and zinc containing LTA zeolite catalysts with tunable meso/microporosity were prepared by using ligand-metal precursors under hydrothermal condition. These materials were employed for oxidation of ethane to oxygenates using hydrogen peroxides as oxidant under mild reaction condition. The results showed that platinum and zinc loaded LTA zeolites were effective for the partial oxidation of ethane with hydrogen peroxide giving the desired C_2 oxygenates. Moreover, the C_1 oxygenates were also obtained through subsequent C–C bond scission pathways. The over oxidation of ethanol/methanol to acetic acid/formic acid could be inhibited through the introduction of mesoporosity in LTA zeolites. Our findings for oxidation of ethane suggested that the selectivity to the oxidation products such as alcohols and acids could be tailored by tuning the metal species within the LTA zeolites and porosity of catalysts, indicating that a balance between the meso/microporosity and metal species in LTA zeolites can be realized for desirable catalysis by one-pot synthesis of zeolites. In addition, the selectivity to oxygenates can also be tuned by control of the reaction conditions, i.e. concentration of hydrogen peroxide or reaction time.
基金This research was supported by the Nature Science Foundation of China(NSFC)(61171059&61075107)the twelfth"Five-Year Plan"National Key Technology R&D Program(2012BAI23B07)+1 种基金Funding of Jiangsu Innovation Program for Graduate Education (KYLX 0248)the Fundamental Research Funds for the Central Universities.
文摘The stereo vision results from the interaction between geometrical optics and visual psychology.Large depth will bring discomforts for the results of ghosting and flicker.The relevance of the ratio of jumping out depth(RJD)and electroencephalogram(EEG)gravity frequency(GF)was explored to re flect human health under di®erent three-dimensional(3D)depth information(mainly the negative disparity)displayed on a three-dimensional television(3D-TV)with shutter glasses.EEG was obtained from 10 volunteers when they were watching 3D film segments with di®erent negative disparities.The brain GF map shows that the depth information has a stronger in fluence on the frontal lobe than on the occipital lobe.For regression analysis,nonlinear curve fittings of GF to RJD in Fp1,F3,O2 and T5 channels were mainly performed when RJD ranged from 0 to 3.4,while linearfittings were performed in some special RJD ranges.It also confirms that RJD above 2.2 may lead to discomfort to human body.Finally,it suggests a suitable RJD range for people to watch from the objective method.The outcomes can be used as a guidance to decrease human discomforts induced by 3D production.
基金supported by the National Natural Science Foundation of China(Grant Nos.22278090,21978055)the Natural Science Foundation of Guangdong Province(Grant No.2022A1515012088)the Science and Technology Program of Guangdong Province(Grant No.2022A0505050073).
文摘The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired.Here,the two-dimensional pillared MFI zeolite was modified by silicalite-1,and its morphology and structure were systematically investigated by tuning the concentration of Si species during the secondary crystallization process.The MFI zeolites were characterized by X-ray diffraction,transmission electron microscopy,pyridine-infrared and N_(2) adsorption-desorption isotherms.The characterization results showed that the external Brønsted acid sites of surface passivated P-MFI-x samples have been successfully shielded.Interestingly,the P-MFI-23 showed long lifetime and high selectivity of para-xylene(about 35%)based on the cooperation between opened interlamellar structure and passivated silicalite-1 layer.It was found that the accumulated hard coke in the interior of MFI zeolites not only blocked the channels of zeolites but also covered the acidic sites,resulting in the deactivation of catalyst.Furthermore,the highest selectivity of para-xylene(about 48%)can be achieved for P-MFI-30 under harsh reaction condition,which also exhibited excellent regeneration property in the alkylation reaction between toluene and methanol.The strategy described in present research may open a window for the design of other advanced materials.
基金supported by the National Natural Science Foundation of China (Nos.61875186,61975196,and 61674140)。
文摘Green Perovskite Light-Emitting Diodes(PeLEDs)have attracted wide attention for full spectrum displays.However,the inferior film morphology and luminescence property of quasi-two-dimensional(quasi-2D)perovskite layers limit the photoelectric property of the PeLEDs.In this paper,the effect of strontium(Sr)doped in quasi-2D perovskite layers is investigated to obtain a high-quality active layer.The morphologies and optical properties of Sr-doped quasi-2D perovskite films with different concentrations are studied.With the addition of strontium,more low-dimensional-layer perovskite phases(n D 2 and n D 3)appear in quasi-2D perovskite films,providing efficient intraband carrier funneling pathway and facilitating radiative recombination.The photoluminescence(PL)peak intensity of optimized Sr-doped quasi-2D perovskite layers increases 50%compared with the non-strontium counterpart.Moreover,green PeLEDs based on a Sr-doped quasi-2D perovskite layer reach a maximum luminance(Lmax)of 2943.77 cd/m^(2),which is three times of the control device.The electroluminescence(EL)peaks of Maximum External Quantum Efficiency(MEQE)and Lmax of Sr-doped PeLEDs exhibite a slight shift,indicating the excellent stability and performance of Sr-doped devices.The optimized device can continuously operate for 360 s at MEQE driving voltage,resulting in a half-lifetime of60 s,which is 3-fold greater than that of the control PeLEDs.
基金supported by the National Natural Science Foundation of China(No.21973012)the Natural Science Foundation of Fujian Province(Nos.2020J01474,2021J06011 and 2020J01351)the"Qishan Scholar"Scientific Research Project of Fuzhou University。
文摘Two-dimensional electride Ca_(2)N has strong electron transfer ability and low work function,which is a potential candidate for hydrogen evolution reaction(HER)catalyst.In this work,based on density functional theory calculations,we adopt two strategies to improve the HER catalytic activity of Ca_(2)N monolayer:introducing Ca or N vacancy and doping transition metal atoms(TM,refers to Ti,V,Cr,Mn,Fe,Zr,Nb,Mo,Ru,Hf,Ta and W).Interestingly,the Gibbs free energyΔG_(H*)of Ca_(2)N monolayer after introducing N vacancy is reduced to-0.146 e V,showing good HER catalytic activity.It is highlighted that,the HER catalytic activity of Ca_(2)N monolayer can be further enhanced with TM doping,the Gibbs free energyΔG_(H*)of single Mo and double Mn doped Ca_(2)N are predicted to be 0.119 and 0.139 e V,respectively.The present results will provide good theoretical guidance for the HER catalysis applications of two-dimensional electride Ca_(2)N monolayer.
基金supported by the National Key Research and Development Program of China(No.2018YFB2200103)the National Natural Science Foundation of China(Nos.61875186 and 61975196)+2 种基金the Project of the Natural Science Foundation of Beijing(No.Z160002)the Key Research Projects of Beijing Information Science and Technology University(BISTU)(Nos.2019-22,2019-23,2019-27)the Beijing Key Laboratory for Sensors of BISTU(No.2019CGKF007)。
文摘In recent years,Perovskite Light-Emitting Diodes(PeLEDs)have received considerable attention in academia.However,with the development of PeLEDs,commercial applications of full-color PeLED technology are largely limited by the progress of blue-emitting devices,due to the uncontrollably accurate composition,unstable properties,and low luminance.In this article,we add Cesium chloride(CsCl)to the quasi-two-dimensional(quasi-2D)perovskite precursor solution and achieve the relatively blue shifts of PeLED emission peak by introducing chloride ions for photoluminescence(PL)and electroluminescence(EL).We also found that the introduction of chlorine ions can make quasi-2D perovskite films thinner with smoother surface of 0.408 nm.It is interesting that the EL peaks and intensities of PeLED are adjustable under different driving voltages in high concentration chlorine-added perovskite devices,and different processes of photo-excited,photo-quenched,and photo-excited occur sequentially with the increasing driving voltage.Our work provides a path for demonstrating full-color screens in the future.
基金the National Natural Science Foundation of China(Nos.21978238,21878248,and 21978055)Natural Science Foundation of Shaanxi Provincial Department of Education(No.21JY041).
文摘Regulable loading of Ni(OH)_(2) crystals by using three dimensionally ordered mesoporous carbon(3DOMC)as a support is achieved through a confined growth strategy accompanied by steam-assisted crystallization.Dual forms of high-crystalline nanosheet-like Ni(OH)_(2) severally distribute within mesopores or over the outer surface of 3DOMC particles depending on the loading amount(3%^(−1)5%)of Ni(OH)_(2).Benefitted from the highly hybrid combination and efficient electrolyte diffusion,the obtained Ni(OH)_(2)/carbon nanocomposites exhibit an excellent electrochemical performance,and the optimal sample of 6%_Ni(OH)_(2)/3DOMC with confined extrasmall Ni(OH)_(2) nanosheets as dominant shows the highest specific capacitance of 552.5F.g^(−1) at 1.0A⋅g^(−1),which is 330%higher than the contrast sample by using actived carbon as the support.Furthermore,the assembled hybrid supercapacitor by using 6%_Ni(OH)_(2)/3DOMC and 3DOMC as positive and negative electrodes displays an energy density of 11.7 Wh.kg^(−1) at 288.1 W.kg^(−1) and a superior charge/discharge stability.It is expected that the flexible component,well-defined structure,and superior electrochemical performance could promote a great application potential of Ni(OH)_(2)/3DOMC nanocomposites as supercapacitor electrodes and in other energy storage devices.
基金This work was funded by the National Natural Science Foundation of China(Grant Nos.21808040,51476176,and 21776049)The support of the Science and Technology Program of Guangzhou,China(Grant No.201804010172)is also gratefully acknowledged.
文摘Titanosilicate pillared MFI zeolite nanosheets were successfully synthesized by infiltrating the mixed tetraethyl orthosilicate(TEOS)/tetrabutyl orthotitanate(TBOT)solvent into the gallery space between adjacent MFI zeolite layers.The obtained zeolite catalysts were characterized using powder X-ray diffraction,N2 adsorption/desorption isotherms,scanning electron microscopy,transmission electron microscopy,ultraviolet-visible spectroscopy,X-ray photoelectron spectroscopy,and Fouriertransform infrared spectroscopy techniques.The H2〇2 oxidation of dibenzothiophene(DBT)was used to evaluate the catalytic performance of the obtained titanosilicate pillared MFI zeolites.The conversion of DBT and selectivity of dibenzothiophene sulfone(DBTS)were most affected by the textural properties of the zeolites.This was attributed to the DBT and DBTS molecules being larger than micropores of the MFI zeolites.The conversion of DBT and yield of DBTS could be systematically tailored by tuning the molar ratio of the TEOS/TBOT solvent.These results implied that a balance between the meso-and microporosity of zeolites and tetrahedrally coordinated Ti(IV)active sites of titanosilicate pillars can be achieved for the preparation of desired catalysts during the oxidation of bulk S compounds.