Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reactio...Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray di raction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity(RH) of 90% and gas hourly space velocity of 585,000 h-1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The e ciency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.展开更多
Manganese oxides supported by ZSM-5 zeolite(Mn/ZSM-5) as well as their further modified by Ce promoter were achieved by simple impregnation method for ozone catalytic decomposition. The yCe20Mn/ZSM-5–81 catalyst with...Manganese oxides supported by ZSM-5 zeolite(Mn/ZSM-5) as well as their further modified by Ce promoter were achieved by simple impregnation method for ozone catalytic decomposition. The yCe20Mn/ZSM-5–81 catalyst with 8% Ce loading showed the highest catalytic activity at relative humidity of 50% and a space velocity of 360 L/(g × hr), giving 93% conversion of 600 ppm O_(3) after 5 hr. Moreover, this sample still maintained highly activity and stability in humid air with 50%–70% relative humidity. Series of physicochemical characterization including X-ray diffraction, temperature-programmed technology(NH_3-TPD and H_(2)-TPR), X-ray photoelectron spectroscopy and oxygen isotopic exchange were introduced to disclose the structure-performance relationship. The results indicated that moderate Si/Al ratio(81) of zeolite support was beneficial for ozone decomposition owing to the synergies of acidity and hydrophobicity. Furthermore, compared with 20 Mn/ZSM-5-81, Ce doping could enhance the amount of low valance manganese(such as Mn^(2+) and Mn^(3+)). Besides, the Ce^(3+)/Ce^(4+) ratio of 8Ce20Mn/ZSM-5-81 sample was higher than that of 4Ce_(2)0 Mn/ZSM-5-81. Additionally, the synergy between the MnO_x and CeO_(2) could easily transfer electron via the redox cycle, thus resulting in an increased reducibility at low temperatures and high concentration of surface oxygen. This study provides important insights to the utilization of porous zeolite with high surface area to disperse active component of manganese for ozone decomposition.展开更多
Uncoordinated lead in perovskites is a critical factor affecting solar cells’performance.It readily forms deep-level defects acting as nonradiative recombination centers,detrimental to power conversion efficiency.Thi...Uncoordinated lead in perovskites is a critical factor affecting solar cells’performance.It readily forms deep-level defects acting as nonradiative recombination centers,detrimental to power conversion efficiency.This work employs a synergistic passivation strategy using 12-crown-4 and phenethylammonium iodide at the interface between the wide-bandgap perovskite and the electron transport layer,addressing the insufficient passivation of uncoordinated lead defects by a single passivator.Results demonstrate that both phenethylammonium iodide and 12-crown-4 provide electrons to coordinate lead on the perovskite surface.However,synergistic passivation yields significantly greater gains in power conversion efficiency compared with either single passivator.It reduces nonradiative recombination,leading to increased steady-state photoluminescence intensity and prolonged transient carrier lifetime,consequently enhancing the open-circuit voltage.Furthermore,synergistic passivation increases recombination resistance and reduces series resistance,thereby improving the fill factor,without altering the perovskite structure or morphology.Based on this strategy,inverted wide-bandgap perovskite solar cells fabricated with the synergistic passivation achieved an efficiency of 21.63%,demonstrating great potential for high-efficiency perovskite tandem cells.展开更多
Diaphragm compressors have become the primary source of on-site hydrogen compression for hydrogen fuelling stations around the world.The most common hydrogen-compressor-failure mechanism has been identified as diaphra...Diaphragm compressors have become the primary source of on-site hydrogen compression for hydrogen fuelling stations around the world.The most common hydrogen-compressor-failure mechanism has been identified as diaphragm fracture due to low ten-sile strength and poor surface properties.In this study,a new type of GH4169 diaphragm with high yield strength and low surface roughness was fabricated.Microstructures,tensile behaviours and surface properties of the specimens were characterized by using scanning electron microscopy,an electronic universal testing machine and atomic force microscopy,respectively.The evolution of theandphases with temperature has been examined.Bothandphases were precipitant-strengthened phases for GH4169 and the volume and size ofandphases increase with ageing time.In addition,thephase is the main strengthening phase andis the supportive strengthening phase.Tensile strength was increased due to the strengthening phases at the cost of ductility.The roughness of the diaphragm could reach an arithmetic average roughness(Ra)of 0.1μm by applying a cooling-assisted polishing process.This work improves the reliability and reduces the auxiliary steps and down-time for diaphragm compressors.展开更多
Coal,a carbon-rich mineral with plentiful reserves,serves not only as a fuel but also as a raw material,presenting lower pollution emissions in the latter use.From a materials chemistry standpoint,coal is a viable raw...Coal,a carbon-rich mineral with plentiful reserves,serves not only as a fuel but also as a raw material,presenting lower pollution emissions in the latter use.From a materials chemistry standpoint,coal is a viable raw material for graphene production.This study develops a promising and sustainable method to convert coal into graphene,leveraging its unique macromolecular aromatic struc-ture and high carbon content.The investigation includes an analysis of the lateral size,morphology,and chemical composition of coal-derived graphene using techniques such as X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,and op-tical microscopy.Results confirm that coal can effectively replace natural graphite flakes in graphene production,with the derived graphene featuring three to six exfoliated layers and an oxygen content below 5.5%.While the graphene from coal shares a similar morphology to that derived from graphite,it exhibits more structural defects.Interestingly,the macroscopic size of the coal does not influence the microscopic composition and structure of the graphene.However,the thermal reduction method for oxidized graphene proves more effective at repairing structural defects than chemical reduction.Employing coal-derived graphene as a supercapacitor electrode demonstrates excellent cycling stability and ultra-high capacitance storage capacity.The H-CG-325 shows the highest dis-charge area-specific capacitance across various current densities.At an increased current density of 10 A/g,the H-CG-325 maintains 80.6%of its initial capacitance of 79 F/g observed at 1 A/g.Electrochemical tests reveal that coal-based graphene holds significant potential as a supercapacitor material,indicating promising applications in energy storage and conversion.展开更多
基金financial support from the National Natural Science Foundation of China (No. U1862102)the Fundamental Research Funds for the Central Universities (XK1802-1, JD1819)
文摘Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray di raction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity(RH) of 90% and gas hourly space velocity of 585,000 h-1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The e ciency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.
基金financially supported by the National Natural Science Foundation of China(Nos.U1862102,21976012)the Fundamental Research Funds for the Central Universities(XK1802-1,JD2016)。
文摘Manganese oxides supported by ZSM-5 zeolite(Mn/ZSM-5) as well as their further modified by Ce promoter were achieved by simple impregnation method for ozone catalytic decomposition. The yCe20Mn/ZSM-5–81 catalyst with 8% Ce loading showed the highest catalytic activity at relative humidity of 50% and a space velocity of 360 L/(g × hr), giving 93% conversion of 600 ppm O_(3) after 5 hr. Moreover, this sample still maintained highly activity and stability in humid air with 50%–70% relative humidity. Series of physicochemical characterization including X-ray diffraction, temperature-programmed technology(NH_3-TPD and H_(2)-TPR), X-ray photoelectron spectroscopy and oxygen isotopic exchange were introduced to disclose the structure-performance relationship. The results indicated that moderate Si/Al ratio(81) of zeolite support was beneficial for ozone decomposition owing to the synergies of acidity and hydrophobicity. Furthermore, compared with 20 Mn/ZSM-5-81, Ce doping could enhance the amount of low valance manganese(such as Mn^(2+) and Mn^(3+)). Besides, the Ce^(3+)/Ce^(4+) ratio of 8Ce20Mn/ZSM-5-81 sample was higher than that of 4Ce_(2)0 Mn/ZSM-5-81. Additionally, the synergy between the MnO_x and CeO_(2) could easily transfer electron via the redox cycle, thus resulting in an increased reducibility at low temperatures and high concentration of surface oxygen. This study provides important insights to the utilization of porous zeolite with high surface area to disperse active component of manganese for ozone decomposition.
基金supported by the National Natural Science Foundation of China(grant no.224611602812461160281)CHN Energy Investment Group Program(grant no.S930023048 and S930024020).
文摘Uncoordinated lead in perovskites is a critical factor affecting solar cells’performance.It readily forms deep-level defects acting as nonradiative recombination centers,detrimental to power conversion efficiency.This work employs a synergistic passivation strategy using 12-crown-4 and phenethylammonium iodide at the interface between the wide-bandgap perovskite and the electron transport layer,addressing the insufficient passivation of uncoordinated lead defects by a single passivator.Results demonstrate that both phenethylammonium iodide and 12-crown-4 provide electrons to coordinate lead on the perovskite surface.However,synergistic passivation yields significantly greater gains in power conversion efficiency compared with either single passivator.It reduces nonradiative recombination,leading to increased steady-state photoluminescence intensity and prolonged transient carrier lifetime,consequently enhancing the open-circuit voltage.Furthermore,synergistic passivation increases recombination resistance and reduces series resistance,thereby improving the fill factor,without altering the perovskite structure or morphology.Based on this strategy,inverted wide-bandgap perovskite solar cells fabricated with the synergistic passivation achieved an efficiency of 21.63%,demonstrating great potential for high-efficiency perovskite tandem cells.
文摘Diaphragm compressors have become the primary source of on-site hydrogen compression for hydrogen fuelling stations around the world.The most common hydrogen-compressor-failure mechanism has been identified as diaphragm fracture due to low ten-sile strength and poor surface properties.In this study,a new type of GH4169 diaphragm with high yield strength and low surface roughness was fabricated.Microstructures,tensile behaviours and surface properties of the specimens were characterized by using scanning electron microscopy,an electronic universal testing machine and atomic force microscopy,respectively.The evolution of theandphases with temperature has been examined.Bothandphases were precipitant-strengthened phases for GH4169 and the volume and size ofandphases increase with ageing time.In addition,thephase is the main strengthening phase andis the supportive strengthening phase.Tensile strength was increased due to the strengthening phases at the cost of ductility.The roughness of the diaphragm could reach an arithmetic average roughness(Ra)of 0.1μm by applying a cooling-assisted polishing process.This work improves the reliability and reduces the auxiliary steps and down-time for diaphragm compressors.
基金sponsored by the China Energy Investment Corporation under grant no.GJNY-21-85.
文摘Coal,a carbon-rich mineral with plentiful reserves,serves not only as a fuel but also as a raw material,presenting lower pollution emissions in the latter use.From a materials chemistry standpoint,coal is a viable raw material for graphene production.This study develops a promising and sustainable method to convert coal into graphene,leveraging its unique macromolecular aromatic struc-ture and high carbon content.The investigation includes an analysis of the lateral size,morphology,and chemical composition of coal-derived graphene using techniques such as X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,and op-tical microscopy.Results confirm that coal can effectively replace natural graphite flakes in graphene production,with the derived graphene featuring three to six exfoliated layers and an oxygen content below 5.5%.While the graphene from coal shares a similar morphology to that derived from graphite,it exhibits more structural defects.Interestingly,the macroscopic size of the coal does not influence the microscopic composition and structure of the graphene.However,the thermal reduction method for oxidized graphene proves more effective at repairing structural defects than chemical reduction.Employing coal-derived graphene as a supercapacitor electrode demonstrates excellent cycling stability and ultra-high capacitance storage capacity.The H-CG-325 shows the highest dis-charge area-specific capacitance across various current densities.At an increased current density of 10 A/g,the H-CG-325 maintains 80.6%of its initial capacitance of 79 F/g observed at 1 A/g.Electrochemical tests reveal that coal-based graphene holds significant potential as a supercapacitor material,indicating promising applications in energy storage and conversion.
