As a noble metal substitute,two-dimensional(2D)hierarchical nano-frame structures have attracted great interest as candidate catalysts due to their remarkable advantages-high intrinsic activity,high electron mobility,...As a noble metal substitute,two-dimensional(2D)hierarchical nano-frame structures have attracted great interest as candidate catalysts due to their remarkable advantages-high intrinsic activity,high electron mobility,and straightforward surface functionalization.Therefore,they may replace Pt-based catalysts in oxygen reduction reaction(ORR)applications.Herein,a simple method is developed to design hierarchical nano-frame structures assembled via 2D NiO and N-doped graphene(NG)nanosheets.This procedure can yield nanostructures that satisfy the criteria correlated with improved electrocatalytic performance,such as large surface area,numerous undercoordinated atoms,and high defect densities.Further,porous NG nanosheet architectures,featuring NiO nanosheets densely coordinated with accessible holey Fe_(2)O_(3) moieties,can enhance mesoporosity and balance hydrophilicity.Such improvements can facilitate charge transport and expose formerly inaccessible reaction sites,maximizing active site density utilization.Density functional theory(DFT)calculations reveal favored O_(2) adsorption and dissociation on Fe_(2)O_(3) hybrid structures when supported by 2D NiO and NG nanomaterials,given 2D materials donated charge to Fe_(2)O_(3) active sites.Our systematic studies reveal that synergistic contributions are responsible for enriching the catalytic activity of Fe_(2)O_(3)@NiO/NG in alkaline media-encompassing internal voids and pores,unique hierarchical support structures,and concentrated N-dopant and bimetallic atomic interactions.Ultimately,this work expands the toolbox for designing and synthesizing highly efficient 2D/2D shelled functional nanomaterials with transition metals,endeavoring to benefit energy conversion and related ORR applications.展开更多
Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-ind...Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-index faceted iron oxide(Fe_(2)O_(3))nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts,effectively improving the electrochemical performance of Li-S batteries.The theoretical and experimental results all indicate that high-index Fe_(2)O_(3)crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li_(2)S.The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g^(-1)at 0.1 C and excellent cycling performance with a low capacity fading of 0.025%per cycle during 1600 cycles at 2 C.Even with a high sulfur loading of 9.41 mg cm^(-2),a remarkable areal capacity of 7.61 mAh cm^(-2)was maintained after 85 cycles.This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering,deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry,affording a novel perspective for the design of advanced sulfur electrodes.展开更多
The oxidative dehydrogenation (ODH) of isobutane over Cr_2O_3/La_2(CO_3)_3 has been investigated in a low-pressure Knudsen cell reactor, under conditions where the kinetics of the primary reaction steps can be accurat...The oxidative dehydrogenation (ODH) of isobutane over Cr_2O_3/La_2(CO_3)_3 has been investigated in a low-pressure Knudsen cell reactor, under conditions where the kinetics of the primary reaction steps can be accurately determined. By heating the catalyst at a constant rate from 150-300℃, temperature fluctuations due to non-equilibrium adsorption are minimized. The evolved gas profiles show that ODH to isobutene and water is a primary reaction pathway, while carbon dioxide, which forms from the catalyst during reaction, is the only other product. This CO2 evolution may enhance the activity of the catalyst. Isobutene formation proceeds with the participation of lattice oxygen from the Cr2O3/La2(CO3)3 catalyst. The intrinsic Arrhenius rate constant for the ODH of isobutane isk(s-1) = 1011.5±2.2exp{-((55±5) -ΔHads kJmol-1)/RT}The small pre-exponential factor is expected for a concerted mechanism and for such a catalyst with a small surface area and limited porosity.展开更多
The effect of Cr2O3 on the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specro...The effect of Cr2O3 on the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specrometer) and so on. Computer pattern recognition is applied to optimize the heat-treatment schedules. The experimental results show that the base glass containing more than 1 .5 % (mass fraction) Cr2O3 can be nucleated internally and converted to spheroidal crystal glass materials. The spheroidal crystal consisted of fibrous wollastonite crystals radiating from a center. The residual glass phase filled in the interstices between the fibers and between the spherulites. During heat treatment process, the valence states ofchromium changed from Cr6- to Cr3-, and the Cr-spinel solidsolution [CaCr2O4] precipitated followed this valence change. At the primary stage of crystallization, the Cr-spinel could act as a nucleating center on which the principal or}stalline phase β-CaSiO3 grew epitaxially.展开更多
铬氧化物材料(Cr8O21)用作锂一次电池正极材料时放电倍率性能较差。利用高温固相法以Al_(2)O_(3)、TiO_(2)对Cr8O_(21)进行包覆改性,通过金属氧化物间的协同作用提升了Cr_(8)O_(21)的倍率性能。X射线衍射(XRD)结果显示包覆Al_(2)O_(3)、...铬氧化物材料(Cr8O21)用作锂一次电池正极材料时放电倍率性能较差。利用高温固相法以Al_(2)O_(3)、TiO_(2)对Cr8O_(21)进行包覆改性,通过金属氧化物间的协同作用提升了Cr_(8)O_(21)的倍率性能。X射线衍射(XRD)结果显示包覆Al_(2)O_(3)、TiO_(2)不会改变Cr_(8)O_(21)的晶体结构;扫描电子显微镜(SEM)、能量散射光谱(EDS)结果表明Al2O3和Ti O2都均匀包覆在Cr_(8)O_(21)表面。Cr_(8)O_(21)/Al_(2)O_(3)复合材料以质量比50∶1复合时放电性能最佳,比容量为342 m Ah/g (0.05 m A/cm^(2))、291 m Ah/g(1.0 m A/cm^(2)),容量保持率85%;Cr_(8)O_(21)/TiO_(2)复合材料以质量比100∶1复合时放电性能最佳,比容量为362 m Ah/g(0.05 m A/cm^(2))、303 m Ah/g (1.0 m A/cm^(2)),容量保持率83.75%。在大电流密度下无电压低头现象,容量保持率皆高于Cr8O21的容量保持率(75%)。展开更多
Cr_(2)O_(3)-bearing castables bonded with reactive MgO(RM)or calcium aluminate cement(CAC)were studied to evaluate the binder effect on their performance in corrosive environments.The properties of the as-prepared cas...Cr_(2)O_(3)-bearing castables bonded with reactive MgO(RM)or calcium aluminate cement(CAC)were studied to evaluate the binder effect on their performance in corrosive environments.The properties of the as-prepared castables were compared with respect to the differences in phase composition and microstructure.The corrosion behavior of the as-prepared castables by CaO-Al_(2)O_(3)-Fe_(2)O_(3)-SiO_(2)-based slag was systematically compared viarefractory cup testing at 1600℃with respect to the differences in phase composition and microstructure.The analysis indicates that RM bonded castables show higher apparent porosity,lower bulk density and strengths after drying at 110℃and firing at 1300℃,and higher permanent linear change after firing at 1300℃,but better slag corrosion and infiltration resistance compared with CAC bonded castables.展开更多
基金supported by the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(MSIT)(RS2023-00235596)and ERC Center(2022R1A5A1033719)。
文摘As a noble metal substitute,two-dimensional(2D)hierarchical nano-frame structures have attracted great interest as candidate catalysts due to their remarkable advantages-high intrinsic activity,high electron mobility,and straightforward surface functionalization.Therefore,they may replace Pt-based catalysts in oxygen reduction reaction(ORR)applications.Herein,a simple method is developed to design hierarchical nano-frame structures assembled via 2D NiO and N-doped graphene(NG)nanosheets.This procedure can yield nanostructures that satisfy the criteria correlated with improved electrocatalytic performance,such as large surface area,numerous undercoordinated atoms,and high defect densities.Further,porous NG nanosheet architectures,featuring NiO nanosheets densely coordinated with accessible holey Fe_(2)O_(3) moieties,can enhance mesoporosity and balance hydrophilicity.Such improvements can facilitate charge transport and expose formerly inaccessible reaction sites,maximizing active site density utilization.Density functional theory(DFT)calculations reveal favored O_(2) adsorption and dissociation on Fe_(2)O_(3) hybrid structures when supported by 2D NiO and NG nanomaterials,given 2D materials donated charge to Fe_(2)O_(3) active sites.Our systematic studies reveal that synergistic contributions are responsible for enriching the catalytic activity of Fe_(2)O_(3)@NiO/NG in alkaline media-encompassing internal voids and pores,unique hierarchical support structures,and concentrated N-dopant and bimetallic atomic interactions.Ultimately,this work expands the toolbox for designing and synthesizing highly efficient 2D/2D shelled functional nanomaterials with transition metals,endeavoring to benefit energy conversion and related ORR applications.
基金supported by the Natural Science Foundation of Zhejiang Province,China(Y4100001)Science Technology Planning Project ofZhejiang Province,China(2009F70004,2009R50020-6)~~
基金This work was supported by the National Natural Science Foundation of China(No.22078078)the Natural Science Foundation of Heilongjiang Province(No.LH2020B008)the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.2019DX13).
文摘Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-index faceted iron oxide(Fe_(2)O_(3))nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts,effectively improving the electrochemical performance of Li-S batteries.The theoretical and experimental results all indicate that high-index Fe_(2)O_(3)crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li_(2)S.The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g^(-1)at 0.1 C and excellent cycling performance with a low capacity fading of 0.025%per cycle during 1600 cycles at 2 C.Even with a high sulfur loading of 9.41 mg cm^(-2),a remarkable areal capacity of 7.61 mAh cm^(-2)was maintained after 85 cycles.This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering,deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry,affording a novel perspective for the design of advanced sulfur electrodes.
文摘The oxidative dehydrogenation (ODH) of isobutane over Cr_2O_3/La_2(CO_3)_3 has been investigated in a low-pressure Knudsen cell reactor, under conditions where the kinetics of the primary reaction steps can be accurately determined. By heating the catalyst at a constant rate from 150-300℃, temperature fluctuations due to non-equilibrium adsorption are minimized. The evolved gas profiles show that ODH to isobutene and water is a primary reaction pathway, while carbon dioxide, which forms from the catalyst during reaction, is the only other product. This CO2 evolution may enhance the activity of the catalyst. Isobutene formation proceeds with the participation of lattice oxygen from the Cr2O3/La2(CO3)3 catalyst. The intrinsic Arrhenius rate constant for the ODH of isobutane isk(s-1) = 1011.5±2.2exp{-((55±5) -ΔHads kJmol-1)/RT}The small pre-exponential factor is expected for a concerted mechanism and for such a catalyst with a small surface area and limited porosity.
文摘The effect of Cr2O3 on the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specrometer) and so on. Computer pattern recognition is applied to optimize the heat-treatment schedules. The experimental results show that the base glass containing more than 1 .5 % (mass fraction) Cr2O3 can be nucleated internally and converted to spheroidal crystal glass materials. The spheroidal crystal consisted of fibrous wollastonite crystals radiating from a center. The residual glass phase filled in the interstices between the fibers and between the spherulites. During heat treatment process, the valence states ofchromium changed from Cr6- to Cr3-, and the Cr-spinel solidsolution [CaCr2O4] precipitated followed this valence change. At the primary stage of crystallization, the Cr-spinel could act as a nucleating center on which the principal or}stalline phase β-CaSiO3 grew epitaxially.
文摘铬氧化物材料(Cr8O21)用作锂一次电池正极材料时放电倍率性能较差。利用高温固相法以Al_(2)O_(3)、TiO_(2)对Cr8O_(21)进行包覆改性,通过金属氧化物间的协同作用提升了Cr_(8)O_(21)的倍率性能。X射线衍射(XRD)结果显示包覆Al_(2)O_(3)、TiO_(2)不会改变Cr_(8)O_(21)的晶体结构;扫描电子显微镜(SEM)、能量散射光谱(EDS)结果表明Al2O3和Ti O2都均匀包覆在Cr_(8)O_(21)表面。Cr_(8)O_(21)/Al_(2)O_(3)复合材料以质量比50∶1复合时放电性能最佳,比容量为342 m Ah/g (0.05 m A/cm^(2))、291 m Ah/g(1.0 m A/cm^(2)),容量保持率85%;Cr_(8)O_(21)/TiO_(2)复合材料以质量比100∶1复合时放电性能最佳,比容量为362 m Ah/g(0.05 m A/cm^(2))、303 m Ah/g (1.0 m A/cm^(2)),容量保持率83.75%。在大电流密度下无电压低头现象,容量保持率皆高于Cr8O21的容量保持率(75%)。
基金Supported by Natural Science Foundation of Jilin Province(20220101024JC,20200201247JC,20170520110JH)National Natural Science Foundation of China(11504029,11474035)。
基金the Joint Founds of R&D Program of Henan Province (222301420034)National Natural Science Foundation of China (51802287)Collaborative Innovation Major Special Project of Zhengzhou (No. 20XTZX12025) for the financial support
文摘Cr_(2)O_(3)-bearing castables bonded with reactive MgO(RM)or calcium aluminate cement(CAC)were studied to evaluate the binder effect on their performance in corrosive environments.The properties of the as-prepared castables were compared with respect to the differences in phase composition and microstructure.The corrosion behavior of the as-prepared castables by CaO-Al_(2)O_(3)-Fe_(2)O_(3)-SiO_(2)-based slag was systematically compared viarefractory cup testing at 1600℃with respect to the differences in phase composition and microstructure.The analysis indicates that RM bonded castables show higher apparent porosity,lower bulk density and strengths after drying at 110℃and firing at 1300℃,and higher permanent linear change after firing at 1300℃,but better slag corrosion and infiltration resistance compared with CAC bonded castables.
