制备具有氧还原(ORR)与氧释放(OER)双功能催化活性的特殊孔道结构电催化剂是锂氧电池研究的挑战之一。本文以氧化石墨烯、硝酸铁、硝酸镧、柠檬酸为原料,结合溶胶凝胶和水热合成方法,制备出还原氧化石墨烯(RGO)与铁酸镧(LaFeO_3)复合的...制备具有氧还原(ORR)与氧释放(OER)双功能催化活性的特殊孔道结构电催化剂是锂氧电池研究的挑战之一。本文以氧化石墨烯、硝酸铁、硝酸镧、柠檬酸为原料,结合溶胶凝胶和水热合成方法,制备出还原氧化石墨烯(RGO)与铁酸镧(LaFeO_3)复合的双功能催化剂(RGO-LaFeO_3)。X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和Raman光谱分析结果确认该复合催化剂由纯相钙钛矿结构LaFeO_3和还原氧化石墨烯组成,扫描电子显微镜(SEM)观察到LaFeO_3纳米颗粒均匀地负载在RGO片层表面。锂氧电池测试结果指出,相对于LaFeO_3纳米粒子(NP-LaFeO_3),RGO-LaFeO_3催化剂具有更好的ORR和OER催化活性,归因于RGO特殊的三维导电多孔结构与LaFeO_3纳米粒子的协同催化作用。以RGO-LaFeO_3作为阴极催化剂的锂氧电池在限1000 m Ah?g^(-1)比容量、100 m A?g^(-1)电流密度条件下,可实现36周稳定的充放电循环,展示出良好的应用前景。展开更多
We reported the effects of annealing temperatures on microstructure and electrochemical properties of perovskite-type oxide LaFeO3 prepared by stearic acid combustion method. X-Ray diffraction（XRD） patterns show tha...We reported the effects of annealing temperatures on microstructure and electrochemical properties of perovskite-type oxide LaFeO3 prepared by stearic acid combustion method. X-Ray diffraction（XRD） patterns show that the annealed LaFeO3 powder has orthorhombic structure. Scanning electron microscopy（SEM） and transmission electron microscopy（TEM） images show the presence of homogeneously dispersed, less aggregated, and small crystals（30--40 nm） at annealing temperatures of 500 and 600 ℃. However, as the annealing temperature was increased to 700 and 800 ℃, the crystals began to combine with each other and grew into further larger crystals（90--100 nm）. The electrochemical performance of the annealed oxides was measured at 60 ℃ using chronopotentiometry, potentiodynamic polarization, and cyclic voltammetry. As the annealing temperature increased, the discharge capacity and anti-corrosion ability of the oxide electrode first increased and then decreased, reaching the optimum values at 600 ℃, with a maximum discharge capacity of 563 mA-h/g. The better electrochemical performance of LaFeO3 annealed at 600℃ could be ascribed to their smaller and more homogeneous crysals.展开更多
Perovskite oxides based on the alkaline earth metal lanthanum for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)in alkaline electrolytes are promising catalysts,but their catalytic activity and stabi...Perovskite oxides based on the alkaline earth metal lanthanum for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)in alkaline electrolytes are promising catalysts,but their catalytic activity and stability remain unsatisfactory.Here,we synthesized a series of LaFe1-xMn2O3(x=0,0.1,0.3,0.5,0.7,0.9 and 1)perovskite oxides by doping Mn into LaFeO3(LF).The results show that the doping amount of Mn has a significant effect on the catalytic performance.When x=0.5,the catalyst LaFeo.sMno.sO3(LFM)exhibits the best performance.The limiting current density in 0.1 mol·L^-1 KOH solution is 7 mA·cm^-2,much larger than that of the commercial Pt/C catalyst(5.5 mA·cm^-2).Meanwhile,the performance of the doped catalyst is also superior to that of commercial Pt/C in terms of the long-term durability.The excellent catalytic performance of LFM may be ascribed to its abundant 0^2-/0^-species and low charge transfer resistance after doping the Mn element.展开更多
LaFe03 perovskite with a porous fibrous structure was successfully synthesized using a sunflower seed shell as a template.To investigate the effects of this template,a sample was prepared without a template via the sa...LaFe03 perovskite with a porous fibrous structure was successfully synthesized using a sunflower seed shell as a template.To investigate the effects of this template,a sample was prepared without a template via the same procedure.Through various characterization techniques,such as X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,N2 adsorption-desorption analysis,X-ray photoelectron spectroscopy,oxygen temperature programed desorption,and hydrogen temperature programed reduction,the physiochemical properties of the samples were investigated.The results showed that the sample made with a template had a larger surface area and a larger amount of adsorbed oxygen,which further illustrated that the sunflower seed shell template had a significant impact on the physiochemical properties of the samples.Furthermore,we explored the catalytic activity for nitric oxide(NO)oxidation,and studied the factors affecting it,which highlighted its potential application in automobile exhausts.展开更多
基于密度泛函理论的第一性原理方法,通过计算表面能确定La Fe O_3(010)表面为最稳定的吸附表面,研究了H_2分子在La Fe O_3(010)表面的吸附性质。La Fe O_3(010)表面存在La O和Fe O_2两种终止表面,但吸附主要发生在Fe O_2终止表面,由于La...基于密度泛函理论的第一性原理方法,通过计算表面能确定La Fe O_3(010)表面为最稳定的吸附表面,研究了H_2分子在La Fe O_3(010)表面的吸附性质。La Fe O_3(010)表面存在La O和Fe O_2两种终止表面,但吸附主要发生在Fe O_2终止表面,由于La Fe O_3(010)表面弛豫的影响,使得凹凸不平的表面层增加了表面原子与H原子的接触面积,表面晶胞的纵向体积增加约2.5%,有利于H原子向晶体内扩散。研究发现,H_2分子在La Fe O_3(010)表面主要存在3种化学吸附方式:第一种吸附发生在O-O桥位,2个H原子分别吸附在2个O原子上,形成2个-OH基,这是最佳吸附位置,此时H原子与表面O原子的作用主要是H1s与O_2p轨道杂化作用的结果,H-O之间为典型的共价键。H_2分子的解离能垒为1.542 e V,说明表面需要一定的热条件,H_2分子才会发生解离吸附;第二种吸附发生在Fe-O桥位,1个H原子吸附在O原子上形成1个-OH基,另一个H原子吸附在Fe原子上形成金属键;第三种吸附发生在O顶位,2个H原子吸附在同一个O原子上,形成H_2O分子,此时H_2O分子与表面形成物理吸附,H_2O分子逃离表面后容易形成氧空位。此外,H_2分子在La Fe O_3(010)表面还可以发生物理吸附。展开更多
文摘制备具有氧还原(ORR)与氧释放(OER)双功能催化活性的特殊孔道结构电催化剂是锂氧电池研究的挑战之一。本文以氧化石墨烯、硝酸铁、硝酸镧、柠檬酸为原料,结合溶胶凝胶和水热合成方法,制备出还原氧化石墨烯(RGO)与铁酸镧(LaFeO_3)复合的双功能催化剂(RGO-LaFeO_3)。X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和Raman光谱分析结果确认该复合催化剂由纯相钙钛矿结构LaFeO_3和还原氧化石墨烯组成,扫描电子显微镜(SEM)观察到LaFeO_3纳米颗粒均匀地负载在RGO片层表面。锂氧电池测试结果指出,相对于LaFeO_3纳米粒子(NP-LaFeO_3),RGO-LaFeO_3催化剂具有更好的ORR和OER催化活性,归因于RGO特殊的三维导电多孔结构与LaFeO_3纳米粒子的协同催化作用。以RGO-LaFeO_3作为阴极催化剂的锂氧电池在限1000 m Ah?g^(-1)比容量、100 m A?g^(-1)电流密度条件下,可实现36周稳定的充放电循环,展示出良好的应用前景。
基金Supported by the National Natural Science Foundation of China（Nos. 51771164, 51571173 and 51701175）.
文摘We reported the effects of annealing temperatures on microstructure and electrochemical properties of perovskite-type oxide LaFeO3 prepared by stearic acid combustion method. X-Ray diffraction（XRD） patterns show that the annealed LaFeO3 powder has orthorhombic structure. Scanning electron microscopy（SEM） and transmission electron microscopy（TEM） images show the presence of homogeneously dispersed, less aggregated, and small crystals（30--40 nm） at annealing temperatures of 500 and 600 ℃. However, as the annealing temperature was increased to 700 and 800 ℃, the crystals began to combine with each other and grew into further larger crystals（90--100 nm）. The electrochemical performance of the annealed oxides was measured at 60 ℃ using chronopotentiometry, potentiodynamic polarization, and cyclic voltammetry. As the annealing temperature increased, the discharge capacity and anti-corrosion ability of the oxide electrode first increased and then decreased, reaching the optimum values at 600 ℃, with a maximum discharge capacity of 563 mA-h/g. The better electrochemical performance of LaFeO3 annealed at 600℃ could be ascribed to their smaller and more homogeneous crysals.
基金supported by the National Natural Science Foundation of China(Grants Nos.91745112,21604051,21671133 and 21507081)the Science and Technology Commission of Shanghai Municipality(Grant Nos.19DZ2271100,18020500800 and 18JC1412900).
文摘Perovskite oxides based on the alkaline earth metal lanthanum for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)in alkaline electrolytes are promising catalysts,but their catalytic activity and stability remain unsatisfactory.Here,we synthesized a series of LaFe1-xMn2O3(x=0,0.1,0.3,0.5,0.7,0.9 and 1)perovskite oxides by doping Mn into LaFeO3(LF).The results show that the doping amount of Mn has a significant effect on the catalytic performance.When x=0.5,the catalyst LaFeo.sMno.sO3(LFM)exhibits the best performance.The limiting current density in 0.1 mol·L^-1 KOH solution is 7 mA·cm^-2,much larger than that of the commercial Pt/C catalyst(5.5 mA·cm^-2).Meanwhile,the performance of the doped catalyst is also superior to that of commercial Pt/C in terms of the long-term durability.The excellent catalytic performance of LFM may be ascribed to its abundant 0^2-/0^-species and low charge transfer resistance after doping the Mn element.
基金the National Natural Science Foundation of China(Grant No.21607086)Zhejiang Province Public Welfare Technology Application Research Project(No.2016C33024)+3 种基金Scientific and Technological program of Ningbo City(Nos.2016C51025,2017C50031)Natural Science Foundation of Ningbo(No.2017A610061)Natural Science Foundation of Zhejiang Province(No.LY18B010003)K.C.Wong Magna Fund in Ningbo University.
文摘LaFe03 perovskite with a porous fibrous structure was successfully synthesized using a sunflower seed shell as a template.To investigate the effects of this template,a sample was prepared without a template via the same procedure.Through various characterization techniques,such as X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,N2 adsorption-desorption analysis,X-ray photoelectron spectroscopy,oxygen temperature programed desorption,and hydrogen temperature programed reduction,the physiochemical properties of the samples were investigated.The results showed that the sample made with a template had a larger surface area and a larger amount of adsorbed oxygen,which further illustrated that the sunflower seed shell template had a significant impact on the physiochemical properties of the samples.Furthermore,we explored the catalytic activity for nitric oxide(NO)oxidation,and studied the factors affecting it,which highlighted its potential application in automobile exhausts.
文摘基于密度泛函理论的第一性原理方法,通过计算表面能确定La Fe O_3(010)表面为最稳定的吸附表面,研究了H_2分子在La Fe O_3(010)表面的吸附性质。La Fe O_3(010)表面存在La O和Fe O_2两种终止表面,但吸附主要发生在Fe O_2终止表面,由于La Fe O_3(010)表面弛豫的影响,使得凹凸不平的表面层增加了表面原子与H原子的接触面积,表面晶胞的纵向体积增加约2.5%,有利于H原子向晶体内扩散。研究发现,H_2分子在La Fe O_3(010)表面主要存在3种化学吸附方式:第一种吸附发生在O-O桥位,2个H原子分别吸附在2个O原子上,形成2个-OH基,这是最佳吸附位置,此时H原子与表面O原子的作用主要是H1s与O_2p轨道杂化作用的结果,H-O之间为典型的共价键。H_2分子的解离能垒为1.542 e V,说明表面需要一定的热条件,H_2分子才会发生解离吸附;第二种吸附发生在Fe-O桥位,1个H原子吸附在O原子上形成1个-OH基,另一个H原子吸附在Fe原子上形成金属键;第三种吸附发生在O顶位,2个H原子吸附在同一个O原子上,形成H_2O分子,此时H_2O分子与表面形成物理吸附,H_2O分子逃离表面后容易形成氧空位。此外,H_2分子在La Fe O_3(010)表面还可以发生物理吸附。
文摘用柠檬酸法合成了钙钛矿型复合氧化物 La Fe O3,并按不同比例进行掺杂 ,制备了L a1-x Srx Fe O3( x=0 .0 1、0 .0 2、0 .0 3、0 .0 4、0 .0 5) .以荧光汞灯为光源测定了样品对不同染料的光催化降解活性 ,根据红外、紫外、光声光谱等技术对催化剂的分析结果 ,讨论了光催化性能及掺杂Sr2 +对其活性的影响 ,结果表明 ,掺杂后 L a Fe
