The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2) reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into...The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2) reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N_(4)-C)configuration to obtain Ni-X-N_(3)-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N_(3)-C(X:S,Se,and Te)SACs,Ni-Se-N_(3)-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98% at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2) battery integrated with Ni-Se-N_(3)-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm^(-2) and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N_(4)-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N_(3)-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of ^(*)COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.展开更多
采用铝液通氢的方法模拟木条裂解产物氢、H2O（汽）与铝液作用过程,利用化学分析、氢分析、扫描电子显微镜（SEM）以及分子动力学方法,研究了氢及通氢时带入的水与铝液反应过程,模拟计算氢在铝液中的扩散方式以及影响扩散的关键环节。...采用铝液通氢的方法模拟木条裂解产物氢、H2O（汽）与铝液作用过程,利用化学分析、氢分析、扫描电子显微镜（SEM）以及分子动力学方法,研究了氢及通氢时带入的水与铝液反应过程,模拟计算氢在铝液中的扩散方式以及影响扩散的关键环节。研究氢、氧化铝夹杂在铝样中的形貌与分布规律,从微观机制上揭示氢对电解铝液的传质规律。结果表明:熄效应使铝液氢含量增加,实验铝液氢含量达到1.266 m L/100 g,铝液中的Al3Ti、Al2O3共同吸附铝液中的氢形成AlTiOH团簇,寄生于氧化铝夹杂表面的氢随氧化铝夹杂悬浮于铝液中,是铝液中氢含量明显升高的原因。展开更多
Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that...Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.展开更多
Preparation of porous Ti Al-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti-43 Al-9V-1Y powder(D50=50 μm), carboxymethyl cellulose, and guar gum were used to p...Preparation of porous Ti Al-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti-43 Al-9V-1Y powder(D50=50 μm), carboxymethyl cellulose, and guar gum were used to prepare the aqueous-based slurries for freeze-casting. Results showed that the porous Ti Al was obtained by using a freezing temperature of -5 ℃ and the pore structure was tailored by varying the particle content of slurry. The total porosity reduced from 81% to 62% and the aligned pore width dropped from approximately 500 to around 270 μm, with increasing the particle content from 10 to 30 vol.%. Furthermore, the compressive strength along the aligned pores increased from 16 to 120 MPa with the reduction of porosity. The effective thermal conductivities of porous Ti Al were lower than 1.81 W/(m·K) and showed anisotropic property with respect to the pore orientation.展开更多
采用高温电阻炉制备了两组Cu-43%Zn合金,利用蒸馏法、X射线衍射(XRD)、化学分析方法研究了在氮气和空气气氛下的熔炼过程中,Cu-Zn合金的质量损失与物相转变规律及低熔点合金组元Zn的蒸发、汽化过程。并采用差示扫描量热-热重分析连用(DS...采用高温电阻炉制备了两组Cu-43%Zn合金,利用蒸馏法、X射线衍射(XRD)、化学分析方法研究了在氮气和空气气氛下的熔炼过程中,Cu-Zn合金的质量损失与物相转变规律及低熔点合金组元Zn的蒸发、汽化过程。并采用差示扫描量热-热重分析连用(DSC-TGA)方法考察了该合金在氮气和空气气氛下升温状态的蒸发、氧化、汽化、造渣行为。通过采用蒸馏法和化学分析方法测量样品和基体Zn含量的质量损失随时间和温度的变化曲线,得出:试样质量和合金基体Zn含量均随着蒸发温度的升高和时间的延长而降低;在温度一定的条件下,试样质量和基体Zn含量降低到一定值时,保持相对恒定;温度越高,试样质量和Zn含量剩余越少。DSC-TGA的实验结果结合kissinger,Flynn-WallOzawa方程得出:在氮气和空气气氛下Cu-Zn合金汽化峰的表观激活能依次为:5815.28,5107.05 k J·mol^(-1)。展开更多
文摘The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2) reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N_(4)-C)configuration to obtain Ni-X-N_(3)-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N_(3)-C(X:S,Se,and Te)SACs,Ni-Se-N_(3)-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98% at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2) battery integrated with Ni-Se-N_(3)-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm^(-2) and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N_(4)-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N_(3)-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of ^(*)COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.
文摘采用铝液通氢的方法模拟木条裂解产物氢、H2O（汽）与铝液作用过程,利用化学分析、氢分析、扫描电子显微镜（SEM）以及分子动力学方法,研究了氢及通氢时带入的水与铝液反应过程,模拟计算氢在铝液中的扩散方式以及影响扩散的关键环节。研究氢、氧化铝夹杂在铝样中的形貌与分布规律,从微观机制上揭示氢对电解铝液的传质规律。结果表明:熄效应使铝液氢含量增加,实验铝液氢含量达到1.266 m L/100 g,铝液中的Al3Ti、Al2O3共同吸附铝液中的氢形成AlTiOH团簇,寄生于氧化铝夹杂表面的氢随氧化铝夹杂悬浮于铝液中,是铝液中氢含量明显升高的原因。
基金financially supported by the National Key R&D Program of China (2016YFC0204201)the National Natural Science Foundation of China (21677114, 21477095, 21876139)the Fundamental Research Funds for the Central Universities (xjj2017170)~~
文摘Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.
基金Projects(51775418,51375372)supported by the National Natural Science Foundation of China
文摘Preparation of porous Ti Al-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti-43 Al-9V-1Y powder(D50=50 μm), carboxymethyl cellulose, and guar gum were used to prepare the aqueous-based slurries for freeze-casting. Results showed that the porous Ti Al was obtained by using a freezing temperature of -5 ℃ and the pore structure was tailored by varying the particle content of slurry. The total porosity reduced from 81% to 62% and the aligned pore width dropped from approximately 500 to around 270 μm, with increasing the particle content from 10 to 30 vol.%. Furthermore, the compressive strength along the aligned pores increased from 16 to 120 MPa with the reduction of porosity. The effective thermal conductivities of porous Ti Al were lower than 1.81 W/(m·K) and showed anisotropic property with respect to the pore orientation.
文摘采用高温电阻炉制备了两组Cu-43%Zn合金,利用蒸馏法、X射线衍射(XRD)、化学分析方法研究了在氮气和空气气氛下的熔炼过程中,Cu-Zn合金的质量损失与物相转变规律及低熔点合金组元Zn的蒸发、汽化过程。并采用差示扫描量热-热重分析连用(DSC-TGA)方法考察了该合金在氮气和空气气氛下升温状态的蒸发、氧化、汽化、造渣行为。通过采用蒸馏法和化学分析方法测量样品和基体Zn含量的质量损失随时间和温度的变化曲线,得出:试样质量和合金基体Zn含量均随着蒸发温度的升高和时间的延长而降低;在温度一定的条件下,试样质量和基体Zn含量降低到一定值时,保持相对恒定;温度越高,试样质量和Zn含量剩余越少。DSC-TGA的实验结果结合kissinger,Flynn-WallOzawa方程得出:在氮气和空气气氛下Cu-Zn合金汽化峰的表观激活能依次为:5815.28,5107.05 k J·mol^(-1)。
