The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were...The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.展开更多
Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg3Al1-xFex,containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective ...Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg3Al1-xFex,containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg3Al)to 1(Ir/Mg3Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg3Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg3Al1–xFex support to the dispersed Ir particles and the surface geometry.展开更多
The electrocatalytic N_(2)reduction reaction(NRR)is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions.The activity and selectivity of electrochemical NRR are rest...The electrocatalytic N_(2)reduction reaction(NRR)is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions.The activity and selectivity of electrochemical NRR are restricted to a strong polarized electric field induced by the catalyst,correct electron transfer direction,and electron tunneling distance between bare electrode and active sites.By coupling the chemical vapor deposition method with the poly(methyl methacylate)-transfer method,an ultrathin sandwich catalyst,i.e.,Fe atoms(polarized electric field layer)sandwiched between ultrathin(within electron tunneling distance)BN(catalyst layer)and graphene film(conducting layer),is fabricated for electrocatalytic NRR.The sandwich catalyst not only controls the transfer of electrons to the BN surface in the correct direction under applied voltage but also suppresses hydrogen evolution reaction by constructing a neutral polarization electric field without metal exposure.The sandwich electrocatalyst NRR system achieve NH3 yield of 8.9μg h^(−1)cm^(−2)and Faradaic Efficiency of 21.7%.The N_(2)adsorption,activation,and polarization electric field changes of three sandwich catalysts(BN-Fe-G,BN-Fe-BN,and G-Fe-G)during the electrocatalytic NRR are investigated by experiments and density functional theory simulations.Driven by applied voltage,the neutral polarized electric field induced by BN-Fe-G leads to the high activity of electrocatalytic NRR.展开更多
Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity i...Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries.However,post-treatments (acid washing,second pyrolysis,and so on) are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe^(3+) sources (anhydrous Fe Cl_(3)) into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_(x) active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn^(2+)),synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn^(2+)) precursor which was obtained by adding the anhydrous Fe Cl_(3)source into the Zn(NO_(3))_(2)·6H_(2)O/methanol solution before mixing,possessed the highest Fe-N_(x)active sites due to the high-efficiency substitution of Zn^(2+)ions with Fe^(3+) ions during ZIF-8 growth,the strong interaction between Fe^(3+) ions and N atoms of 2-Methylimidazole (2-MIm),and ZIF-8’s micropore confinement effect.As a result,Fe-NC(Zn^(2+)) presented high ORR activity in the entire p H range (p H=1,7,and 13).At p H=13,Fe-NC(Zn^(2+)) exhibited a half-wave potential (E1/2) of 0.95 V (vs.reversible hydrogen electrode),which was 70 m V higher than that of commercial Pt/C.More importantly,Fe-NC(Zn^(2+)) showed superior ORR stability in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V) was obtained when Fe-NC(Zn^(2+)) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn^(2+)) has enormous potential for use in flexible and wearable Mg-air batteries.展开更多
The effect of Fe-doping on the magnetic properties of the ABO3-type perovskite cobaltites La0.7Ba0.3CoO3（0≤ y≤0.80） is reported. With no apparent structural change in any doped sample, the Curie temperature （Tc）...The effect of Fe-doping on the magnetic properties of the ABO3-type perovskite cobaltites La0.7Ba0.3CoO3（0≤ y≤0.80） is reported. With no apparent structural change in any doped sample, the Curie temperature （Tc） and the magnetization （M） are greatly suppressed for y ≤0.30 samples, while a distinct increase in Tc for the y=0.40 sample is observed. With the further increase of Fe concentration, Tc increases monotonically. Griffiths-like phases in 0.40≤y ≤0.60 samples are confirmed. The formation of the Griffiths-like phase is ascribed to B-site disordering induced isolation of ferromagnetic （FM） clusters above Tc.展开更多
The large single-crystal diamond with FeS doping along the （111） face is synthesized from the FeNi-C system by the temperature gradient method （TGM） under high-pressure and high-temperature （HPHT）. the effects o...The large single-crystal diamond with FeS doping along the （111） face is synthesized from the FeNi-C system by the temperature gradient method （TGM） under high-pressure and high-temperature （HPHT）. the effects of different FeS additive content on the shape, color, and quality of diamond are investigated. It is found that the （111） face of diamond is dominated and the （100） face of diamond disappears gradually with the increase of the FeS content. At the same time, the color of the diamond crystal changes from light yellow to gray-green and even gray-yellow. The stripes and pits corrosion on the diamond surface are observed to turn worse. The effects of FeS doping on the shape and surface morphology of diamond crystal are explained by the number of hang bonds in different surfaces of diamond. It can be shown from the test results of the Fourier transform infrared （FTIR） spectrum that there exists an S element in the obtained diamond. The N element content values in different additive amounts of diamond are calculated. The XPS spectrum results demonstrate that our obtained diamond contains S elements that exist in S-C and S-C-O forms in a diamond lattice. This work contributes to the further understanding and research of FeS-doped large single-crystal diamond characterization.展开更多
The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 （KNN） crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. T...The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 （KNN） crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The full potentiallinearized augumented plane wave plus local orbitals （APW-LO） method and the supercell method are used in the calculation for the KNN crystal with and without the La doping. The results show that the piezoelectricity originates from the strong hybridization between the Nb atom and the O atom, and the substitution of the K or Na atom by the La impurity atom introduces the anisotropic relaxation and enhances the piezoelectricity at first and then restrains the hybridization of the Nb-O atoms when the La doping content further increases.展开更多
TiO2 thin films non-uniformly doped by La^3＋ were prepared by sol-gel method. The comparison of thin film activities, which was characterized by photocatalytic degradation of methyl orange, shows that doping modes ha...TiO2 thin films non-uniformly doped by La^3＋ were prepared by sol-gel method. The comparison of thin film activities, which was characterized by photocatalytic degradation of methyl orange, shows that doping modes have great activities. The non-uniformly effects on photocatalytic doped TiO2 films resuh in good photocatalytic activities with an optimal concentration; about 0. 5% （ atom fraction ）. UV-Vis transmittance spectra indicate that the absorption edges of these TiO2 thin films shift to ward longer wave- lengths remarkably, and electrochemical behavior also reveales that e^- -h^＋ pairs are prone to formation and separation under UV irradiation. The mechanism of photocatalytic activities are enhanced by La^3＋ non-uniformly doping was discussed on the analogy of the theory of “window effect” of solar cell heterojunction.展开更多
基金the Foundation of Wuhan University of Science and Technology
文摘The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.
基金the National Natural Science Foundation of China，the Program for New Century Excellent Talents in University，the National Science Foundation Project of CQ CSTC，the Fundamental Research Funds for the Central Universities
文摘Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg3Al1-xFex,containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg3Al)to 1(Ir/Mg3Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg3Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg3Al1–xFex support to the dispersed Ir particles and the surface geometry.
文摘The electrocatalytic N_(2)reduction reaction(NRR)is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions.The activity and selectivity of electrochemical NRR are restricted to a strong polarized electric field induced by the catalyst,correct electron transfer direction,and electron tunneling distance between bare electrode and active sites.By coupling the chemical vapor deposition method with the poly(methyl methacylate)-transfer method,an ultrathin sandwich catalyst,i.e.,Fe atoms(polarized electric field layer)sandwiched between ultrathin(within electron tunneling distance)BN(catalyst layer)and graphene film(conducting layer),is fabricated for electrocatalytic NRR.The sandwich catalyst not only controls the transfer of electrons to the BN surface in the correct direction under applied voltage but also suppresses hydrogen evolution reaction by constructing a neutral polarization electric field without metal exposure.The sandwich electrocatalyst NRR system achieve NH3 yield of 8.9μg h^(−1)cm^(−2)and Faradaic Efficiency of 21.7%.The N_(2)adsorption,activation,and polarization electric field changes of three sandwich catalysts(BN-Fe-G,BN-Fe-BN,and G-Fe-G)during the electrocatalytic NRR are investigated by experiments and density functional theory simulations.Driven by applied voltage,the neutral polarized electric field induced by BN-Fe-G leads to the high activity of electrocatalytic NRR.
基金supported by the National Natural Science Foundation of China(22171266)the FJIRSM&IUE Joint Research Fund(RHZX-2019-002)+2 种基金the STS Project(KFJ-STS-QYZD-2021-09002)the National Key Basic Research Program of China(2017YFA0403402)the Project of the National Natural Science Foundation of China(U1932119)。
文摘Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries.However,post-treatments (acid washing,second pyrolysis,and so on) are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe^(3+) sources (anhydrous Fe Cl_(3)) into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_(x) active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn^(2+)),synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn^(2+)) precursor which was obtained by adding the anhydrous Fe Cl_(3)source into the Zn(NO_(3))_(2)·6H_(2)O/methanol solution before mixing,possessed the highest Fe-N_(x)active sites due to the high-efficiency substitution of Zn^(2+)ions with Fe^(3+) ions during ZIF-8 growth,the strong interaction between Fe^(3+) ions and N atoms of 2-Methylimidazole (2-MIm),and ZIF-8’s micropore confinement effect.As a result,Fe-NC(Zn^(2+)) presented high ORR activity in the entire p H range (p H=1,7,and 13).At p H=13,Fe-NC(Zn^(2+)) exhibited a half-wave potential (E1/2) of 0.95 V (vs.reversible hydrogen electrode),which was 70 m V higher than that of commercial Pt/C.More importantly,Fe-NC(Zn^(2+)) showed superior ORR stability in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V) was obtained when Fe-NC(Zn^(2+)) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn^(2+)) has enormous potential for use in flexible and wearable Mg-air batteries.
基金Project supported by the National Basic Research Program of China (Grant No 2009CB929201)the National Natural Science Foundation of China (Grant No 10774179)
文摘The effect of Fe-doping on the magnetic properties of the ABO3-type perovskite cobaltites La0.7Ba0.3CoO3（0≤ y≤0.80） is reported. With no apparent structural change in any doped sample, the Curie temperature （Tc） and the magnetization （M） are greatly suppressed for y ≤0.30 samples, while a distinct increase in Tc for the y=0.40 sample is observed. With the further increase of Fe concentration, Tc increases monotonically. Griffiths-like phases in 0.40≤y ≤0.60 samples are confirmed. The formation of the Griffiths-like phase is ascribed to B-site disordering induced isolation of ferromagnetic （FM） clusters above Tc.
基金Project supported by the National Natural Science Foundation of China(Grant No.51772120)the Project for Key Science and Technology Research of Henan Province,China(Grant Nos.162102210275 and 172102210283)+1 种基金the Key Scientific Research Project in Colleges and Universities of Henan Province,China(Grant Nos.18A430017 and 17A430020)the Professional Practice Demonstration Base for Professional Degree Graduate in Material Engineering of Henan Polytechnic University,China(Grant No.2016YJD03)
文摘The large single-crystal diamond with FeS doping along the （111） face is synthesized from the FeNi-C system by the temperature gradient method （TGM） under high-pressure and high-temperature （HPHT）. the effects of different FeS additive content on the shape, color, and quality of diamond are investigated. It is found that the （111） face of diamond is dominated and the （100） face of diamond disappears gradually with the increase of the FeS content. At the same time, the color of the diamond crystal changes from light yellow to gray-green and even gray-yellow. The stripes and pits corrosion on the diamond surface are observed to turn worse. The effects of FeS doping on the shape and surface morphology of diamond crystal are explained by the number of hang bonds in different surfaces of diamond. It can be shown from the test results of the Fourier transform infrared （FTIR） spectrum that there exists an S element in the obtained diamond. The N element content values in different additive amounts of diamond are calculated. The XPS spectrum results demonstrate that our obtained diamond contains S elements that exist in S-C and S-C-O forms in a diamond lattice. This work contributes to the further understanding and research of FeS-doped large single-crystal diamond characterization.
基金supported by National Nature Science Foundation of China (No.11075110)
文摘The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 （KNN） crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The full potentiallinearized augumented plane wave plus local orbitals （APW-LO） method and the supercell method are used in the calculation for the KNN crystal with and without the La doping. The results show that the piezoelectricity originates from the strong hybridization between the Nb atom and the O atom, and the substitution of the K or Na atom by the La impurity atom introduces the anisotropic relaxation and enhances the piezoelectricity at first and then restrains the hybridization of the Nb-O atoms when the La doping content further increases.
文摘TiO2 thin films non-uniformly doped by La^3＋ were prepared by sol-gel method. The comparison of thin film activities, which was characterized by photocatalytic degradation of methyl orange, shows that doping modes have great activities. The non-uniformly effects on photocatalytic doped TiO2 films resuh in good photocatalytic activities with an optimal concentration; about 0. 5% （ atom fraction ）. UV-Vis transmittance spectra indicate that the absorption edges of these TiO2 thin films shift to ward longer wave- lengths remarkably, and electrochemical behavior also reveales that e^- -h^＋ pairs are prone to formation and separation under UV irradiation. The mechanism of photocatalytic activities are enhanced by La^3＋ non-uniformly doping was discussed on the analogy of the theory of “window effect” of solar cell heterojunction.
