A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material charac...A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m2/g and 0.308 4 cm3/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance.展开更多
Clean catalytic oxidation has a broad prospect in the modern chemical engineering and energy chemistry fields.However,unexpected over-oxidation and disruptive degradation are frequently induced by excessive reactive o...Clean catalytic oxidation has a broad prospect in the modern chemical engineering and energy chemistry fields.However,unexpected over-oxidation and disruptive degradation are frequently induced by excessive reactive oxygen species(ROS).Herein,we reported a new ROS-free approach to effectively drive O_(2) to be activated into highly reactive surface peroxo species through enzyme-mimicking mechanism.Benefiting from the dual-metal synergy effect between Cu and Co active sites,ROS(H_(2)O_(2) and OH•)is generated in situ while further scavenged completely into surface peroxo species,which gives rise to very high selectivity and extremely high carbon balance.For example,the CuCo/N-C catalyst affords>99.8%conversion and 94.5%selectivity to 2,5-furanedicarboxylic acid at 25℃ for 6 h in the aerobic oxidation of biomass platform 5-hydroxymethylfurfural.Moreover,it achieved exceptional performance in the oxidation of a variety of hydroxyl compounds to organic acids with high yields(89.9%–99.5%)at a mild temperature(25–40℃).This exploration introduces an innovative clue for emulating enzyme catalysts,thereby enriching our comprehension and advancement of biologically inspired catalytic oxidations.展开更多
Oxygen evolution reaction （OER） electrolysis, as an important reaction involved in water splitting and rechargeable metal-air batteries, has attracted increasing attention for clean energy generation and efficient e...Oxygen evolution reaction （OER） electrolysis, as an important reaction involved in water splitting and rechargeable metal-air batteries, has attracted increasing attention for clean energy generation and efficient energy storage. Nickel/iron （NiFe）-based compounds have been known as active OER catalysts since the last century, and renewed interest has been witnessed in recent years on developing advanced NiFe-based materials for better activity and stability. In this review, we present the early discovery and recent progress on NiFe-based OER electrocatalysts in terms of chemical properties, synthetic methodologies and catalytic performances. The advantages and disadvantages of each class of NiFe-based compounds are summarized, including NiFe alloys, electrodeposited films and layered double hydroxide nanoplates. Some mechanistic studies of the active phase of NiFe-based compounds are introduced and discussed to give insight into the nature of active catalytic sites, which could facilitate further improving NiFe based OER electrocatalysts. Finally, some applications of NiFe- based compounds for OER are described, including the development of an electrolyzer operating with a single AAA battery with voltage below 1.5 V and high performance rechargeable Zn-air batteries.展开更多
The sluggish oxygen evolution reaction （OER） is an important half-reaction of the electrochemical water-splitting reaction. Amorphous Fe/Ni composite oxides have high activity. In this work, we modified the aerosol ...The sluggish oxygen evolution reaction （OER） is an important half-reaction of the electrochemical water-splitting reaction. Amorphous Fe/Ni composite oxides have high activity. In this work, we modified the aerosol spray-assisted approach and obtained amorphous Fe-Ni-Ox solid-solution nanoparticles （Fe-Ni-Ox-NPs） approximately 20 nm in size by choosing iron/nickel acetylacetonates as raw materials instead of inorganic salts. The small-sized Fe-Ni-Ox-NPs were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） analysis, energy-dispersive X-ray spectroscopy （EDX）, and X-ray photoelectron spectroscopy （XPS）. Furthermore, an investigation of electrochemical OER performance suggests that the small-sized Fe-Ni-Ox-NPs have higher activity than the large-sized Fe-Ni-Ox-MPs. A small overpotential of 0.315 V was demanded to obtain a working current density of 50 mA/cm2, and the Tafel slope was as low as 38 mWdec.展开更多
The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fo...The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.It was then used as the catalyst for the preparation of polycarbonate diol(PCDL) via the transesterification between diphenyl carbonate(DPC) and 1,6-hexandiol(1,6-HD).Its catalytic activity in the transesterification process is evaluated by the yield of phenol,and its catalytic activity in the polycondensation process is determined by the number-average molecular weight(Mn) and the hydroxyl value.Compared to the triethylenediamine(C6H12N2),Mg-Al layered double hydroxide(Mg-Al LDH),sodium ethoxide(C2H5ONa) and sodium methoxide(CH3ONa),MOF-5 exhibits highest catalytic activity for the preparation of PCDL.Under reaction conditions(n(1,6-HD)/n(DPC) = 1.2,w(catalyst) = 0.03%,198 ℃),the yield of phenol is up to 90.1% and the PCDL shows highest Mn and lowest hydroxyl value.展开更多
基金Project(2007BAE12B01) supported by the National Key Technology Research and Development Program of China
文摘A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m2/g and 0.308 4 cm3/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance.
文摘Clean catalytic oxidation has a broad prospect in the modern chemical engineering and energy chemistry fields.However,unexpected over-oxidation and disruptive degradation are frequently induced by excessive reactive oxygen species(ROS).Herein,we reported a new ROS-free approach to effectively drive O_(2) to be activated into highly reactive surface peroxo species through enzyme-mimicking mechanism.Benefiting from the dual-metal synergy effect between Cu and Co active sites,ROS(H_(2)O_(2) and OH•)is generated in situ while further scavenged completely into surface peroxo species,which gives rise to very high selectivity and extremely high carbon balance.For example,the CuCo/N-C catalyst affords>99.8%conversion and 94.5%selectivity to 2,5-furanedicarboxylic acid at 25℃ for 6 h in the aerobic oxidation of biomass platform 5-hydroxymethylfurfural.Moreover,it achieved exceptional performance in the oxidation of a variety of hydroxyl compounds to organic acids with high yields(89.9%–99.5%)at a mild temperature(25–40℃).This exploration introduces an innovative clue for emulating enzyme catalysts,thereby enriching our comprehension and advancement of biologically inspired catalytic oxidations.
文摘Oxygen evolution reaction （OER） electrolysis, as an important reaction involved in water splitting and rechargeable metal-air batteries, has attracted increasing attention for clean energy generation and efficient energy storage. Nickel/iron （NiFe）-based compounds have been known as active OER catalysts since the last century, and renewed interest has been witnessed in recent years on developing advanced NiFe-based materials for better activity and stability. In this review, we present the early discovery and recent progress on NiFe-based OER electrocatalysts in terms of chemical properties, synthetic methodologies and catalytic performances. The advantages and disadvantages of each class of NiFe-based compounds are summarized, including NiFe alloys, electrodeposited films and layered double hydroxide nanoplates. Some mechanistic studies of the active phase of NiFe-based compounds are introduced and discussed to give insight into the nature of active catalytic sites, which could facilitate further improving NiFe based OER electrocatalysts. Finally, some applications of NiFe- based compounds for OER are described, including the development of an electrolyzer operating with a single AAA battery with voltage below 1.5 V and high performance rechargeable Zn-air batteries.
文摘The sluggish oxygen evolution reaction （OER） is an important half-reaction of the electrochemical water-splitting reaction. Amorphous Fe/Ni composite oxides have high activity. In this work, we modified the aerosol spray-assisted approach and obtained amorphous Fe-Ni-Ox solid-solution nanoparticles （Fe-Ni-Ox-NPs） approximately 20 nm in size by choosing iron/nickel acetylacetonates as raw materials instead of inorganic salts. The small-sized Fe-Ni-Ox-NPs were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） analysis, energy-dispersive X-ray spectroscopy （EDX）, and X-ray photoelectron spectroscopy （XPS）. Furthermore, an investigation of electrochemical OER performance suggests that the small-sized Fe-Ni-Ox-NPs have higher activity than the large-sized Fe-Ni-Ox-MPs. A small overpotential of 0.315 V was demanded to obtain a working current density of 50 mA/cm2, and the Tafel slope was as low as 38 mWdec.
基金supported by the Key Projects in the National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period (2006BAE02B03)Jiangsu Provincial Science & Technology Pillar Program (BE2010065)
文摘The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.It was then used as the catalyst for the preparation of polycarbonate diol(PCDL) via the transesterification between diphenyl carbonate(DPC) and 1,6-hexandiol(1,6-HD).Its catalytic activity in the transesterification process is evaluated by the yield of phenol,and its catalytic activity in the polycondensation process is determined by the number-average molecular weight(Mn) and the hydroxyl value.Compared to the triethylenediamine(C6H12N2),Mg-Al layered double hydroxide(Mg-Al LDH),sodium ethoxide(C2H5ONa) and sodium methoxide(CH3ONa),MOF-5 exhibits highest catalytic activity for the preparation of PCDL.Under reaction conditions(n(1,6-HD)/n(DPC) = 1.2,w(catalyst) = 0.03%,198 ℃),the yield of phenol is up to 90.1% and the PCDL shows highest Mn and lowest hydroxyl value.
