A facile template-free in situ self-activation approach for the multiple active components synergistically driven porous carbon was presented via a feasible annealing process.The biomass-derived carbon without additio...A facile template-free in situ self-activation approach for the multiple active components synergistically driven porous carbon was presented via a feasible annealing process.The biomass-derived carbon without additional activation reagents was fabricated using K-rich pomelo peel(PP)as the carbon source,which possesses a high electric conductivity where abundant functional hetero-metal atoms are doped into the carbon framework that playing the role of catalytic graphitization.The K^+that exists within the biomass can induce self-activation during pyrolysis apart from the activating gases during the pyrolysis process.The resulting electrocatalyst of PP-850(PP was pyrolyzed at 850°C in an N_2atmosphere)with abundant heteroatoms possesses a higher power conversion efficiency(PCE)of 7.81%as the counter electrode(CE)of dye-sensitized solar cells(DSCs)compared with the CEs calcinated at other temperatures and a similar PCE with Pt counterpart(8.24%)based on the liquid I_3^-/I^-electrolyte.The better electrocatalytic performance is attributed to the synergistic effect between self-activation and the co-doping of nitrogen,sulfur and phosphorus all together in a carbon matrix.Due to the feasibility of large-scale production,rich heteroatom doping,the PP-derived carbon,which simplifies the procedure and decreases the cost,has a potential application for an alternative electrocatalyst for high-performance photovoltaic devices.展开更多
One of the major challenges associated with fuel cells is the design of highly efficient electrocatalysts to reduce the high overpotential of the oxygen reduction reaction(ORR). Here we report Polyaniline(PANI)based m...One of the major challenges associated with fuel cells is the design of highly efficient electrocatalysts to reduce the high overpotential of the oxygen reduction reaction(ORR). Here we report Polyaniline(PANI)based micro/nanomaterials with or without transition metals, prepared by the emulsion polymerization and subsequent heat treatment. PANI microspheres with the diameter of about 0.7 μm have been prepared in basic(NH3solution) condition, using two different types of surfactant(CTAB, SDS) as the stabilizer, ammonium persulphate(APS) as oxidant with aniline/surfactants molar ratio at 1/1 under the hydrothermal treatment. PANI nanorods, Fe–PANI, and Fe–Co–PANI have been synthesized in acidic(HCl)medium with aniline/surfactants molar ratio at 1/2 and polymerization carried out without stirring for24 h. Products mainly Fe–Co–PANI have shown high current density with increasing sweep rate and excellent specific capacitance 1753 F/g at the scan rate of 1 m V/s. Additionally, it has shown high thermal stability by thermogravimetric analysis(TGA). Fe–PANI has been investigated for excellent performance toward ORR with four electron selectivity in the basic electrolyte. The PANI-based catalysts from emulsion polymerization demonstrate that the method is valuable for making non-precious metal heterogeneous electrocatalysts for ORR or energy storage and conversion technology.展开更多
The parasitic polysulfides shuttle effect greatly hinders the practical application of lithium sulfur batteries,and this issue can be addressed by promoting polysulfides conversion with catalytic materials such as Mo ...The parasitic polysulfides shuttle effect greatly hinders the practical application of lithium sulfur batteries,and this issue can be addressed by promoting polysulfides conversion with catalytic materials such as Mo S_(2).However,the catalytic activity of Mo S_(2)mainly relies on edge sites,but is limited by inert basal planes.We herein report a novel,facile,ethylene glycol enabled competing reduction strategy to dope Mo S_(2)homogeneously with oxygen atoms so that its inert basal planes can be unlocked.Ethylene glycol works as a reducing agent and competes with thiourea to react with ammonium molybdate,leading to insufficient sulfuration of Mo,and consequent formation of O-Mo S_(2).Our theoretical and experimental investigations indicate that the homogeneously distributed O dopants can create abundant adsorption/-catalytic sites in the Mo S_(2)basal planes,enlarge the inter-plane distance to promote ion transport,and thus enhance the catalytic conversion of polysulfides.The oxygen doped Mo S_(2)(O-Mo S_(2))is supported on carbon nanosheets(CNS)and the composite(O-Mo S_(2)/CNS)is employed to modify the separator of Li-S battery.It gives the battery an initial discharge capacity of 1537 m Ah g-1at 0.2 C,and the battery retains a discharge capacity of 545 m Ah g-1after ultra-long 2000 cycles at 1 C,corresponding to a very small cyclic decay rate of 0.0237%.Even under a raising sulfur loading of 8.2 mg cm^(-2),the Li-S battery also delivers a high discharge capacity(554 m Ah g^(-1))with outstanding cycle stability(84.6%capacity retention)after 100 cycles at 0.5 C.Our work provides a novel,facile approach to fabricate highly catalytically active oxygen-doped Mo S_(2)for advanced Li-S batteries.展开更多
For some specific catalytic reaction, how to construct active sites on two dimensional materials is of great scientific significance. Dye-sensitized solar cells(DSCs) can be viewed as one representative photovoltaics ...For some specific catalytic reaction, how to construct active sites on two dimensional materials is of great scientific significance. Dye-sensitized solar cells(DSCs) can be viewed as one representative photovoltaics because in which liquid electrolyte with triiodide/iodide(I_3^-/I^-) as redox couples are involved. In this study, amino-functionalized graphene(AFG) has been designed according to theoretically analyzing iodine reduction reaction(IRR) processes and rationally screening the volcanic plot. Then, such AFG has been successfully synthesized by a simple hydrothermal method and shows high electrocatalytic activity towards IRR when serving as counter electrode in DSCs. Finally, a high conversion efficiency of 7.39% by AFG-based DSCs was obtained, which is close to that using Pt as counter electrode.展开更多
Currently,pyrolysis as the most widely used method still has some key issues not well resolved for synthesis of carbon-supported single-atom catalysts(C-SACs),e.g.,the sintering of metal atoms at high temperature as w...Currently,pyrolysis as the most widely used method still has some key issues not well resolved for synthesis of carbon-supported single-atom catalysts(C-SACs),e.g.,the sintering of metal atoms at high temperature as well as the high cost and complicated preparations of precursors.In this report,molten salts are demonstrated to be marvellous medium for preparation of C-SACs by pyrolysis of small molecular precursors(ionic liquid).The ultrastrong polarity on one hand establishes robust interaction with precursor and enables better carbonization,resulting in largely enhanced yield.On the other hand,the aggregation of metal atoms is effectively refrained while no nanoparticle or cluster is formed.By this strategy,a C-SAC with atomically dispersed Fe-N_(4) sites and a high specific area over 2000 m^(2) g^(-1) is obtained,which illustrates high ORR activity in both acid and alkaline media.Moreover,this SAC exhibits superior methanol tolerance and stability after acid soaking at 85℃ for 48 h.It is believed that the molten-salts-assisted pyrolysis can be developed into a routine strategy as it not only can largely simply the synthesis of C-SACs,but also can be extended to prepare other types of SACs.展开更多
Recently,an effective exciton diffusion length L exceeding 100μm has been reported for organic–inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons;however,the origin ...Recently,an effective exciton diffusion length L exceeding 100μm has been reported for organic–inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons;however,the origin of ultra-long L is still unclear in nature.In some photoelectric materials,reverse intersystem crossing(RISC)from the triplet to the singlet state can enhance the quantum yield of photoluminescence greatly.In this study,our theoretical investigation indicated that the energy difference E_(st )between the singlet state and the triplet state of CH_3NH_3PbI_3was less than 0.1 e V,which represents one crucial prerequisite for the occurrence of RISC.Meanwhile,the experimental results showed that the photoluminescence lifetime increased with the increasing temperature,a typical feature of RISC.Based on this study,we put forward the hypothesis that the ultra-long lifetime of excitons in organic–inorganic halide perovskite might be caused by the RISC process.This may provide a new insight into the important photophysical properties of such novel photovoltaic materials.展开更多
Converting CO2 to carbon-containing fuels is an effective approach to relieving energy shortages.Carbon quantum dots(CQDs) have shown distinct properties and attracted tremendous interest in CO2 reduction.Herein,we re...Converting CO2 to carbon-containing fuels is an effective approach to relieving energy shortages.Carbon quantum dots(CQDs) have shown distinct properties and attracted tremendous interest in CO2 reduction.Herein,we report a joint experimental-computational mechanistic study of photoreduction CO2 to CO on the model catalyst 9-hydroxyphenal-1-one(HPHN) CQDs with known structure.Our theoretical calculations reveal that the rate-determining step is COOH·formation,which is closely related to the proton and electron transfer induced by hydrogen bonding in the excited state.According to the calculated volcano plot,the solution we proposed is addition Zn^(2+) ions.The active center changed from the hydroxyl oxygen atom to the Zn atom and the barrier of the COOH·formation step is noticeably decreased when Zn^(2+) ions are added.It is further confirmed by the experimental data that the activity of CO2 reduction increases 2.9 times when Zn^(2+) ions are added.展开更多
In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process i...In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process is established and the necessary assumptions are made.Then,the establishment process of the multi-physical field model of the melt pool is introduced in detail.It is concluded that the simulation model results are highly consistent with the online measurement experiment results in terms of melt pool profile,space temperature gradient,and time temperature gradient.Meanwhile,some parameters,such as the 3D morphology and surface fluid field of the melt pool,which are not obtained in the online measurement experiment,are analyzed.Finally,the influence of changing the scanning speed on the profile,peak temperature,and temperature gradient of the single-line melt pool is also analyzed,and the following conclusions are obtained:With the increase in scanning speed,the profile of the melt pool gradually becomes slender;The relationship between peak temperature and scanning speed is approximately linear in a certain speed range;The space temperature gradient at the tail of the melt pool under different scanning speeds hardly changes with the scanning speed,and the time temperature gradient at the tail of the melt pool is in direct proportion to the scanning speed.展开更多
In the article titled“The Tianwen-1 Guidance,Navigation,and Control for Mars Entry,Descent,and Landing”[1],there was an error in Figure 9(b).On the y-axis,the data read q1,q2,and q1.It should have read q1,q2,and q3....In the article titled“The Tianwen-1 Guidance,Navigation,and Control for Mars Entry,Descent,and Landing”[1],there was an error in Figure 9(b).On the y-axis,the data read q1,q2,and q1.It should have read q1,q2,and q3.This is updated as shown in Figure 1 below.展开更多
Tianwen-1,the first mission of China’s planetary exploration program,accomplished its goals of orbiting,landing,and roving on the Mars.The entry,descent,and landing(EDL)phase directly determines the success of the en...Tianwen-1,the first mission of China’s planetary exploration program,accomplished its goals of orbiting,landing,and roving on the Mars.The entry,descent,and landing(EDL)phase directly determines the success of the entire mission,of which the guidance,navigation,and control(GNC)system is crucial.This paper outlines the Tianwen-1 EDL GNC system design by introducing the GNC requirements followed by presenting the GNC system architecture and algorithms to meet such requirements.The actual flight results for the whole EDL phase are also provided in this paper.展开更多
Impeding high temperature sintering is challengeable for synthesis of carbon-supported single-atom catalysts (C-SACs), which requires high-cost precursor and strictly-controlled procedures. Herein, by virtue of the ul...Impeding high temperature sintering is challengeable for synthesis of carbon-supported single-atom catalysts (C-SACs), which requires high-cost precursor and strictly-controlled procedures. Herein, by virtue of the ultrastrong polarity of salt melts, sintering of metal atoms is effectively suppressed. Meanwhile, doping with inorganic sulfur anions not only produces sufficient anchoring sites to achieve high loading of atomically dispersed Co up to 13.85 wt.%, but also enables their electronic and geometric structures to be well tuned. When served as a cathode catalyst in dye-sensitized solar cells, the C-SAC with Co-N4-S2 moieties exhibits high activity towards the iodide reduction reaction (IRR), achieving a higher power conversion efficiency than that of conventional Pt counterpart. Density function theory (DFT) calculations revealed that the superior IRR activity was ascribed to the unique structure of Co-N4-S2 moieties with lower reaction barriers and moderate binding energy of iodine on the Co center, which was beneficial to I2 dissociation.展开更多
Sulfamethoxypyridazine(SMP) is one of the commonly used sulfonamide antibiotics(SAs).SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic ...Sulfamethoxypyridazine(SMP) is one of the commonly used sulfonamide antibiotics(SAs).SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic environmental organic pollutants.In this work,SMP was selected as a representative of SAs.We studied the mechanisms of triplet-sensitized photodegradation of SMP and the influence of selected dissolved inorganic matter,i.e.,anions(Br^-,Cl^-,and NO^-_3) and cations ions(Ca^(2+),Mg^(2+),and Zn^(2+)) on SMP photodegradation mechanism by quantum chemical methods.In addition,the degradation mechanisms of SMP by hydroxyl radical(OH·) were also investigated.The creation of SO_2 extrusion product was accessed with two different energy pathways(pathway-1 and pathway-2) by following two steps(step-I and step-II) in the tripletsensitized photodegradation of SMP.Due to low activation energy,the pathway-1 was considered as the main pathway to obtain SO_2 extrusion product.Step-II of pathway-1 was measured to be the rate-limiting step(RLS) of SMP photodegradation mechanism and the effect of the selected anions and cations was estimated for this step.All selected anions and cations promoted photodegradation of SMP by dropping the activation energy of pathway-1.The estimated low activation energies of different degradation pathways of SMP with OH·radical indicate that OH·radical is a very powerful oxidizing agent for SMP degradation via attack through benzene derivative and pyridazine derivative ring.展开更多
The stability of anion exchange membranes(AEMs) is an important feature of alkaline exchange membrane fuel cells(AEMFCs), which has been extensively studied. However it remains a real challenge due to the harsh workin...The stability of anion exchange membranes(AEMs) is an important feature of alkaline exchange membrane fuel cells(AEMFCs), which has been extensively studied. However it remains a real challenge due to the harsh working condition. Herein, we developed a novel type of polysulfone-based AEMs with three modified 1,2-dimethylbenzimidazoliums containing different substitutes at C4-and C7-position. The results showed that the introduction of the substitutes could obviously improve the dimensional and alkaline stabilities of the corresponding membranes. The swelling ratios of resultant AEMs were all lower than 10% after water immersion. The membrane with 4,7-dimethoxy-1,2-dimethylbenzimidazolium group exhibited the highest alkaline stability. Only 9.2% loss of hydroxide conductivity was observed after treating the membrane in 1 mol·L^(-1) KOH solution at 80 °C for 336 h. Furthermore, the density functional theory(DFT) study on the three functional group models showed that the substitutes at C4-and C7-position affected the lowest unoccupied molecular orbital(LUMO) energies of the different 1,2-dimethylbenzimidazolium groups.展开更多
All-inorganic cesium lead halide perovskites(CsPbX_3, X = Cl^-,Br^-, I^-) could provide comparable optoelectronic properties as a promising class of materials for photovoltaic cell(PV), photodetector and light-emittin...All-inorganic cesium lead halide perovskites(CsPbX_3, X = Cl^-,Br^-, I^-) could provide comparable optoelectronic properties as a promising class of materials for photovoltaic cell(PV), photodetector and light-emitting diode(LED) with enhanced thermal and moisture stabilities compared to organicinorganic lead halide species. However, fabrication of CsPbI_3 perovskite via facile solution process has been difficult due to instability of CsPbI_3 in the perovskite cubic phase in ambient air. Herein, we report the synthesis of CsPbI_3 perovskite microcrystals by low-temperature, catalyst-free, solution-phase method. By applying the time-resolve spectroscopic technique, we determine the carrier diffusion coefficient of 0.6–1.2 cm^2/s, the intrinsic carrier lifetimes of 200–1300 ns and diffusion length of 4–10μm in different individual CsPbI_3 perovskite microcrystals. Our results suggest the CsPbI_3 perovskite microcrystals synthesized by solution process exhibit high quality feature and are suitable for applications in optoelectronic devices.展开更多
基金financial assistance from the National Natural Science Foundation of China (Grant nos. 51402036 and 51773025)the International Science & Technology Cooperation Program of China (Grant no. 2013DFA51000)
文摘A facile template-free in situ self-activation approach for the multiple active components synergistically driven porous carbon was presented via a feasible annealing process.The biomass-derived carbon without additional activation reagents was fabricated using K-rich pomelo peel(PP)as the carbon source,which possesses a high electric conductivity where abundant functional hetero-metal atoms are doped into the carbon framework that playing the role of catalytic graphitization.The K^+that exists within the biomass can induce self-activation during pyrolysis apart from the activating gases during the pyrolysis process.The resulting electrocatalyst of PP-850(PP was pyrolyzed at 850°C in an N_2atmosphere)with abundant heteroatoms possesses a higher power conversion efficiency(PCE)of 7.81%as the counter electrode(CE)of dye-sensitized solar cells(DSCs)compared with the CEs calcinated at other temperatures and a similar PCE with Pt counterpart(8.24%)based on the liquid I_3^-/I^-electrolyte.The better electrocatalytic performance is attributed to the synergistic effect between self-activation and the co-doping of nitrogen,sulfur and phosphorus all together in a carbon matrix.Due to the feasibility of large-scale production,rich heteroatom doping,the PP-derived carbon,which simplifies the procedure and decreases the cost,has a potential application for an alternative electrocatalyst for high-performance photovoltaic devices.
基金support by the National Natural Science Foundation of China(Grant no.21373042)
文摘One of the major challenges associated with fuel cells is the design of highly efficient electrocatalysts to reduce the high overpotential of the oxygen reduction reaction(ORR). Here we report Polyaniline(PANI)based micro/nanomaterials with or without transition metals, prepared by the emulsion polymerization and subsequent heat treatment. PANI microspheres with the diameter of about 0.7 μm have been prepared in basic(NH3solution) condition, using two different types of surfactant(CTAB, SDS) as the stabilizer, ammonium persulphate(APS) as oxidant with aniline/surfactants molar ratio at 1/1 under the hydrothermal treatment. PANI nanorods, Fe–PANI, and Fe–Co–PANI have been synthesized in acidic(HCl)medium with aniline/surfactants molar ratio at 1/2 and polymerization carried out without stirring for24 h. Products mainly Fe–Co–PANI have shown high current density with increasing sweep rate and excellent specific capacitance 1753 F/g at the scan rate of 1 m V/s. Additionally, it has shown high thermal stability by thermogravimetric analysis(TGA). Fe–PANI has been investigated for excellent performance toward ORR with four electron selectivity in the basic electrolyte. The PANI-based catalysts from emulsion polymerization demonstrate that the method is valuable for making non-precious metal heterogeneous electrocatalysts for ORR or energy storage and conversion technology.
基金financial support from the fund for Creative Research Groups of the National Natural Science Foundation of China(22021005)the Science and Technology Innovation Fund of Dalian(2018J12GX052)+3 种基金the National Natural Science Foundation of China(21776042,22108027)the Fundamental Research Funds for the Central Universities of China(DUT19ZD214)the Shenzhen Science and Technology Program(201908163000519)the GDSTC-Key R&D Project(GDSTC No.2019B090908001)。
文摘The parasitic polysulfides shuttle effect greatly hinders the practical application of lithium sulfur batteries,and this issue can be addressed by promoting polysulfides conversion with catalytic materials such as Mo S_(2).However,the catalytic activity of Mo S_(2)mainly relies on edge sites,but is limited by inert basal planes.We herein report a novel,facile,ethylene glycol enabled competing reduction strategy to dope Mo S_(2)homogeneously with oxygen atoms so that its inert basal planes can be unlocked.Ethylene glycol works as a reducing agent and competes with thiourea to react with ammonium molybdate,leading to insufficient sulfuration of Mo,and consequent formation of O-Mo S_(2).Our theoretical and experimental investigations indicate that the homogeneously distributed O dopants can create abundant adsorption/-catalytic sites in the Mo S_(2)basal planes,enlarge the inter-plane distance to promote ion transport,and thus enhance the catalytic conversion of polysulfides.The oxygen doped Mo S_(2)(O-Mo S_(2))is supported on carbon nanosheets(CNS)and the composite(O-Mo S_(2)/CNS)is employed to modify the separator of Li-S battery.It gives the battery an initial discharge capacity of 1537 m Ah g-1at 0.2 C,and the battery retains a discharge capacity of 545 m Ah g-1after ultra-long 2000 cycles at 1 C,corresponding to a very small cyclic decay rate of 0.0237%.Even under a raising sulfur loading of 8.2 mg cm^(-2),the Li-S battery also delivers a high discharge capacity(554 m Ah g^(-1))with outstanding cycle stability(84.6%capacity retention)after 100 cycles at 0.5 C.Our work provides a novel,facile approach to fabricate highly catalytically active oxygen-doped Mo S_(2)for advanced Li-S batteries.
基金Financial support provided by the National Natural Science Foundation of China (Grant No. 51402036, 21373042)International Science & Technology Cooperation Program of China (Grant No. 2013DFA51000)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. DUT15YQ109)supported by the State Key Laboratory of Fine Chemicals of China
文摘For some specific catalytic reaction, how to construct active sites on two dimensional materials is of great scientific significance. Dye-sensitized solar cells(DSCs) can be viewed as one representative photovoltaics because in which liquid electrolyte with triiodide/iodide(I_3^-/I^-) as redox couples are involved. In this study, amino-functionalized graphene(AFG) has been designed according to theoretically analyzing iodine reduction reaction(IRR) processes and rationally screening the volcanic plot. Then, such AFG has been successfully synthesized by a simple hydrothermal method and shows high electrocatalytic activity towards IRR when serving as counter electrode in DSCs. Finally, a high conversion efficiency of 7.39% by AFG-based DSCs was obtained, which is close to that using Pt as counter electrode.
基金supported by the National Natural Science Foundation of China(21406031,21476044,U1663223)the Changjiang Scholars Program(T2012049)+3 种基金the State Key Laboratory of Fine Chemicals(KF1507)Dalian High-Level Talent Support Program(2015R056)Education Department of the Liaoning Province of China(LT2015007)Fundamental Research Funds for the Central Universities(DUT16TD19)~~
基金financially supported by the National Natural Science Foundation of China(Grant No.51773025)the Natural Science Foundation of Liaoning Province(Materials Joint Foundation,Grant No.20180510027)Dalian science and technology innovation fund(Grant No.019J12GX032)。
文摘Currently,pyrolysis as the most widely used method still has some key issues not well resolved for synthesis of carbon-supported single-atom catalysts(C-SACs),e.g.,the sintering of metal atoms at high temperature as well as the high cost and complicated preparations of precursors.In this report,molten salts are demonstrated to be marvellous medium for preparation of C-SACs by pyrolysis of small molecular precursors(ionic liquid).The ultrastrong polarity on one hand establishes robust interaction with precursor and enables better carbonization,resulting in largely enhanced yield.On the other hand,the aggregation of metal atoms is effectively refrained while no nanoparticle or cluster is formed.By this strategy,a C-SAC with atomically dispersed Fe-N_(4) sites and a high specific area over 2000 m^(2) g^(-1) is obtained,which illustrates high ORR activity in both acid and alkaline media.Moreover,this SAC exhibits superior methanol tolerance and stability after acid soaking at 85℃ for 48 h.It is believed that the molten-salts-assisted pyrolysis can be developed into a routine strategy as it not only can largely simply the synthesis of C-SACs,but also can be extended to prepare other types of SACs.
基金The financial supports of the National Natural Science Foundation of China (grant nos. 21373042, 21677029 and 51402036)the Fundamental Research Funds for the Central Universities (grant no. DUT15YQ109)
文摘Recently,an effective exciton diffusion length L exceeding 100μm has been reported for organic–inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons;however,the origin of ultra-long L is still unclear in nature.In some photoelectric materials,reverse intersystem crossing(RISC)from the triplet to the singlet state can enhance the quantum yield of photoluminescence greatly.In this study,our theoretical investigation indicated that the energy difference E_(st )between the singlet state and the triplet state of CH_3NH_3PbI_3was less than 0.1 e V,which represents one crucial prerequisite for the occurrence of RISC.Meanwhile,the experimental results showed that the photoluminescence lifetime increased with the increasing temperature,a typical feature of RISC.Based on this study,we put forward the hypothesis that the ultra-long lifetime of excitons in organic–inorganic halide perovskite might be caused by the RISC process.This may provide a new insight into the important photophysical properties of such novel photovoltaic materials.
基金supported by the National Natural Science Foundation of China (Grant Nos. 21677029, 21606040)the Fundamental Research Funds for the Central Universities (DUT18LK26)。
文摘Converting CO2 to carbon-containing fuels is an effective approach to relieving energy shortages.Carbon quantum dots(CQDs) have shown distinct properties and attracted tremendous interest in CO2 reduction.Herein,we report a joint experimental-computational mechanistic study of photoreduction CO2 to CO on the model catalyst 9-hydroxyphenal-1-one(HPHN) CQDs with known structure.Our theoretical calculations reveal that the rate-determining step is COOH·formation,which is closely related to the proton and electron transfer induced by hydrogen bonding in the excited state.According to the calculated volcano plot,the solution we proposed is addition Zn^(2+) ions.The active center changed from the hydroxyl oxygen atom to the Zn atom and the barrier of the COOH·formation step is noticeably decreased when Zn^(2+) ions are added.It is further confirmed by the experimental data that the activity of CO2 reduction increases 2.9 times when Zn^(2+) ions are added.
基金This work was financially supported by the National Key R&D Program of China(Grant No.2017YFB1103900)National Natural Science Foundation of China(Grant No.11972084)+1 种基金National Science and Technology Major Project(2017-VI-0003-0073)Beijing National Science Foundation(1192014).
文摘In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process is established and the necessary assumptions are made.Then,the establishment process of the multi-physical field model of the melt pool is introduced in detail.It is concluded that the simulation model results are highly consistent with the online measurement experiment results in terms of melt pool profile,space temperature gradient,and time temperature gradient.Meanwhile,some parameters,such as the 3D morphology and surface fluid field of the melt pool,which are not obtained in the online measurement experiment,are analyzed.Finally,the influence of changing the scanning speed on the profile,peak temperature,and temperature gradient of the single-line melt pool is also analyzed,and the following conclusions are obtained:With the increase in scanning speed,the profile of the melt pool gradually becomes slender;The relationship between peak temperature and scanning speed is approximately linear in a certain speed range;The space temperature gradient at the tail of the melt pool under different scanning speeds hardly changes with the scanning speed,and the time temperature gradient at the tail of the melt pool is in direct proportion to the scanning speed.
文摘In the article titled“The Tianwen-1 Guidance,Navigation,and Control for Mars Entry,Descent,and Landing”[1],there was an error in Figure 9(b).On the y-axis,the data read q1,q2,and q1.It should have read q1,q2,and q3.This is updated as shown in Figure 1 below.
基金This work is supported by the Chinese National Space Administration(CNSA).Parts of the work are supported by the National Natural Science Foundation of China(Grant No.61503023,No.61673057,No.61803028,and No.61903032).
文摘Tianwen-1,the first mission of China’s planetary exploration program,accomplished its goals of orbiting,landing,and roving on the Mars.The entry,descent,and landing(EDL)phase directly determines the success of the entire mission,of which the guidance,navigation,and control(GNC)system is crucial.This paper outlines the Tianwen-1 EDL GNC system design by introducing the GNC requirements followed by presenting the GNC system architecture and algorithms to meet such requirements.The actual flight results for the whole EDL phase are also provided in this paper.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51773025 and 21701168)the Natural Foundation of Liaoning Province(Materials Joint Foundation,No.20180510027)+1 种基金Dalian Science and Technology Innovation Fund(No.019J12GX032)We gratefully acknowledge the BL14W1 Beamline of Shanghai Synchrotron Radiation Facility(SSRF)in Shanghai,China and the 1W1B Beamline of Beijing Synchrotron Radiation Facility(BSRF)in Beijing,China for providing the beam time.
文摘Impeding high temperature sintering is challengeable for synthesis of carbon-supported single-atom catalysts (C-SACs), which requires high-cost precursor and strictly-controlled procedures. Herein, by virtue of the ultrastrong polarity of salt melts, sintering of metal atoms is effectively suppressed. Meanwhile, doping with inorganic sulfur anions not only produces sufficient anchoring sites to achieve high loading of atomically dispersed Co up to 13.85 wt.%, but also enables their electronic and geometric structures to be well tuned. When served as a cathode catalyst in dye-sensitized solar cells, the C-SAC with Co-N4-S2 moieties exhibits high activity towards the iodide reduction reaction (IRR), achieving a higher power conversion efficiency than that of conventional Pt counterpart. Density function theory (DFT) calculations revealed that the superior IRR activity was ascribed to the unique structure of Co-N4-S2 moieties with lower reaction barriers and moderate binding energy of iodine on the Co center, which was beneficial to I2 dissociation.
基金This work was supported by the National Natural Science Foundation of China (Nos. 21404018, 21503030) and the Fundamental Research Funds for the Central Universities (No. DUT16RC(4)79). Gaohong He gratefully acknowledges Education Department of the Liaoning Province of China (No. LT2015007), the Fundamental Research Funds for the Central Universi- ties (No. DUT16TD19) and the Chang Jiang Scholar Program (No. T2012049).
基金The financial support of the Natural Science Foundation of China(Nos.21137001 and 21373042)the Fundamental Research Funds for the Central Universities of China(DUT13RC(3)013)Chinese Scholarship Council(CSC)China and for the financial support
文摘Sulfamethoxypyridazine(SMP) is one of the commonly used sulfonamide antibiotics(SAs).SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic environmental organic pollutants.In this work,SMP was selected as a representative of SAs.We studied the mechanisms of triplet-sensitized photodegradation of SMP and the influence of selected dissolved inorganic matter,i.e.,anions(Br^-,Cl^-,and NO^-_3) and cations ions(Ca^(2+),Mg^(2+),and Zn^(2+)) on SMP photodegradation mechanism by quantum chemical methods.In addition,the degradation mechanisms of SMP by hydroxyl radical(OH·) were also investigated.The creation of SO_2 extrusion product was accessed with two different energy pathways(pathway-1 and pathway-2) by following two steps(step-I and step-II) in the tripletsensitized photodegradation of SMP.Due to low activation energy,the pathway-1 was considered as the main pathway to obtain SO_2 extrusion product.Step-II of pathway-1 was measured to be the rate-limiting step(RLS) of SMP photodegradation mechanism and the effect of the selected anions and cations was estimated for this step.All selected anions and cations promoted photodegradation of SMP by dropping the activation energy of pathway-1.The estimated low activation energies of different degradation pathways of SMP with OH·radical indicate that OH·radical is a very powerful oxidizing agent for SMP degradation via attack through benzene derivative and pyridazine derivative ring.
基金financially supported by the National Natural Science Foundation of China (No. 21404018)Fundamental Research Funds for the Central Universities (No. DUT16RC(4)79)+2 种基金Education Department of the Liaoning Province (No. LT2015007)Fundamental Research Funds for the Central Universities (No. DUT16TD19)Chang Jiang Scholar Program (No. T2012049)
文摘The stability of anion exchange membranes(AEMs) is an important feature of alkaline exchange membrane fuel cells(AEMFCs), which has been extensively studied. However it remains a real challenge due to the harsh working condition. Herein, we developed a novel type of polysulfone-based AEMs with three modified 1,2-dimethylbenzimidazoliums containing different substitutes at C4-and C7-position. The results showed that the introduction of the substitutes could obviously improve the dimensional and alkaline stabilities of the corresponding membranes. The swelling ratios of resultant AEMs were all lower than 10% after water immersion. The membrane with 4,7-dimethoxy-1,2-dimethylbenzimidazolium group exhibited the highest alkaline stability. Only 9.2% loss of hydroxide conductivity was observed after treating the membrane in 1 mol·L^(-1) KOH solution at 80 °C for 336 h. Furthermore, the density functional theory(DFT) study on the three functional group models showed that the substitutes at C4-and C7-position affected the lowest unoccupied molecular orbital(LUMO) energies of the different 1,2-dimethylbenzimidazolium groups.
基金the financial support from the National Natural Science Foundation of China(No.21473192)the financial support from the National Natural Science Foundation of China(Nos.21373042 and 21677029)
文摘All-inorganic cesium lead halide perovskites(CsPbX_3, X = Cl^-,Br^-, I^-) could provide comparable optoelectronic properties as a promising class of materials for photovoltaic cell(PV), photodetector and light-emitting diode(LED) with enhanced thermal and moisture stabilities compared to organicinorganic lead halide species. However, fabrication of CsPbI_3 perovskite via facile solution process has been difficult due to instability of CsPbI_3 in the perovskite cubic phase in ambient air. Herein, we report the synthesis of CsPbI_3 perovskite microcrystals by low-temperature, catalyst-free, solution-phase method. By applying the time-resolve spectroscopic technique, we determine the carrier diffusion coefficient of 0.6–1.2 cm^2/s, the intrinsic carrier lifetimes of 200–1300 ns and diffusion length of 4–10μm in different individual CsPbI_3 perovskite microcrystals. Our results suggest the CsPbI_3 perovskite microcrystals synthesized by solution process exhibit high quality feature and are suitable for applications in optoelectronic devices.