Porous carbon materials are widely used in particulate forms for energy applications such as fuel cells, batteries, and （super） capacitors. To better hold the particles together, polymeric additives are utilized as ...Porous carbon materials are widely used in particulate forms for energy applications such as fuel cells, batteries, and （super） capacitors. To better hold the particles together, polymeric additives are utilized as binders, which not only increase the weight and volume of the devices, but also cause adverse side effects. We developed a wood-derived, free-standing porous carbon electrode and successfully applied it as a cathode in Li-O2 batteries. The spontaneously formed hierarchical porous structure exhibits good performance in facilitating the mass transport and hosting the discharge products of Li202. Heteroatom （N） doping further improves the catalytic activity of the carbon cathode with lower overpotential and higher capacity. Overall, the Li-O2 battery based on the new carbon cathode affords a stable energy efficiency of 65% and can be operated for 20 cycles at a discharge depth of 70%. The wood-derived free-standing carbon represents a new, unique structure for energy applications.展开更多
Element sulfur in nature is an insulating solid.While it has been tested that one-dimensional sulfur chain is metallic and conducting,the investigation on two-dimensional sulfur remains elusive.We report that molybden...Element sulfur in nature is an insulating solid.While it has been tested that one-dimensional sulfur chain is metallic and conducting,the investigation on two-dimensional sulfur remains elusive.We report that molybdenum disulfide layers are able to serve as the nanotemplate to facilitate the formation of two-dimensional sulfur.Density functional theory calculations suggest that confined inbetween layers of molybdenum disulfide,sulfur atoms are able to form two-dimensional triangular arrays that are highly metallic.As a result,these arrays contribute to the high conductivity and metallic phase of the hybrid structures of molybdenum disulfide layers and two-dimensional sulfur arrays.The experimentally measured conductivity of such hybrid structures reaches up to 223 S/m.Multiple experimental results,including X-ray photoelectron spectroscopy(XPS),transition electron microscope(TEM),selected area electron diffraction(SAED),agree with the computational insights.Due to the excellent conductivity,the current density is linearly proportional to the scan rate until 30,000 mV s^(−1) without the attendance of conductive additives.Using such hybrid structures as electrode,the two-electrode supercapacitor cells yield a power density of 10^(6) Wh kg^(−1) and energy density ~47.5 Wh kg^(−1) in ionic liquid electrolytes.Our findings offer new insights into using two-dimensional materials and their Van der Waals heterostructures as nanotemplates to pattern foreign atoms for unprecedented material properties.展开更多
Polymers of intrinsic microporosity shows great potential for dye adsorption and magnetic Fe_(3)O_(4) are easy to be separated.In this work,hydrolyzed polymers of intrinsic microporosity-1/Fe_(3)O_(4) composite adsorb...Polymers of intrinsic microporosity shows great potential for dye adsorption and magnetic Fe_(3)O_(4) are easy to be separated.In this work,hydrolyzed polymers of intrinsic microporosity-1/Fe_(3)O_(4) composite adsorbents were prepared by phase inversion and hydrolysis process for cationic dye adsorption.The chemical structure and morphology of the composite adsorbents were systematically characterized by several characterization methods.Using methylene blue as the target dye,the influences of solution pH,contact time,initial dye concentration,and system temperature on the methylene blue adsorption process were investigated.The incorporation of Fe_(3)O_(4) particle into hydrolyzed polymers of intrinsic microporosity-1 endow the adsorbent with high magnetic saturation(20.7 emu·g^(–1))which allows the rapid separation of the adsorbent.Furthermore,the adsorption process was simulated by adsorption kinetics,isotherms and thermodynamics to gain insight onto the intrinsic adsorption mechanism.In addition,the composite adsorbents are able to selectively adsorb cationic dyes from mixed dyes solution.Hydrolyzed polymers of intrinsic microporosity/Fe_(3)O_(4) shows only a slight decrease for methylene blue adsorption after 10 adsorption/regeneration cycles,demonstrating the outstanding regeneration performance.The high adsorption capacity,outstanding regeneration ability,together with simple preparation method,endow the composite adsorbents great potential for selective removal of cationic dyes in wastewater system.展开更多
文摘Porous carbon materials are widely used in particulate forms for energy applications such as fuel cells, batteries, and （super） capacitors. To better hold the particles together, polymeric additives are utilized as binders, which not only increase the weight and volume of the devices, but also cause adverse side effects. We developed a wood-derived, free-standing porous carbon electrode and successfully applied it as a cathode in Li-O2 batteries. The spontaneously formed hierarchical porous structure exhibits good performance in facilitating the mass transport and hosting the discharge products of Li202. Heteroatom （N） doping further improves the catalytic activity of the carbon cathode with lower overpotential and higher capacity. Overall, the Li-O2 battery based on the new carbon cathode affords a stable energy efficiency of 65% and can be operated for 20 cycles at a discharge depth of 70%. The wood-derived free-standing carbon represents a new, unique structure for energy applications.
基金the financial startup support and Tier 1 award from Northeastern University。
文摘Element sulfur in nature is an insulating solid.While it has been tested that one-dimensional sulfur chain is metallic and conducting,the investigation on two-dimensional sulfur remains elusive.We report that molybdenum disulfide layers are able to serve as the nanotemplate to facilitate the formation of two-dimensional sulfur.Density functional theory calculations suggest that confined inbetween layers of molybdenum disulfide,sulfur atoms are able to form two-dimensional triangular arrays that are highly metallic.As a result,these arrays contribute to the high conductivity and metallic phase of the hybrid structures of molybdenum disulfide layers and two-dimensional sulfur arrays.The experimentally measured conductivity of such hybrid structures reaches up to 223 S/m.Multiple experimental results,including X-ray photoelectron spectroscopy(XPS),transition electron microscope(TEM),selected area electron diffraction(SAED),agree with the computational insights.Due to the excellent conductivity,the current density is linearly proportional to the scan rate until 30,000 mV s^(−1) without the attendance of conductive additives.Using such hybrid structures as electrode,the two-electrode supercapacitor cells yield a power density of 10^(6) Wh kg^(−1) and energy density ~47.5 Wh kg^(−1) in ionic liquid electrolytes.Our findings offer new insights into using two-dimensional materials and their Van der Waals heterostructures as nanotemplates to pattern foreign atoms for unprecedented material properties.
基金supported by the National Natural Science Foundation of China(Grant Nos.22178327 and 52003250)China Postdoctoral Science Foundation(Grant No.2020M682351)+1 种基金Excellent Youth Foundation of Henan Scientific Committee(Grant No.222300420018)Key Scientific Research Project of Universities in Henan Province(Grant No.21zx006).
文摘Polymers of intrinsic microporosity shows great potential for dye adsorption and magnetic Fe_(3)O_(4) are easy to be separated.In this work,hydrolyzed polymers of intrinsic microporosity-1/Fe_(3)O_(4) composite adsorbents were prepared by phase inversion and hydrolysis process for cationic dye adsorption.The chemical structure and morphology of the composite adsorbents were systematically characterized by several characterization methods.Using methylene blue as the target dye,the influences of solution pH,contact time,initial dye concentration,and system temperature on the methylene blue adsorption process were investigated.The incorporation of Fe_(3)O_(4) particle into hydrolyzed polymers of intrinsic microporosity-1 endow the adsorbent with high magnetic saturation(20.7 emu·g^(–1))which allows the rapid separation of the adsorbent.Furthermore,the adsorption process was simulated by adsorption kinetics,isotherms and thermodynamics to gain insight onto the intrinsic adsorption mechanism.In addition,the composite adsorbents are able to selectively adsorb cationic dyes from mixed dyes solution.Hydrolyzed polymers of intrinsic microporosity/Fe_(3)O_(4) shows only a slight decrease for methylene blue adsorption after 10 adsorption/regeneration cycles,demonstrating the outstanding regeneration performance.The high adsorption capacity,outstanding regeneration ability,together with simple preparation method,endow the composite adsorbents great potential for selective removal of cationic dyes in wastewater system.
