Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored ...Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored in porous nanomaterials is still challenging.Here,through the template-free S-assisted pyrolysis of low-cost Fe-salts with melamine(MA),porous alveolate Fe/g-C3N4 catalysts with high-density(Fe loading up to 17.7 wt%)and increased USCAD Fe sites were synthesized.The presence of a certain amount of S species in the Fe-salts/MA system plays an important role in the formation of USCAD S-Fe-salt/CN catalysts;the S species act as a"sacrificial carrier"to increase the dispersion of Fe species through Fe-S coordination and generate porous alveolate structure by escaping in the form of SO2 during pyrolysis.The S-Fe-salt/CN catalysts exhibit greatly promoted activity and reusability for degrading various organic pollutants in advanced oxidation processes compared to the corresponding Fe-salt/CN catalysts,due to the promoted accessibility of USCAD Fe sites by the porous alveolate structure.This S-assisted method exhibits good feasibility in a large variety of S species(thiourea,S powder,and NH4SCN)and Fe salts,providing a new avenue for the low-cost and large-scale synthesis of high-density USCAD metal/g-C3N4 catalysts.展开更多
Highly active and durable oxygen reduction reaction(ORR)catalysts with sufficient activity and stability of Pt are beneficial for the commercialization of proton exchange membrane fuel cells.Here we report an effectiv...Highly active and durable oxygen reduction reaction(ORR)catalysts with sufficient activity and stability of Pt are beneficial for the commercialization of proton exchange membrane fuel cells.Here we report an effective approach to prepare a composite catalyst comprising of ordered L1_(2)-Pt_(3)Fe intermetallic nanoparticles interact with single atom Fe-N_(x)-C_(y)active sites.The addition of Fe and the confinement effect of hierarchical porous structure limit the growth of intermetallic particle size(around2.5 nm).The ligand effect of the electron transfer from Fe to Pt and the synergistic interaction between L1_(2)-Pt_(3)Fe and Fe-N_(x)-C_(y)work together to reduce oxygen intermediates adsorption and improve kinetics process.Experimentally,the L1_(2)-Pt_(3)Fe/C_(Fe-N-C)catalyst shows high mass activity and specific activity at 1.010 A/mg_(Pt)and 1.166 mA/cm^(2),respectively,which are 5.8 and 5.1 times higher than those of commercial Pt/C(0.174 A/mg_(Pt)and 0.230mA/cm^(2)).Thanks to the more stable L1_(2)structure,L1_(2)-Pt_(3)Fe/C_(Fe-N-C)exhibits better durability(14mV E_(1/2)loss of L1_(2)-Pt_(3)Fe/C_(Fe-N-C)and 33 mV E_(1/2)loss of commercial Pt/C)after 30,000 cycles accelerated stress tests.The strategy to design and prepare small particle Pt-based intermetallic alloys coordinated with M-N-C active sites provides a new direction to obtain low-cost and easily prepared effective ORR catalysts.展开更多
Rechargeable zinc-air batteries(ZABs)hold significant promise for next-generation energy storage due to their unique advantages in safety,energy and cost.However,their commercial application remains hindered by the sl...Rechargeable zinc-air batteries(ZABs)hold significant promise for next-generation energy storage due to their unique advantages in safety,energy and cost.However,their commercial application remains hindered by the sluggish kinetics of the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),necessitating the development of highly efficient and durable electrocatalysts.Herein,we report a hierarchically mesoporous Fe-N-C catalyst(Fe-N/MPC_(S500))synthesized via a template-assisted method,which exhibits exceptional bifunctional ORR/OER performance.The Fe-N/MPC_(S500)catalyst achieves a positive ORR half-wave potential(0.86 V),along with a low OER over-potential of 510 mV at 10 mA cm^(2),surpassing those of most non-precious metal catalysts.Furthermore,in a liquid-state ZAB,Fe-N/MPC_(S500) delivers a high specific capacity of 708 mAh g^(-1),a peak power density of 409 mW cm^(2),and stable charge-discharge cycling over 470 h,outperforming commercial Pt/C+Ir/C catalysts.The outstanding performance is attributed to the hierarchical porosity,optimized Fe-N coordination,and enhanced electron/mass transport.This work presents a scalable and low-cost strategy for developing high-performance single-atom catalysts,paving the way for practical deployment in energy conversion and storage technologies.展开更多
Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four plan...Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four planar N-coordination and one axial P-coordination(Co-N_(4)P_(1))are decorated on the lateral edges of nanorod-like crystalline g-C_(3)N_(4)(CCN)photocatalysts.Significantly,the electronic structures of central Co as active sites for O_(2) reduction reaction(ORR)and planar N-coordinator as active sites for H_(2)O oxidation reaction(WOR)in Co-N_(4)P_(1) can be well regulated by the synergetic effects of introducing axial P-coordinator,in contrast to the decorated Co single-atoms with only four planar N-coordination(Co-N_(4)).Specifically,directional photoelectron accumulation at central Co active sites,induced by an introduced midgap level in Co-N_(4)P_(1),mediates the ORR active sites from 4e–-ORR-selective terminal–NH_(2) sites to 2e–-ORR-selective Co sites,moreover,an elevated d-band center of Co 3d orbital strengthens ORR intermediate*OOH adsorption,thus jointly facilitating a highly selective and active 2e^(–)-ORR pathway to H_(2)O_(2) photosynthesis.Simultaneously,a downshifted p-band center of N_(2)p orbital in Co-N_(4)P_(1) weakens WOR intermediate*OH adsorption,thus enabling a preferable 2e^(–)-WOR pathway toward H_(2)O_(2) photosynthesis.Subsequently,Co-N_(4)P_(1) exhibits exceptional H_(2)O_(2) photosynthesis efficiency,reaching 295.6μmol g^(-1) h^(-1) with a remarkable solar-to-chemical conversion efficiency of 0.32%,which is 15 times that of Co-N_(4)(19.2μmol g^(-1) h^(-1))and 10 times higher than CCN(27.6μmol g^(-1) h^(-1)).This electronic structure modulation on single-atom catalysts offers a promising strategy for boosting the activity and selectivity of H_(2)O_(2) photosynthesis.展开更多
As a novel alternative to traditional perfluoroalkyl substances(PFASs),including perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),hexafluoroproplyene oxide trimer acid(HFPO-TA)has been detected worldwid...As a novel alternative to traditional perfluoroalkyl substances(PFASs),including perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),hexafluoroproplyene oxide trimer acid(HFPO-TA)has been detected worldwide in surface water.Moreover,recent researches have demonstrated that HFPO-TA has stronger bioaccumulation potential and higher hepatotoxicity than PFOA.To treat these contaminants e.g.PFOA and PFOS,some photochemical techniques by adding exogenous substances had been reported.However,there is still no report for the behavior of HFPO-TA itself under direct UV irradiation.The current study investigated the photo-transformation of HFPO-TA under UV irradiation in aqueous solution.After 72 hr photoreaction,75%degradation ratio and 25%defluorination ratio were achieved under ambient condition.Reducing active species,i.e.,hydrated electrons and active hydrogen atoms,generated from water splitting played dominant roles in degradation of HFPO-TA,which was confirmed by different effects of reaction atmospheres and quenching experiments.A possible degradation pathway was proposed based on the products identification and theoretical calculations.In general,HFPO-TA would be transformed into shorter-chain PFASs,including hexafluoropropylene oxide dimer acid(HFPODA),perfluoropropionic acid(PFA)and trifluoroacetate(TFA).This research provides basic information for HFPO-TA photodegradation process and is essential to develop novel remediation techniques for HFPO-TA and other alternatives with similar structures.展开更多
Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge ...Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge to increase the number of atomically dispersed active sites on these catalysts.Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass.Two types of active catalyst centers were identified,namely atomically dispersed Fe sites and Fe_(x)P particles.The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe_(x)P particles.A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained,revealing the major contribution of the atomically dispersed Fe to the ORR activity.The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt%Fe,resulting in the maximum ORR rate.Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn^(-1),a power density of 92.9 m W cm^(-2) at 137 m A cm^(-2) and an excellent durability were exhibited.展开更多
In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharg...In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased, the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.展开更多
The mechanics of structural ceramics,especially the toughness,are crucial to their service reliability and need to be continuously optimized.Inspired by the“brick-mortar”structure and further adjusting the microstru...The mechanics of structural ceramics,especially the toughness,are crucial to their service reliability and need to be continuously optimized.Inspired by the“brick-mortar”structure and further adjusting the microstructure of“mortar”on the interface,ceramic with strength and toughness up to 444.16 MPa and 13.79 MPa⋅m^(1/2) is constructed by hot pressed sintering with alumina(Al_(2)O_(3))as brick and vertical graphene(VG)with active atomic edges as mortar.Relying on the covalent interface between VG grown in-situ and Al_(2)O_(3),the sliding of Al_(2)O_(3)links the shear-deformation process of the crosslinked and interlocked nanointerface formed by VG,making the VG-enhanced Al_(2)O_(3)ceramics(AVG)obtain super toughness.Moreover,the structure of interlocked VG-nanointerface exhibits an excellent high-temperature resistance,which makes AVG still show the excellent strength of 437.66 MPa and toughness of 11.16 MPa⋅m^(1/2)after heat treatment at 1500℃for 100 h and they are respective 2.51 times and 3.18 times higher than Al_(2)O_(3)in the same condition.This work provides a new thought for the preparation of high-strength,ultra-tough and high-temperature mechanical stable ceramics.展开更多
Photoredox catalysis has become an indispensable solution for the synthesis of small organic molecules.However,the precise construction of single-atomic active sites not only determines the catalytic performance,but a...Photoredox catalysis has become an indispensable solution for the synthesis of small organic molecules.However,the precise construction of single-atomic active sites not only determines the catalytic performance,but also avails the understanding of structure–activity relationship.Herein,we develop a facile approach to immobilize single-atom Ni sites anchored porous covalent organic framework(COF)by use of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,6-diformylpyridine(Ni SAS/TD-COF).Ni SAS/TDCOF catalyst achieves excellent catalytic performance in visible-light-driven catalytic carbon–nitrogen cross-coupling reaction between aryl bromides and amines under mild conditions.The reaction provides amine products in excellent yields(71%–97%)with a wide range of substrates,including aryl and heteroaryl bromides with electron-deficient,electron-rich and neutral groups.Notably,Ni SAS/TD-COF could be recovered from the reaction mixture,corresponding to the negligible loss of photoredox performance after several cycles.This work provides a promising opportunity upon rational design of single-atomic active sites on COFs and the fundamental insight of photoredox mechanism for sustainable organic transformation.展开更多
Chemical vapor deposition(CVD)using gaseous hydrocarbon sources has shown great promise for large-scale graphene growth,but high growth temperatures(typically 1000℃)require sophisticated and expensive equipment,which...Chemical vapor deposition(CVD)using gaseous hydrocarbon sources has shown great promise for large-scale graphene growth,but high growth temperatures(typically 1000℃)require sophisticated and expensive equipment,which increases graphene production costs.Here,we demonstrate a new approach to produce graphene at low cost from scrap steel sheets treated by thermal evaporation of copper plating,which is a derivative of traditional CVD technology.Without additional carbon sources,graphene film was successfully prepared on copper-coated scrap steel sheets at 820℃.The resulting graphene has few defects and uniform morphology,comparable to CVD graphene grown at 1000℃.Finally,the obtained graphene film is used in combination with an interdigital electrode to detect NO_(2)successfully,showing excellent performance.This technology expands the application of graphene in the manufacture of gas sensing devices and is compatible with traditional microelectronics technology.展开更多
文摘Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored in porous nanomaterials is still challenging.Here,through the template-free S-assisted pyrolysis of low-cost Fe-salts with melamine(MA),porous alveolate Fe/g-C3N4 catalysts with high-density(Fe loading up to 17.7 wt%)and increased USCAD Fe sites were synthesized.The presence of a certain amount of S species in the Fe-salts/MA system plays an important role in the formation of USCAD S-Fe-salt/CN catalysts;the S species act as a"sacrificial carrier"to increase the dispersion of Fe species through Fe-S coordination and generate porous alveolate structure by escaping in the form of SO2 during pyrolysis.The S-Fe-salt/CN catalysts exhibit greatly promoted activity and reusability for degrading various organic pollutants in advanced oxidation processes compared to the corresponding Fe-salt/CN catalysts,due to the promoted accessibility of USCAD Fe sites by the porous alveolate structure.This S-assisted method exhibits good feasibility in a large variety of S species(thiourea,S powder,and NH4SCN)and Fe salts,providing a new avenue for the low-cost and large-scale synthesis of high-density USCAD metal/g-C3N4 catalysts.
基金supported by the National Science and Technology Major Project(No.2017YFB0102900)National Natural Science Foundation of China(Nos.21633008,21673221 and U1601211)Jilin Province Science and Technology Development Program(Nos.20200201001JC,20190201270JC and 20180101030JC)。
文摘Highly active and durable oxygen reduction reaction(ORR)catalysts with sufficient activity and stability of Pt are beneficial for the commercialization of proton exchange membrane fuel cells.Here we report an effective approach to prepare a composite catalyst comprising of ordered L1_(2)-Pt_(3)Fe intermetallic nanoparticles interact with single atom Fe-N_(x)-C_(y)active sites.The addition of Fe and the confinement effect of hierarchical porous structure limit the growth of intermetallic particle size(around2.5 nm).The ligand effect of the electron transfer from Fe to Pt and the synergistic interaction between L1_(2)-Pt_(3)Fe and Fe-N_(x)-C_(y)work together to reduce oxygen intermediates adsorption and improve kinetics process.Experimentally,the L1_(2)-Pt_(3)Fe/C_(Fe-N-C)catalyst shows high mass activity and specific activity at 1.010 A/mg_(Pt)and 1.166 mA/cm^(2),respectively,which are 5.8 and 5.1 times higher than those of commercial Pt/C(0.174 A/mg_(Pt)and 0.230mA/cm^(2)).Thanks to the more stable L1_(2)structure,L1_(2)-Pt_(3)Fe/C_(Fe-N-C)exhibits better durability(14mV E_(1/2)loss of L1_(2)-Pt_(3)Fe/C_(Fe-N-C)and 33 mV E_(1/2)loss of commercial Pt/C)after 30,000 cycles accelerated stress tests.The strategy to design and prepare small particle Pt-based intermetallic alloys coordinated with M-N-C active sites provides a new direction to obtain low-cost and easily prepared effective ORR catalysts.
基金supported by the Shanghai Sailing Program(22YF1400700)the Chenguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(22CGA37)+3 种基金the Fundamental Research Funds for the Central Universities(2232022D-18)the National Natural Science Foundation of China(52302084)the Natural Science Foundation of Yancheng(YCBK2024004)the Jiaxing Science and Technology Project for Youth Talent(2024AY40016).
文摘Rechargeable zinc-air batteries(ZABs)hold significant promise for next-generation energy storage due to their unique advantages in safety,energy and cost.However,their commercial application remains hindered by the sluggish kinetics of the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),necessitating the development of highly efficient and durable electrocatalysts.Herein,we report a hierarchically mesoporous Fe-N-C catalyst(Fe-N/MPC_(S500))synthesized via a template-assisted method,which exhibits exceptional bifunctional ORR/OER performance.The Fe-N/MPC_(S500)catalyst achieves a positive ORR half-wave potential(0.86 V),along with a low OER over-potential of 510 mV at 10 mA cm^(2),surpassing those of most non-precious metal catalysts.Furthermore,in a liquid-state ZAB,Fe-N/MPC_(S500) delivers a high specific capacity of 708 mAh g^(-1),a peak power density of 409 mW cm^(2),and stable charge-discharge cycling over 470 h,outperforming commercial Pt/C+Ir/C catalysts.The outstanding performance is attributed to the hierarchical porosity,optimized Fe-N coordination,and enhanced electron/mass transport.This work presents a scalable and low-cost strategy for developing high-performance single-atom catalysts,paving the way for practical deployment in energy conversion and storage technologies.
文摘Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four planar N-coordination and one axial P-coordination(Co-N_(4)P_(1))are decorated on the lateral edges of nanorod-like crystalline g-C_(3)N_(4)(CCN)photocatalysts.Significantly,the electronic structures of central Co as active sites for O_(2) reduction reaction(ORR)and planar N-coordinator as active sites for H_(2)O oxidation reaction(WOR)in Co-N_(4)P_(1) can be well regulated by the synergetic effects of introducing axial P-coordinator,in contrast to the decorated Co single-atoms with only four planar N-coordination(Co-N_(4)).Specifically,directional photoelectron accumulation at central Co active sites,induced by an introduced midgap level in Co-N_(4)P_(1),mediates the ORR active sites from 4e–-ORR-selective terminal–NH_(2) sites to 2e–-ORR-selective Co sites,moreover,an elevated d-band center of Co 3d orbital strengthens ORR intermediate*OOH adsorption,thus jointly facilitating a highly selective and active 2e^(–)-ORR pathway to H_(2)O_(2) photosynthesis.Simultaneously,a downshifted p-band center of N_(2)p orbital in Co-N_(4)P_(1) weakens WOR intermediate*OH adsorption,thus enabling a preferable 2e^(–)-WOR pathway toward H_(2)O_(2) photosynthesis.Subsequently,Co-N_(4)P_(1) exhibits exceptional H_(2)O_(2) photosynthesis efficiency,reaching 295.6μmol g^(-1) h^(-1) with a remarkable solar-to-chemical conversion efficiency of 0.32%,which is 15 times that of Co-N_(4)(19.2μmol g^(-1) h^(-1))and 10 times higher than CCN(27.6μmol g^(-1) h^(-1)).This electronic structure modulation on single-atom catalysts offers a promising strategy for boosting the activity and selectivity of H_(2)O_(2) photosynthesis.
基金funded by the Chinese Academy of Engineering Consulting Project(No.2019-XZ-24)the National Key Re-search and Development Plans of Special Project for Site Soil(No.2018YFC1801002)。
文摘As a novel alternative to traditional perfluoroalkyl substances(PFASs),including perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),hexafluoroproplyene oxide trimer acid(HFPO-TA)has been detected worldwide in surface water.Moreover,recent researches have demonstrated that HFPO-TA has stronger bioaccumulation potential and higher hepatotoxicity than PFOA.To treat these contaminants e.g.PFOA and PFOS,some photochemical techniques by adding exogenous substances had been reported.However,there is still no report for the behavior of HFPO-TA itself under direct UV irradiation.The current study investigated the photo-transformation of HFPO-TA under UV irradiation in aqueous solution.After 72 hr photoreaction,75%degradation ratio and 25%defluorination ratio were achieved under ambient condition.Reducing active species,i.e.,hydrated electrons and active hydrogen atoms,generated from water splitting played dominant roles in degradation of HFPO-TA,which was confirmed by different effects of reaction atmospheres and quenching experiments.A possible degradation pathway was proposed based on the products identification and theoretical calculations.In general,HFPO-TA would be transformed into shorter-chain PFASs,including hexafluoropropylene oxide dimer acid(HFPODA),perfluoropropionic acid(PFA)and trifluoroacetate(TFA).This research provides basic information for HFPO-TA photodegradation process and is essential to develop novel remediation techniques for HFPO-TA and other alternatives with similar structures.
基金The financial supports from Department of Chemical Engineeringthe support from China Scholarship Council(CSC)for his study at NTNU。
文摘Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge to increase the number of atomically dispersed active sites on these catalysts.Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass.Two types of active catalyst centers were identified,namely atomically dispersed Fe sites and Fe_(x)P particles.The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe_(x)P particles.A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained,revealing the major contribution of the atomically dispersed Fe to the ORR activity.The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt%Fe,resulting in the maximum ORR rate.Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn^(-1),a power density of 92.9 m W cm^(-2) at 137 m A cm^(-2) and an excellent durability were exhibited.
基金The project supported by the United Fund of the National Natural Science Foundation of China and the Engineering Physics Institute of China (No. 10276008)the funding of Liaoning Province Natural Science Foundation (No. 20022138)
文摘In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased, the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.
基金supported by the National Natural Science Foundation of China under Grant Nos.52222204,52172103,52293371,52072304,and Natural Science Basic Research Program in Shaanxi(2022JC-25).
文摘The mechanics of structural ceramics,especially the toughness,are crucial to their service reliability and need to be continuously optimized.Inspired by the“brick-mortar”structure and further adjusting the microstructure of“mortar”on the interface,ceramic with strength and toughness up to 444.16 MPa and 13.79 MPa⋅m^(1/2) is constructed by hot pressed sintering with alumina(Al_(2)O_(3))as brick and vertical graphene(VG)with active atomic edges as mortar.Relying on the covalent interface between VG grown in-situ and Al_(2)O_(3),the sliding of Al_(2)O_(3)links the shear-deformation process of the crosslinked and interlocked nanointerface formed by VG,making the VG-enhanced Al_(2)O_(3)ceramics(AVG)obtain super toughness.Moreover,the structure of interlocked VG-nanointerface exhibits an excellent high-temperature resistance,which makes AVG still show the excellent strength of 437.66 MPa and toughness of 11.16 MPa⋅m^(1/2)after heat treatment at 1500℃for 100 h and they are respective 2.51 times and 3.18 times higher than Al_(2)O_(3)in the same condition.This work provides a new thought for the preparation of high-strength,ultra-tough and high-temperature mechanical stable ceramics.
基金supported by the National Natural Science Foundation of China(21972015 and 22088102)Young top talents project of Liaoning Province(XLYC1907147)+1 种基金the Liaoning Revitalization Talent Program(XLYC2008032)the Fundamental Research Funds for the Central Universities(DUT22LAB602)。
文摘Photoredox catalysis has become an indispensable solution for the synthesis of small organic molecules.However,the precise construction of single-atomic active sites not only determines the catalytic performance,but also avails the understanding of structure–activity relationship.Herein,we develop a facile approach to immobilize single-atom Ni sites anchored porous covalent organic framework(COF)by use of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,6-diformylpyridine(Ni SAS/TD-COF).Ni SAS/TDCOF catalyst achieves excellent catalytic performance in visible-light-driven catalytic carbon–nitrogen cross-coupling reaction between aryl bromides and amines under mild conditions.The reaction provides amine products in excellent yields(71%–97%)with a wide range of substrates,including aryl and heteroaryl bromides with electron-deficient,electron-rich and neutral groups.Notably,Ni SAS/TD-COF could be recovered from the reaction mixture,corresponding to the negligible loss of photoredox performance after several cycles.This work provides a promising opportunity upon rational design of single-atomic active sites on COFs and the fundamental insight of photoredox mechanism for sustainable organic transformation.
基金the National Natural Science Foundation of China(No.52073305)Natural Science Foundation of Shandong Province(No.ZR2020QE048)+1 种基金State Key Laboratory of Heavy Oil Processing(No.SKLHOP202101006)National Defense Science and Technology Innovation Special Zone Project(No.22-05-CXZX-04-04-29).
文摘Chemical vapor deposition(CVD)using gaseous hydrocarbon sources has shown great promise for large-scale graphene growth,but high growth temperatures(typically 1000℃)require sophisticated and expensive equipment,which increases graphene production costs.Here,we demonstrate a new approach to produce graphene at low cost from scrap steel sheets treated by thermal evaporation of copper plating,which is a derivative of traditional CVD technology.Without additional carbon sources,graphene film was successfully prepared on copper-coated scrap steel sheets at 820℃.The resulting graphene has few defects and uniform morphology,comparable to CVD graphene grown at 1000℃.Finally,the obtained graphene film is used in combination with an interdigital electrode to detect NO_(2)successfully,showing excellent performance.This technology expands the application of graphene in the manufacture of gas sensing devices and is compatible with traditional microelectronics technology.
