The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water （HTLW） was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The ma...The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water （HTLW） was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The main products of xylose decomposition were furfural and formic acid, and furfural further degraded to formic acid under HTLW condition. With the assumption of first order kinetics e.quation, the evaluated activation energy of xylose and furfural decomposition was 123.27kJ·mol^-1 and 58.84kJ·mol^-1, respectively.展开更多
Transition metal diborides based ultrahigh temperature ceramics(UHTCs) are characterized by high melting point, high strength and hardness, and high electrical and thermal conductivity. The high thermal conductivity a...Transition metal diborides based ultrahigh temperature ceramics(UHTCs) are characterized by high melting point, high strength and hardness, and high electrical and thermal conductivity. The high thermal conductivity arises from both electronic and phonon contributions. Thus electronic and phonon contributions must be controlled simultaneously in reducing the thermal conductivity of transition metal diborides. In high entropy(HE) materials, both electrons and phonons are scattered such that the thermal conductivity can significantly be reduced, which opens a new window to design novel insulating materials. Inspired by the high entropy effect, porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is designed in this work as a new thermal insulting ultrahigh temperature material and is synthesized by an in-situ thermal borocarbon reduction/partial sintering process. The porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 possesses high porosity of 75.67%, pore size of 0.3–1.2 μm, homogeneous microstructure with small grain size of 400–800 nm, which results in low room temperature thermal diffusivity and thermal conductivity of 0.74 mm2 s^-1 and 0.51 W m^-1K^-1, respectively. In addition, it exhibits high compressive strength of3.93 MPa. The combination of these properties indicates that exploring porous high entropy ceramics such as porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is a novel strategy in making UHTCs thermal insulating.展开更多
The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morpholo...The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.展开更多
The decomposition kinetics of glucose was studied in high-temperature liquid water （HTLW） from 180 to 220℃ under a pressure of 10 MPa. It was found the main products from glucose decomposition were 5-hydroxymethylf...The decomposition kinetics of glucose was studied in high-temperature liquid water （HTLW） from 180 to 220℃ under a pressure of 10 MPa. It was found the main products from glucose decomposition were 5-hydroxymethylfurfural （5-HMF） and levulinic acid （LA）. The decomposition kinetics of 5-HMF and stability of LA in HTLW were further investigated. A kinetic model for glucose decomposition was proposed accordingly. In the model, a series of first-order reactions with the consideration of parallel by-reactions were used to illustrate the decomposition of glucose. The decomposition activation energies of glucose, 5-HMF, and LA were evaluated as 118.85, 95.40, and 31.29 kJ·mol^-1, respectively.展开更多
Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable ...Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.展开更多
Advanced materials for electrocatalytic water splitting applications have been sought-after considering both environmental and economic requirements.However,the traditional materials design concept limits the explorat...Advanced materials for electrocatalytic water splitting applications have been sought-after considering both environmental and economic requirements.However,the traditional materials design concept limits the exploration of high-performance catalysts.The born of a materials design concept based on multiple elements,high-entropy materials,provides a promising path to break the shackles of compositional design in materials science.A number of high-entropy materials were reported to show remarkable properties for electrocatalytic water splitting applications.High-entropy materials were widely confirmed to be one kind of the best electrocatalysts for water splitting applications.Due to the synergy of multiple metal components,they show excellent catalytic activity.Several nontraditional methods were developed and reported to prepare high-performance high-entropy materials.This review article presents the recent progress on high-entropy materials for electrocatalytic water splitting applications.Moreover,it presents the research interests and future prospects in this field.展开更多
Developing efficient,stable and economical electrocatalyst for oxygen evolution reaction(OER)is a significant pathway to produce clean energy from water splitting.Herein,the promising and highly efficient porous CoCrF...Developing efficient,stable and economical electrocatalyst for oxygen evolution reaction(OER)is a significant pathway to produce clean energy from water splitting.Herein,the promising and highly efficient porous CoCrFeNiMo high entropy alloys(HEAs)were prepared by microwave sintering using Mg space holder.Owing to unique properties of high entropy alloys and abundant active surface area,the porous CoCrFeNiMo-20 Mg exhibits excellent catalytic performance and prominent electrochemical stability with a low overpotential of 220 mV to reach current density of 10 mA cm^(-2),a small Tafel slope of 59.0 mV dec^(-1) and long-term durability for 24 h in 1.0 M KOH.The results of microstructure and element states indicate that crystal defects,porous structure and villous hydroxides are the reasons for high OER performance of the CoCrFeNiMo.This work not only provides a new way to prepare electrocatalysts,but also proves the important application of high entropy alloys in functional materials.展开更多
Oxygen evolution reaction(OER)is the key step involved both in water splitting devices and rechargeable metal-air batteries,and hence,there is an urgent need for a stable and low-cost material for efficient OER.In the...Oxygen evolution reaction(OER)is the key step involved both in water splitting devices and rechargeable metal-air batteries,and hence,there is an urgent need for a stable and low-cost material for efficient OER.In the present investigation,Co-Fe-Ga-NiZn(CFGNZ)high entropy alloy(HEA)has been utilized as a low-cost electrocatalyst for OER.Herein,after cyclic voltammetry activation,CFGNZ-nanoparticles(NPs)are covered with oxidized surface and form high entropy(oxy)hydroxides(HEOs),exhibiting a low overpotential of 370 mV to achieve a current density of 10 mA/cm^(2)with a small Tafel slope of 71 mV/dec.CFGNZ alloy has higher electrochemical stability in comparison to state-of-the art RuO2 electrocatalyst as no degradation has been observed up to 10 h of chronoamperometry.Transmission electron microscopy(TEM)studies after 10 h of long-term chronoamperometry test showed no change in the crystal structure,which confirmed the high stability of CFGNZ.The density functional theory(DFT)based calculations show that the closeness of d(p)-band centers to the Fermi level(EF)plays a major role in determining active sites.This work highlights the tremendous potential of CFGNZ HEA for OER,which is the primary reaction involved in water splitting.展开更多
Low-grade high-sulfur bauxite was pretreated via suspension roasting and muffle furnace roasting to remove sulfur and enhance digestion properties.The results show that sulfur can be efficiently removed,and the alumin...Low-grade high-sulfur bauxite was pretreated via suspension roasting and muffle furnace roasting to remove sulfur and enhance digestion properties.The results show that sulfur can be efficiently removed,and the alumina digestion properties are significantly improved after suspension roasting.Under optimal conditions(t=70 min,T=280°C,w(CaO)=8%and Nk=245 g/L),the digestion ratios are 94.45%and 92.08%for the suspension-roasted and muffle-roasted ore,respectively,and the apparent activation energies are 63.26 and 64.24 kJ/mol,respectively.Two crystal models were established by Materials Studio based on the XRD patterns.The DFT simulation shows that the existing Al—O bands after suspension roasting can improve alumina digestion.The(104)and(113)planes of Al2O3 after suspension roasting are found to combine with NaOH more easily than those of Al2O3 treated in a muffle furnace.展开更多
CO2 gasification of Fuijian high-metamorphous anthracite with black liquor （BL） and/or mixture of BL and calcium stuff （BL＋Ca） as catalyst was studied by using a thermogravimetry under 750-950℃ at ambient pressu...CO2 gasification of Fuijian high-metamorphous anthracite with black liquor （BL） and/or mixture of BL and calcium stuff （BL＋Ca） as catalyst was studied by using a thermogravimetry under 750-950℃ at ambient pressure. When the coal was impregnated with an appropriate quantity of Ca and BL mixture, the catalytic activity of CO2 gasification was enhanced obviously. With a loading of 8%Na-BL＋2%Ca, the carbon conversion of three coal samples tested reaches up to 92.9%-99.3% at 950℃ within 30min. The continuous formation of alkali surface compounds such as （[-COM], [-CO2M]） and the presence of exchanged Ca, such as calcium phenolate and calcium carboxylates （COO）2Ca, contribute to the increase in catalytic efficiency, and using BL＋Ca is more efficient than that adding BL only, The homogeneous model and shrinking-core model were applied to correlate the data of conversion with time and to estimate the reaction rate constants under different temperature. The corresponding reaction activation energy （Ea） and pre-exponential factor of three anthracites were estimated. It is found that Ea is in the range from 73.6 to 121.4kJ·mol^-1 in the case of BL＋Ca, and 74.3 to 104.2kJ·mol^-1 when only BL was used as the catalyst, both of which are much less than that from 143.5 to 181.4kJ·mol^-1 if no catalyst used. It is clearly demonstrated that both of BL＋Ca mixture and BL could be the source of cheap and effective catalyst for coal gasification.展开更多
基金Supported by the National Natural Science Foundation of China （No.20476089） and the Project of the Ministry of Science and Technology of China （No.2004CCA05500）.
文摘The kinetics of non-catalyzed decompositions of xylose and its decomposition product furfural in high temperature liquid water （HTLW） was studied for temperature from 180 to 220℃ and under pressure of 10MPa. The main products of xylose decomposition were furfural and formic acid, and furfural further degraded to formic acid under HTLW condition. With the assumption of first order kinetics e.quation, the evaluated activation energy of xylose and furfural decomposition was 123.27kJ·mol^-1 and 58.84kJ·mol^-1, respectively.
基金supported by the National Natural Science Foundation of China (Nos. 51672064 and U1435206)
文摘Transition metal diborides based ultrahigh temperature ceramics(UHTCs) are characterized by high melting point, high strength and hardness, and high electrical and thermal conductivity. The high thermal conductivity arises from both electronic and phonon contributions. Thus electronic and phonon contributions must be controlled simultaneously in reducing the thermal conductivity of transition metal diborides. In high entropy(HE) materials, both electrons and phonons are scattered such that the thermal conductivity can significantly be reduced, which opens a new window to design novel insulating materials. Inspired by the high entropy effect, porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is designed in this work as a new thermal insulting ultrahigh temperature material and is synthesized by an in-situ thermal borocarbon reduction/partial sintering process. The porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 possesses high porosity of 75.67%, pore size of 0.3–1.2 μm, homogeneous microstructure with small grain size of 400–800 nm, which results in low room temperature thermal diffusivity and thermal conductivity of 0.74 mm2 s^-1 and 0.51 W m^-1K^-1, respectively. In addition, it exhibits high compressive strength of3.93 MPa. The combination of these properties indicates that exploring porous high entropy ceramics such as porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is a novel strategy in making UHTCs thermal insulating.
基金Project(2652014017) supported by the Fundamental Research Funds for the Central Universities,China
文摘The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.
基金Supported by the National Natural Science Foundation of China （20674068） and the Natural Science Foundation of Zhejiang Province （Y405157）.
文摘The decomposition kinetics of glucose was studied in high-temperature liquid water （HTLW） from 180 to 220℃ under a pressure of 10 MPa. It was found the main products from glucose decomposition were 5-hydroxymethylfurfural （5-HMF） and levulinic acid （LA）. The decomposition kinetics of 5-HMF and stability of LA in HTLW were further investigated. A kinetic model for glucose decomposition was proposed accordingly. In the model, a series of first-order reactions with the consideration of parallel by-reactions were used to illustrate the decomposition of glucose. The decomposition activation energies of glucose, 5-HMF, and LA were evaluated as 118.85, 95.40, and 31.29 kJ·mol^-1, respectively.
基金supported by the National Natural Science Foundation of China(No.21676300)the Shandong Provincial Natural Science Foundation(No.ZR2018MB035)+3 种基金the Fundamental Research Funds for the Central Universities(Nos.19CX02008A and 16CX06007A)PetroChina Innovation Foundation(No.2019D-5007-0401)Taishan Scholars Program of Shandong Province(No.tsqn201909065)Tsinghua University Initiative Scientific Research Program.
文摘Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.
基金supported by the 333 Projects of Jiangsu Province,China(Grant No.BRA2018045)the Industry-University Research Cooperation Project of Jiangsu Province,China(Grant No.BY2018194)+1 种基金Metasequoia Faculty Research Funding of Nanjing Forestry University(Grant No.163040160)support provided by the Australian Research Council Discovery Projects
文摘Advanced materials for electrocatalytic water splitting applications have been sought-after considering both environmental and economic requirements.However,the traditional materials design concept limits the exploration of high-performance catalysts.The born of a materials design concept based on multiple elements,high-entropy materials,provides a promising path to break the shackles of compositional design in materials science.A number of high-entropy materials were reported to show remarkable properties for electrocatalytic water splitting applications.High-entropy materials were widely confirmed to be one kind of the best electrocatalysts for water splitting applications.Due to the synergy of multiple metal components,they show excellent catalytic activity.Several nontraditional methods were developed and reported to prepare high-performance high-entropy materials.This review article presents the recent progress on high-entropy materials for electrocatalytic water splitting applications.Moreover,it presents the research interests and future prospects in this field.
基金The authors gratefully acknowledge the financial support of the project from the National Natural Science Foundation of China(51862026)the Natural Science Foundation of Jiangxi Province(20202ACBL214011,20192ACBL21048)the Aeronautical Science Foundation of China(2017ZF56027)。
文摘Developing efficient,stable and economical electrocatalyst for oxygen evolution reaction(OER)is a significant pathway to produce clean energy from water splitting.Herein,the promising and highly efficient porous CoCrFeNiMo high entropy alloys(HEAs)were prepared by microwave sintering using Mg space holder.Owing to unique properties of high entropy alloys and abundant active surface area,the porous CoCrFeNiMo-20 Mg exhibits excellent catalytic performance and prominent electrochemical stability with a low overpotential of 220 mV to reach current density of 10 mA cm^(-2),a small Tafel slope of 59.0 mV dec^(-1) and long-term durability for 24 h in 1.0 M KOH.The results of microstructure and element states indicate that crystal defects,porous structure and villous hydroxides are the reasons for high OER performance of the CoCrFeNiMo.This work not only provides a new way to prepare electrocatalysts,but also proves the important application of high entropy alloys in functional materials.
基金the Institute of Eminence(IoE)MHRD grant of the Indian Institute of Science.N.K.K.acknowledges the Newton Fellowship award from the Royal Society UK(NIF\R1\191571)the core research grant and Ramanujan Fellowship.C.S.T.acknowledges AOARD grant no.FA2386-19-1-4039.
文摘Oxygen evolution reaction(OER)is the key step involved both in water splitting devices and rechargeable metal-air batteries,and hence,there is an urgent need for a stable and low-cost material for efficient OER.In the present investigation,Co-Fe-Ga-NiZn(CFGNZ)high entropy alloy(HEA)has been utilized as a low-cost electrocatalyst for OER.Herein,after cyclic voltammetry activation,CFGNZ-nanoparticles(NPs)are covered with oxidized surface and form high entropy(oxy)hydroxides(HEOs),exhibiting a low overpotential of 370 mV to achieve a current density of 10 mA/cm^(2)with a small Tafel slope of 71 mV/dec.CFGNZ alloy has higher electrochemical stability in comparison to state-of-the art RuO2 electrocatalyst as no degradation has been observed up to 10 h of chronoamperometry.Transmission electron microscopy(TEM)studies after 10 h of long-term chronoamperometry test showed no change in the crystal structure,which confirmed the high stability of CFGNZ.The density functional theory(DFT)based calculations show that the closeness of d(p)-band centers to the Fermi level(EF)plays a major role in determining active sites.This work highlights the tremendous potential of CFGNZ HEA for OER,which is the primary reaction involved in water splitting.
基金Projects(U1812402,51774102,51574095,51664005)supported by the National Natural Science Foundation of ChinaProjects([2015]4005,[2017]5788,[2017]5626,KY(2015)334)supported by Talents of Guizhou Science and Technology Cooperation Platform,China。
文摘Low-grade high-sulfur bauxite was pretreated via suspension roasting and muffle furnace roasting to remove sulfur and enhance digestion properties.The results show that sulfur can be efficiently removed,and the alumina digestion properties are significantly improved after suspension roasting.Under optimal conditions(t=70 min,T=280°C,w(CaO)=8%and Nk=245 g/L),the digestion ratios are 94.45%and 92.08%for the suspension-roasted and muffle-roasted ore,respectively,and the apparent activation energies are 63.26 and 64.24 kJ/mol,respectively.Two crystal models were established by Materials Studio based on the XRD patterns.The DFT simulation shows that the existing Al—O bands after suspension roasting can improve alumina digestion.The(104)and(113)planes of Al2O3 after suspension roasting are found to combine with NaOH more easily than those of Al2O3 treated in a muffle furnace.
基金Supported by the National Natural Science Foundation of China （No.20376014） and Fujian Science and Technology Council Grant （HG99-01）.
文摘CO2 gasification of Fuijian high-metamorphous anthracite with black liquor （BL） and/or mixture of BL and calcium stuff （BL＋Ca） as catalyst was studied by using a thermogravimetry under 750-950℃ at ambient pressure. When the coal was impregnated with an appropriate quantity of Ca and BL mixture, the catalytic activity of CO2 gasification was enhanced obviously. With a loading of 8%Na-BL＋2%Ca, the carbon conversion of three coal samples tested reaches up to 92.9%-99.3% at 950℃ within 30min. The continuous formation of alkali surface compounds such as （[-COM], [-CO2M]） and the presence of exchanged Ca, such as calcium phenolate and calcium carboxylates （COO）2Ca, contribute to the increase in catalytic efficiency, and using BL＋Ca is more efficient than that adding BL only, The homogeneous model and shrinking-core model were applied to correlate the data of conversion with time and to estimate the reaction rate constants under different temperature. The corresponding reaction activation energy （Ea） and pre-exponential factor of three anthracites were estimated. It is found that Ea is in the range from 73.6 to 121.4kJ·mol^-1 in the case of BL＋Ca, and 74.3 to 104.2kJ·mol^-1 when only BL was used as the catalyst, both of which are much less than that from 143.5 to 181.4kJ·mol^-1 if no catalyst used. It is clearly demonstrated that both of BL＋Ca mixture and BL could be the source of cheap and effective catalyst for coal gasification.
