The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these c...The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.展开更多
Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms.Usually,they suffer from low intrinsic electronic and ion conduc...Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms.Usually,they suffer from low intrinsic electronic and ion conductivities of the active materials.Here,taking advantage of the combination of TiS2 decoration,sulfur doping,and a nanometer-sized structure,as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons,and exhibit enhanced pseudo-capacitively dominated capacities.At a scan rate of 0.5 mV s−1,a high pseudo-capacitive contribution(76%of the total storage)is obtained for the S-doped TiS2/TiO2/C electrode(termed as TiS2/S-TiO2/C).Such enhanced pseudocapacitive activity allows rapid chemical kinetics and significantly improves the high-rate sodium storage performance of TiO2.The TiS2/S-TiO2/C composite electrode delivers a high capacity of 114 mAh g−1 at a current density of 5000 mA g−1.The capacity maintains at high level(161 mAh g−1)even after 1500 cycles and is still characterized by 58 mAh g−1 at the extreme condition of 10,000 mA g−1 after 10,000 cycles.展开更多
Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization effici...Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster(the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2-CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μmol gMo2C-1s-1 at 400 ℃ with a superior selectivity toward CO(> 99.5%). This work 2 highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.展开更多
Given the advantages of being abundant in resources,environmental benign and highly safe,rechargeable zinc-ion batteries(ZIBs)enter the global spotlight for their potential utilization in large-scale energy storage.De...Given the advantages of being abundant in resources,environmental benign and highly safe,rechargeable zinc-ion batteries(ZIBs)enter the global spotlight for their potential utilization in large-scale energy storage.Despite their preliminary success,zinc-ion storage that is able to deliver capacity>400 mAh g^-1 remains a great challenge.Here,we demonstrate the viability of NH4V4O10(NVO)as high-capacity cathode that breaks through the bottleneck of ZIBs in limited capacity.The first-principles calculations reveal that layered NVO is a good host to provide fast Zn^2+ions diffusion channel along its[010]direction in the interlayer space.On the other hand,to further enhance Zn^2+ion intercalation kinetics and long-term cycling stability,a three-dimensional(3D)flower-like architecture that is self-assembled by NVO nanobelts(3D-NVO)is rationally designed and fabricated through a microwave-assisted hydrothermal method.As a result,such 3D-NVO cathode possesses high capacity(485 mAh g^-1)and superior long-term cycling performance(3000 times)at 10 A g^-1(~50 s to full discharge/charge).Additionally,based on the excellent 3D-NVO cathode,a quasi-solid-state ZIB with capacity of 378 mAh g^-1is developed.展开更多
A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron...A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron microscopy,and temperature‐programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism.Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading.Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface,which had a significant impact on the interaction between Ru and adsorbed H,and concomitantly,the H2activation capacity via the ability for H2dissociation.FeOx having0.01%of Ru loading exhibited100%selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H,which limits the desorption of the activated H species and hinders over‐reduction of CO to CH4.Further increasing the Ru loading of the catalysts to above0.01%resulted in the adsorbed H to be easily dissociated,as a result of a weaker interaction with Ru,which allowed excessive CO reduction to produce CH4.Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
Solid physical properties are vital for the design, optimization, and scale-up of gas–liquid–solid multiphase reactors. The complex and interactional effects of the solid physical properties, including particle diam...Solid physical properties are vital for the design, optimization, and scale-up of gas–liquid–solid multiphase reactors. The complex and interactional effects of the solid physical properties, including particle diameter, density, wettability, and sphericity, on the hydrodynamic behaviors in a new external airlift loop reactor(EALR) integrating mixing and separation are decoupled in this work. Two semi-empirical equations are proposed and validated to predict the overall gas holdup and liquid circulating velocity satisfactorily, and then the individual influence of such solid physical properties is further investigated. The results demonstrate that both the overall gas holdup in the riser and the liquid circulating velocity in the downcomer increase with the contact angle, but decrease with particle size, density, and sphericity.Additionally, the impact of the particle size on the liquid circulating velocity is also profoundly revealed on a micro-level considering the particle size distribution. Moreover, the axial solid concentration distribution is discussed, and the uniformity of the slurry is described by the mixing index of the solid particles. The results show that a more homogeneous mixture can be achieved by adding finer particles other than attaining violent turbulence. Therefore, this work lays a foundation for the design, scale-up, and industrialization of the EALRs.展开更多
Potassium-selenium(K-Se)batteries have attracted more and more attention because of their high theoretical specific capacity and natural abundance of K resources.However,dissolution of polyselenides,large volume expan...Potassium-selenium(K-Se)batteries have attracted more and more attention because of their high theoretical specific capacity and natural abundance of K resources.However,dissolution of polyselenides,large volume expansion during cycling and low utilization of Se remain great challenges,leading to poor rate capability and cycle life.Herein,N/O dual-doped carbon nanofibers with interconnected micro/mesopores(MMCFs)are designed as hosts to manipulate Se molecular configuration for advanced flexible K-Se batteries.The micropores play a role in confining small Se molecule(Se_(2–3)),which could inhibit the formation of polyselenides and work as physical barrier to stabilize the cycle performance.While the mesopores can confine long-chain Se(Se_(4–7)),promising sufficient Se loading and contributing to higher discharge voltage of the whole Se@MMCFs composite.The N/O co-doping and the 3D interpenetrating nanostructure improve electrical conductivity and keep the structure integrity after cycling.The obtained Se_(2–3)/Se_(4–7)@MMCFs electrode exhibits an unprecedented cycle life(395 mA h g^(−1) at 1 A g^(−1) after 2000 cycles)and high specific energy density(400 Wh kg^(−1),nearly twice the specific energy density of the Se_(2–3)@MMCFs).This study offers a rational design for the realization of a high energy density and long cycle life chalcogen cathode for energy storage.展开更多
Solid‐state Zn–air batteries(ZABs)hold great potential for application in wearable and flexible electronics.However,further commercialization of current ZABs is still limited by the poor stability and low energy eff...Solid‐state Zn–air batteries(ZABs)hold great potential for application in wearable and flexible electronics.However,further commercialization of current ZABs is still limited by the poor stability and low energy efficiency.It is,thus,crucial to develop efficient catalysts as well as optimize the solid electrolyte system to unveil potential of the ZAB technology.Due to the low cost and versatility in tailoring the structures and properties,carbon materials have been extensively used as the conductive substrates,catalytic air electrodes,and important components in the electrolytes for the solid‐state ZABs.Within this context,we discuss the challenges facing current solid‐state ZABs and summarize the strategies developed to modify properties of carbon‐based electrodes and electrolytes.We highlight the metal−organic framework/covalent organic framework‐based electrodes,heteroatom‐doped carbon,and the composites formed of carbon with metal oxides/sulfides/phosphides.We also briefly discuss the progress of graphene oxide‐based solid electrolyte.展开更多
The discovery of novel electrode materials promises to unleash a number of technological advances in lithium-ion batteries.V2O5 is recognized as a high-performance cathode that capitalizes on the rich redox chemistry ...The discovery of novel electrode materials promises to unleash a number of technological advances in lithium-ion batteries.V2O5 is recognized as a high-performance cathode that capitalizes on the rich redox chemistry of vanadium to store lithium.To unlock the full potential of V2O5,nanotechnology solution and rational electrode design are used to imbue V2O5 with high energy and power density by addressing some of their intrinsic disadvantages in macroscopic crystal form.Here,we demonstrate a facile and environmental-friendly method to prepare nanorods-constructed 3D porous V2O5 architectures(3 D-V2O5)in large-scale.The 3D porous architecture is found to be responsible for the enhanced charge transfer kinetics and Li-ion diffusion rate of the 3D-V2O5 electrode.As the result,the 3D-V2O5 surpasses the conventional bulk V2O5 by showing enhanced discharge capacity and rate capability(delivering 154 and 127 m Ah g^-1 at 15 and 20 C,respectively).展开更多
Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and ...Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53（S-MIL-53）and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.展开更多
Alkali metal ion batteries(AMIBs)are playing an irreplaceable part in the energy revolution,due to their intrinsic advantages of large capacity/power density and abundance of alkali metal ions in the earth’s crust.De...Alkali metal ion batteries(AMIBs)are playing an irreplaceable part in the energy revolution,due to their intrinsic advantages of large capacity/power density and abundance of alkali metal ions in the earth’s crust.Despite their great promise,the inborn deficiencies of commercial graphite and other anodes being researched so far call for the quest of better alternatives that exhibit all-round performance with the balance of energy/power density and cycling stability.Gallium-based materials,with impressive capacity utilization and self-healing ability,provide an anticipated solution to this conundrum.In this review,an overview on the recent progress of gallium-based anodes and their storage mechanism is presented.The current strategies used as engineering solutions to meet the scientific challenges ahead are discussed,in addition to the insightful outlook for possible future study.展开更多
A new developed external loop airlift slurry reactor, which was integrated with gas–liquid–solid three-phase mixing, mass transfer, and liquid–solid separation simultaneously, was deemed to be a promising slurry re...A new developed external loop airlift slurry reactor, which was integrated with gas–liquid–solid three-phase mixing, mass transfer, and liquid–solid separation simultaneously, was deemed to be a promising slurry reactor due to its prominent advantages such as achieving continuous separation of clear liquid from slurry and cyclic utilization of solid particles without any extra energy, energy-saving, and intrinsic safety design. The principal operating parameters, including gas separator volume, handling capacity, and superficial gas velocity, are systematically investigated here to promote the capabilities of mixing, mass transfer, and yield in the pilot external loop airlift slurry reactor. The influences of top clearance and throughput of the clear liquid on flow regime and gas holdup in the riser, liquid circulating velocity, and volumetric mass transfer coefficient with a typical high solid holdup and free of particles are examined experimentally. It was found that increasing the gas separator volume could promote the liquid circulating velocity by about 14.0% at most. Increasing the handling capacity of the clear liquid from 0.9 m3·h-1 to 3.0 m3·h-1 not only could increase the output without any adverse consequences, but also could enhance the liquid circulating velocity as much as 97.3%. Typical operating conditions investigated here can provide some necessary data and guidelines for this new external loop airlift slurry reactor to upgrade its performances.展开更多
Selectively converting CO and H2 to gasoline product （isoparaffin and olefin） in one step still remains a great challenge. We demonstrate effective H-USY zeolite supported nano-cobalt bifunctional catalysts for this...Selectively converting CO and H2 to gasoline product （isoparaffin and olefin） in one step still remains a great challenge. We demonstrate effective H-USY zeolite supported nano-cobalt bifunctional catalysts for this catalytic reaction, which are prepared by the novel physical sputtering process. Particles of the sputtered cobalt exist in nano-level and are well-dispersed on acid USY zeolite. Easy activation of the loaded nano-cobalt is also achieved in a low-temperature hydrogen reduction atmosphere. In the tandem catalytic reaction, the sputtered bifunctional Co/USY catalyst exhibits a much higher CO conversion and higher isoparaffin selectiv- ity than the conventional impregnated one. Compared with H-Mor, H-Beta and other zeolites supported catalysts, H-USY zeolite supported cobalt catalyst shows the clearest promotional effect on the activity of FischerTropsch synthesis. The described synthesis herein provides a new pathway to solve the problem caused by the strong metal-support interaction （MSI） in heterogeneous catalysis.展开更多
A membrane with high stability and ion conductivity in wide pH range is essential for energy storage devices.Here,we report a novel membrane with hierarchical core-shell structure,which demonstrates high stability and...A membrane with high stability and ion conductivity in wide pH range is essential for energy storage devices.Here,we report a novel membrane with hierarchical core-shell structure,which demonstrates high stability and ion conductivity,simultaneously under a wide pH range applications.Spectral characterizations and theoretical calculation indicate that the non-solvent induces the chain segment configuration and eventually leads to polymer-polymer phase separation,thus forming hierarchical porous core-shell structure.Benefiting from this structure,an acidic vanadium flow battery(VFB)with such a membrane shows excellent performance over 400 cycles with an energy efficiency(EE)of above 81%at current density of 120 mA cm^(-2) and an alkaline zinc-iron flow battery(AZIFB)delivers a cycling stability for more than 200 cycles at 160 mA cm^(-2),along with an EE of above 82%.This paper provides a cost-effective and simple way to fabricate membranes with high performance for variety of energyrelated devices.展开更多
Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane cont...Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.展开更多
Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However...Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.展开更多
Sodium-ion batteries(SIBs)have become an auspicious candidate for largescale energy storage by cause of low cost,natural abundance,and similar working principle with lithium-ion batteries(LIBs).At present,there is an ...Sodium-ion batteries(SIBs)have become an auspicious candidate for largescale energy storage by cause of low cost,natural abundance,and similar working principle with lithium-ion batteries(LIBs).At present,there is an urgent need to explore superior anode materials with rapid and stable sodiation/desodiation.Herein,3D self-assembled VS4 curly nanosheets hierarchitectures(VS4-CN-Hs)are developed for SIB anodes,where VS4 possesses a large theoretical sodium storage capacity,and the building block of nanosheets has large exposed surface area to the electrolyte as well as the constructed hierarchitectures can provide abundant buffer space to alleviate the volume expansion.As a result,VS4-CN-Hs anode possesses excellent electrochemical performance under a wide voltage window of 0.01–3.0 V,such as high reversible capacity of 863 mA h g^(−1) at 0.1 A g^(−1),marvelous rate feature(444 mA h g^(−1) at 10 A g^(−1)),and extralong cycle stability(386 mA h g^(−1) after 1000 times at 5 A g^(−1)).展开更多
Aqueous rechargeable metal-ion batteries(ARMBs)hold intrinsic advantages of high safety,low cost and environmental benignity for large scale energy storage technologies.However,the research on aqueous Kion batteries(A...Aqueous rechargeable metal-ion batteries(ARMBs)hold intrinsic advantages of high safety,low cost and environmental benignity for large scale energy storage technologies.However,the research on aqueous Kion batteries(AKIBs)was hindered by limited materials.Herein,a novel AKIB was reported by employing environment-friendly 1,4,5,8-naphthalenetetracarboxylic dianhydride-derived polyimide(PNTCDA)as anode and Berlin green(FeHCF)as cathode.Both electrodes have high rate performance and excellent capacity retention during cycling.Kinetics researches verify the superior electrochemical property of PNTCDA in saturated KNO3 solution.In-situ XRD of FeHCF demonstrates the unique shift of peak position and negligible distortion of lattice during the insertion/extraction of K+.The AKIB exhibits an attractive energy density of 46.9 Wh/kg and a high capacity retention of 74%in 300 cycles.More importantly,the battery can reach a super-high power of 2079.1 W/kg with an energy density of 24.2 Wh/kg,ranking relatively high among the ARIMs.This system extends the use of polyimide and points a way of AKIBs for grid-scale energy storage.展开更多
A sustainable strategy for Fischer–Tropsch iron catalysts is successfully achieved by embedding of synergistic promoters from a renewable resource, corncob. The iron-based catalysts, named as 'corncob-driven'...A sustainable strategy for Fischer–Tropsch iron catalysts is successfully achieved by embedding of synergistic promoters from a renewable resource, corncob. The iron-based catalysts, named as 'corncob-driven'catalysts, are composed of iron species supported on carbon as primary active components and various minerals(K, Mg, Ca, and Si, etc.) as promoters. The corncob-driven catalysts are facilely synthesized by a one-pot hydrothermal treatment under mild conditions. The characterization results indicate that the formation of iron carbides from humboldtine is clearly enhanced and the morphology of catalyst particles tends to be more regular microspheres after adding corncob. It is observed that the optimized corncob-driven catalyst exhibits a higher conversion than without promoters' catalyst in Fischer–Tropsch synthesis(ca. 73% vs. ca. 49%). More importantly, a synergistic effect exists in multiple promoters from corncob that can enhance heavy hydrocarbons selectivity and lower CO_2 selectivity, obviously different from the catalyst with promoters from chemicals. The proposed synthesis route of corncob-driven catalysts provides new strategies for the utilization of renewable resources and elimination of environmental pollutants from chemical promoters.展开更多
基金supported by Shanxi Province Science Foundation for Youths(202203021212300)Taiyuan University of Science and Technology Scientific Research Initial Funding(20212064)Outstanding Doctoral Award Fund in Shanxi Province(20222060).
文摘The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.
基金This work was financially supported by National Key R&D Program of China(No.2018YFB0905400)the National Natural Science Foundation of China(Nos.51925207,51872277,and U1910210)+2 种基金Dalian National Laboratory For Clean Energy(DNL)Cooperation Fund,the CAS(DNL180310)the Fundamental Research Funds for the Central Universities(Wk2060140026)Sofja Kovalevskaja award of the Humboldt Society.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No.823717-ESTEEM3.
文摘Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms.Usually,they suffer from low intrinsic electronic and ion conductivities of the active materials.Here,taking advantage of the combination of TiS2 decoration,sulfur doping,and a nanometer-sized structure,as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons,and exhibit enhanced pseudo-capacitively dominated capacities.At a scan rate of 0.5 mV s−1,a high pseudo-capacitive contribution(76%of the total storage)is obtained for the S-doped TiS2/TiO2/C electrode(termed as TiS2/S-TiO2/C).Such enhanced pseudocapacitive activity allows rapid chemical kinetics and significantly improves the high-rate sodium storage performance of TiO2.The TiS2/S-TiO2/C composite electrode delivers a high capacity of 114 mAh g−1 at a current density of 5000 mA g−1.The capacity maintains at high level(161 mAh g−1)even after 1500 cycles and is still characterized by 58 mAh g−1 at the extreme condition of 10,000 mA g−1 after 10,000 cycles.
基金the National Natural Science Foundation of China(21872144,21972140 and 91645117)Liaoning Revitalization Talents Program(XLYC1907053)+2 种基金CAS Youth Innovation Promotion Association(2018220)Talents Innovation Project of Dalian City(2017RQ032 and 2016RD04)China Postdoctoral Science Foundation(2019TQ0314,2018M641726 and 2019M661146)。
文摘Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster(the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2-CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μmol gMo2C-1s-1 at 400 ℃ with a superior selectivity toward CO(> 99.5%). This work 2 highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.
基金the National Key R&D Research Program of China(Grant No.2018YFB0905400)National Natural Science Foundation of China(Grant Nos.51622210,51872277,51802007,21606003,51972067,51802044,51672193,51420105002,51920105004,and U1910210)+3 种基金the Fundamental Research Funds for the Central Universities(WK2060140026)Guangdong Natural Science Funds for Distinguished Young Scholar(Grant No.2019B151502039)the DNL Cooperation Fund,CAS(DNL180310)Opening Project of CAS Key Laboratory of Materials for Energy Conversion.
文摘Given the advantages of being abundant in resources,environmental benign and highly safe,rechargeable zinc-ion batteries(ZIBs)enter the global spotlight for their potential utilization in large-scale energy storage.Despite their preliminary success,zinc-ion storage that is able to deliver capacity>400 mAh g^-1 remains a great challenge.Here,we demonstrate the viability of NH4V4O10(NVO)as high-capacity cathode that breaks through the bottleneck of ZIBs in limited capacity.The first-principles calculations reveal that layered NVO is a good host to provide fast Zn^2+ions diffusion channel along its[010]direction in the interlayer space.On the other hand,to further enhance Zn^2+ion intercalation kinetics and long-term cycling stability,a three-dimensional(3D)flower-like architecture that is self-assembled by NVO nanobelts(3D-NVO)is rationally designed and fabricated through a microwave-assisted hydrothermal method.As a result,such 3D-NVO cathode possesses high capacity(485 mAh g^-1)and superior long-term cycling performance(3000 times)at 10 A g^-1(~50 s to full discharge/charge).Additionally,based on the excellent 3D-NVO cathode,a quasi-solid-state ZIB with capacity of 378 mAh g^-1is developed.
基金supported by the National Natural Science Foundation of China(21476145,91645117)China Postdoctoral Science Foundation(2016M600221)~~
文摘A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron microscopy,and temperature‐programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism.Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading.Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface,which had a significant impact on the interaction between Ru and adsorbed H,and concomitantly,the H2activation capacity via the ability for H2dissociation.FeOx having0.01%of Ru loading exhibited100%selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H,which limits the desorption of the activated H species and hinders over‐reduction of CO to CH4.Further increasing the Ru loading of the catalysts to above0.01%resulted in the adsorbed H to be easily dissociated,as a result of a weaker interaction with Ru,which allowed excessive CO reduction to produce CH4.Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
基金supported by the National Natural Science Foundation of China (21878318, 22108285)the DNL Cooperation Fund, CAS (DNL201902)+2 种基金“Transformational Technologies for Clean Energy and Demonstration”, Strategic Priority Research Program of the Chinese Academy of Sciences (CAS) (XDA21060400)Shandong Energy Institute, Single-Cell Center Project (SCZ-16, SCZ17)Director Innovation Fund of Synthetic Biology Technology Innovation Center of Shandong Province (sdsynbio-2020-ZH-02)。
文摘Solid physical properties are vital for the design, optimization, and scale-up of gas–liquid–solid multiphase reactors. The complex and interactional effects of the solid physical properties, including particle diameter, density, wettability, and sphericity, on the hydrodynamic behaviors in a new external airlift loop reactor(EALR) integrating mixing and separation are decoupled in this work. Two semi-empirical equations are proposed and validated to predict the overall gas holdup and liquid circulating velocity satisfactorily, and then the individual influence of such solid physical properties is further investigated. The results demonstrate that both the overall gas holdup in the riser and the liquid circulating velocity in the downcomer increase with the contact angle, but decrease with particle size, density, and sphericity.Additionally, the impact of the particle size on the liquid circulating velocity is also profoundly revealed on a micro-level considering the particle size distribution. Moreover, the axial solid concentration distribution is discussed, and the uniformity of the slurry is described by the mixing index of the solid particles. The results show that a more homogeneous mixture can be achieved by adding finer particles other than attaining violent turbulence. Therefore, this work lays a foundation for the design, scale-up, and industrialization of the EALRs.
基金This work was supported by the National Key R&D Research Program of China(Nos.2018YFA0209600,2017YFA0208300)the National Natural Science Foundation of China(Nos.51925207,U1910210,51872277,52002083,22005292,51802302)+4 种基金the DNL cooperation Fund,CAS(DNL180310)the Fundamental Research Funds for the Central Universities(WK2060140026,WK3430000006,WK2060000009)the National Synchrotron Radiation Laboratoi-y(KY2060000173)the National Postdoctoral Program for Innovative Talents(BX20200318)the China Postdoctoral Science Foundation(Nos.2020M672533,2019TQ0296,2020M682012).
文摘Potassium-selenium(K-Se)batteries have attracted more and more attention because of their high theoretical specific capacity and natural abundance of K resources.However,dissolution of polyselenides,large volume expansion during cycling and low utilization of Se remain great challenges,leading to poor rate capability and cycle life.Herein,N/O dual-doped carbon nanofibers with interconnected micro/mesopores(MMCFs)are designed as hosts to manipulate Se molecular configuration for advanced flexible K-Se batteries.The micropores play a role in confining small Se molecule(Se_(2–3)),which could inhibit the formation of polyselenides and work as physical barrier to stabilize the cycle performance.While the mesopores can confine long-chain Se(Se_(4–7)),promising sufficient Se loading and contributing to higher discharge voltage of the whole Se@MMCFs composite.The N/O co-doping and the 3D interpenetrating nanostructure improve electrical conductivity and keep the structure integrity after cycling.The obtained Se_(2–3)/Se_(4–7)@MMCFs electrode exhibits an unprecedented cycle life(395 mA h g^(−1) at 1 A g^(−1) after 2000 cycles)and high specific energy density(400 Wh kg^(−1),nearly twice the specific energy density of the Se_(2–3)@MMCFs).This study offers a rational design for the realization of a high energy density and long cycle life chalcogen cathode for energy storage.
基金This study was financially supported by the National Key R&D Research Program of China(Grant No.2018YFB0905400)National Natural Science Foundationof China(Grant Nos.,51925207,U1910210,51972067,51802044,and 51872277)+2 种基金Guangdong Natural Science Funds for Distinguished Young Scholar(Grant No.2019B151502039)Fundamental Research Funds for the Central Universities of China(Grant No.WK2060140026)the DNL Cooperation Fund,CAS(Grant No.DNL180310).
文摘Solid‐state Zn–air batteries(ZABs)hold great potential for application in wearable and flexible electronics.However,further commercialization of current ZABs is still limited by the poor stability and low energy efficiency.It is,thus,crucial to develop efficient catalysts as well as optimize the solid electrolyte system to unveil potential of the ZAB technology.Due to the low cost and versatility in tailoring the structures and properties,carbon materials have been extensively used as the conductive substrates,catalytic air electrodes,and important components in the electrolytes for the solid‐state ZABs.Within this context,we discuss the challenges facing current solid‐state ZABs and summarize the strategies developed to modify properties of carbon‐based electrodes and electrolytes.We highlight the metal−organic framework/covalent organic framework‐based electrodes,heteroatom‐doped carbon,and the composites formed of carbon with metal oxides/sulfides/phosphides.We also briefly discuss the progress of graphene oxide‐based solid electrolyte.
基金the National Key R&D Research Program of China (No. 2018YFB0905400)the National Natural Science Foundation of China (Grant Nos. 51622210, 51872277, 21606003 and 51802044)+2 种基金the DNL cooperation Fund, CAS (DNL180310)the Fundamental Research Funds for the Central Universities (WK3430000004)Opening Projects of CAS Key Laboratory of Materials for Energy Conversion and State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization
文摘The discovery of novel electrode materials promises to unleash a number of technological advances in lithium-ion batteries.V2O5 is recognized as a high-performance cathode that capitalizes on the rich redox chemistry of vanadium to store lithium.To unlock the full potential of V2O5,nanotechnology solution and rational electrode design are used to imbue V2O5 with high energy and power density by addressing some of their intrinsic disadvantages in macroscopic crystal form.Here,we demonstrate a facile and environmental-friendly method to prepare nanorods-constructed 3D porous V2O5 architectures(3 D-V2O5)in large-scale.The 3D porous architecture is found to be responsible for the enhanced charge transfer kinetics and Li-ion diffusion rate of the 3D-V2O5 electrode.As the result,the 3D-V2O5 surpasses the conventional bulk V2O5 by showing enhanced discharge capacity and rate capability(delivering 154 and 127 m Ah g^-1 at 15 and 20 C,respectively).
基金the financial support from the National Natural Science Foundation of China(No.21436009)
文摘Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53（S-MIL-53）and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.
基金the National Key R&D Research Program of China(Grant No.2018YFB0905400)the National Natural Science Foundation of China(Grant Nos.51872277,21606003,51902062,51972067,51802044,51925207 and U1910210)+2 种基金the Fundamental Research Funds for the Central Universities(WK2060140026)the DNL cooperation Fund,CAS(DNL180310)the Guangdong Natural Science Funds for Distinguished Young Scholar(Grant No.2019B151502039)。
文摘Alkali metal ion batteries(AMIBs)are playing an irreplaceable part in the energy revolution,due to their intrinsic advantages of large capacity/power density and abundance of alkali metal ions in the earth’s crust.Despite their great promise,the inborn deficiencies of commercial graphite and other anodes being researched so far call for the quest of better alternatives that exhibit all-round performance with the balance of energy/power density and cycling stability.Gallium-based materials,with impressive capacity utilization and self-healing ability,provide an anticipated solution to this conundrum.In this review,an overview on the recent progress of gallium-based anodes and their storage mechanism is presented.The current strategies used as engineering solutions to meet the scientific challenges ahead are discussed,in addition to the insightful outlook for possible future study.
基金supported by the National Natural Science Foundation of China (Nos. 21808234,21878318)the DNL Cooperation Fund,CAS(DNL201902)+3 种基金“Transformational Technologies for Clean Energy and Demonstration”, Strategic Priority Research Program of the CAS(XDA21060400)QIBEBT and Dalian National Laboratory for Clean Energy of the CAS(QIBEBT ZZBS201803,QIBEBT I201907)CAS Key Technology Talent ProgramProject of CNPC-DICP Joint Research Center。
文摘A new developed external loop airlift slurry reactor, which was integrated with gas–liquid–solid three-phase mixing, mass transfer, and liquid–solid separation simultaneously, was deemed to be a promising slurry reactor due to its prominent advantages such as achieving continuous separation of clear liquid from slurry and cyclic utilization of solid particles without any extra energy, energy-saving, and intrinsic safety design. The principal operating parameters, including gas separator volume, handling capacity, and superficial gas velocity, are systematically investigated here to promote the capabilities of mixing, mass transfer, and yield in the pilot external loop airlift slurry reactor. The influences of top clearance and throughput of the clear liquid on flow regime and gas holdup in the riser, liquid circulating velocity, and volumetric mass transfer coefficient with a typical high solid holdup and free of particles are examined experimentally. It was found that increasing the gas separator volume could promote the liquid circulating velocity by about 14.0% at most. Increasing the handling capacity of the clear liquid from 0.9 m3·h-1 to 3.0 m3·h-1 not only could increase the output without any adverse consequences, but also could enhance the liquid circulating velocity as much as 97.3%. Typical operating conditions investigated here can provide some necessary data and guidelines for this new external loop airlift slurry reactor to upgrade its performances.
基金Financial aid from NEDO (Japan)the National Natural Science Foundation of China (21503215)
文摘Selectively converting CO and H2 to gasoline product （isoparaffin and olefin） in one step still remains a great challenge. We demonstrate effective H-USY zeolite supported nano-cobalt bifunctional catalysts for this catalytic reaction, which are prepared by the novel physical sputtering process. Particles of the sputtered cobalt exist in nano-level and are well-dispersed on acid USY zeolite. Easy activation of the loaded nano-cobalt is also achieved in a low-temperature hydrogen reduction atmosphere. In the tandem catalytic reaction, the sputtered bifunctional Co/USY catalyst exhibits a much higher CO conversion and higher isoparaffin selectiv- ity than the conventional impregnated one. Compared with H-Mor, H-Beta and other zeolites supported catalysts, H-USY zeolite supported cobalt catalyst shows the clearest promotional effect on the activity of FischerTropsch synthesis. The described synthesis herein provides a new pathway to solve the problem caused by the strong metal-support interaction （MSI） in heterogeneous catalysis.
基金the financial support from NSFC(21925804,U1808209 and 21908214)CAS Engineering Laboratory for Electrochemical Energy Storage,CAS,STS program.Major scientific and technological innovation project of Shandong(2018YFJH0106)+1 种基金the CAS(DNL201910)Youth Innovation Promotion Association CAS。
文摘A membrane with high stability and ion conductivity in wide pH range is essential for energy storage devices.Here,we report a novel membrane with hierarchical core-shell structure,which demonstrates high stability and ion conductivity,simultaneously under a wide pH range applications.Spectral characterizations and theoretical calculation indicate that the non-solvent induces the chain segment configuration and eventually leads to polymer-polymer phase separation,thus forming hierarchical porous core-shell structure.Benefiting from this structure,an acidic vanadium flow battery(VFB)with such a membrane shows excellent performance over 400 cycles with an energy efficiency(EE)of above 81%at current density of 120 mA cm^(-2) and an alkaline zinc-iron flow battery(AZIFB)delivers a cycling stability for more than 200 cycles at 160 mA cm^(-2),along with an EE of above 82%.This paper provides a cost-effective and simple way to fabricate membranes with high performance for variety of energyrelated devices.
基金the financial support from Dalian Institute of Chemical Physics (DMTO201604)Focus Area Innovation Team Support Plan of Dalian (2021RT03)+1 种基金National Natural Science Foundation of China (21878284)Regional Development Young Scholars of the Chinese Academy of Sciences。
文摘Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.
基金financially supported by Open Fund of Material Corrosion and Protection Key Laboratory of Sichuan Province of China(No.2020CL09)Hunan Key Laboratory of Applied Environmental Photocatalysis(No.2214503)。
文摘Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.
基金the National Natural Science Foundation of China(Grant Nos.51925207,U1910210,51872277,51972067,21606003,51902062,51802043,and 51802044)the Fundamental Research Funds for the Central Universities(WK2060140026)+2 种基金the DNL cooperation Fund,CAS(DNL180310)the National Synchrotron Radiation Laboratory(KY2060000173)Guangdong Natural Science Funds for Distinguished Young Scholar(Grant No.2019B151502039).
文摘Sodium-ion batteries(SIBs)have become an auspicious candidate for largescale energy storage by cause of low cost,natural abundance,and similar working principle with lithium-ion batteries(LIBs).At present,there is an urgent need to explore superior anode materials with rapid and stable sodiation/desodiation.Herein,3D self-assembled VS4 curly nanosheets hierarchitectures(VS4-CN-Hs)are developed for SIB anodes,where VS4 possesses a large theoretical sodium storage capacity,and the building block of nanosheets has large exposed surface area to the electrolyte as well as the constructed hierarchitectures can provide abundant buffer space to alleviate the volume expansion.As a result,VS4-CN-Hs anode possesses excellent electrochemical performance under a wide voltage window of 0.01–3.0 V,such as high reversible capacity of 863 mA h g^(−1) at 0.1 A g^(−1),marvelous rate feature(444 mA h g^(−1) at 10 A g^(−1)),and extralong cycle stability(386 mA h g^(−1) after 1000 times at 5 A g^(−1)).
文摘Aqueous rechargeable metal-ion batteries(ARMBs)hold intrinsic advantages of high safety,low cost and environmental benignity for large scale energy storage technologies.However,the research on aqueous Kion batteries(AKIBs)was hindered by limited materials.Herein,a novel AKIB was reported by employing environment-friendly 1,4,5,8-naphthalenetetracarboxylic dianhydride-derived polyimide(PNTCDA)as anode and Berlin green(FeHCF)as cathode.Both electrodes have high rate performance and excellent capacity retention during cycling.Kinetics researches verify the superior electrochemical property of PNTCDA in saturated KNO3 solution.In-situ XRD of FeHCF demonstrates the unique shift of peak position and negligible distortion of lattice during the insertion/extraction of K+.The AKIB exhibits an attractive energy density of 46.9 Wh/kg and a high capacity retention of 74%in 300 cycles.More importantly,the battery can reach a super-high power of 2079.1 W/kg with an energy density of 24.2 Wh/kg,ranking relatively high among the ARIMs.This system extends the use of polyimide and points a way of AKIBs for grid-scale energy storage.
基金financially supported by the National Natural Science Foundation of China(21503215)
文摘A sustainable strategy for Fischer–Tropsch iron catalysts is successfully achieved by embedding of synergistic promoters from a renewable resource, corncob. The iron-based catalysts, named as 'corncob-driven'catalysts, are composed of iron species supported on carbon as primary active components and various minerals(K, Mg, Ca, and Si, etc.) as promoters. The corncob-driven catalysts are facilely synthesized by a one-pot hydrothermal treatment under mild conditions. The characterization results indicate that the formation of iron carbides from humboldtine is clearly enhanced and the morphology of catalyst particles tends to be more regular microspheres after adding corncob. It is observed that the optimized corncob-driven catalyst exhibits a higher conversion than without promoters' catalyst in Fischer–Tropsch synthesis(ca. 73% vs. ca. 49%). More importantly, a synergistic effect exists in multiple promoters from corncob that can enhance heavy hydrocarbons selectivity and lower CO_2 selectivity, obviously different from the catalyst with promoters from chemicals. The proposed synthesis route of corncob-driven catalysts provides new strategies for the utilization of renewable resources and elimination of environmental pollutants from chemical promoters.
