Manganese-based cathode materials are considered as a promising candidate for rechargeable aqueous zinc-ion batteries(ZIBs).Suffering from poor conductive and limited structure tolerance,various carbon matrix,especial...Manganese-based cathode materials are considered as a promising candidate for rechargeable aqueous zinc-ion batteries(ZIBs).Suffering from poor conductive and limited structure tolerance,various carbon matrix,especially N-doped carbon,were employed to incorporate with MnO_(2)for greatly promoted electrochemical performances.However,the related underlying mechanism is still unknown,which is unfavorable to guide the design of high performance electrode.Herein,by incorporating layered MnO_(2)with N-doped carbon nanowires,a free-standing cathode with hierarchical core-shell structure(denoted as MnO_(2)@NC)is prepared.Benefiting from the N-doped carbon and rational architecture,the MnO_(2)@NC electrode shows an enhanced specific capacity(325 mAh g^(−1)at 0.1 A g^(−1))and rate performance(90 mAh g^(−1)at 2 A g^(−1)),as well as improved cycling stability.Furthermore,the performance improvement mechanism of MnO_(2)incorporated by N-doped carbon is investigated by X-ray photoelectron spectroscopy(XPS),Raman spectrums and density functional theory(DFT)calculation.The N atom elongates the Mn-O bond and reduces the valence of Mn^(4+)ion in MnO_(2)crystal by delocalizing its electron clouds.Thus,the electrostatic repulsion will be weakened when Zn^(2+)/H^(+)insert into the host MnO_(2)lattices,which is profitable to more cation insertion and faster ion transfer kinetics for higher capacity and rate capability.This work elucidates a fundamental understanding of the functions of N-doped carbon in composite materials and shed light on a practical pathway to optimize other electrode materials.展开更多
The delamination of birnessite MnO_(2) into nanosheets by freezing and thawing method was reported here.The proton⁃type birnessite manganese oxide(H⁃birnessite)was added to tetramethylammonium hydroxide(TMAOH)solution...The delamination of birnessite MnO_(2) into nanosheets by freezing and thawing method was reported here.The proton⁃type birnessite manganese oxide(H⁃birnessite)was added to tetramethylammonium hydroxide(TMAOH)solution in a polypropylene tube which was then sealed.Fifty cycles consisting of fast freezing(in liquid nitrogen for 30 s)and thawing(in 70℃ water for 30 min)were operated.The as⁃prepared slurry was characterized by X⁃ray diffraction(XRD)and transmission electron microscope(TEM).The XRD result showed the layered structural H⁃birnessite was delaminated.The TEM result revealed the product had a nanosheet⁃like morphology.Employed as an anode material for lithium⁃ion batteries,MnO_(2) nanosheets as⁃prepared delivered a specific charging capacity of 1040.6 mAh/g after 100 cycles at 100 mA/g.展开更多
Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dend...Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dendritic Li formation,dramatical volume variation and serious pulverization.Herein,manganese dioxide (MnO_(2)) nanosheet modified nitrogen (N),phosphorus (P) co-doping carbon nanofibers(NPC) on carbon cloth (CC)(MnO_(2)@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC(Li-Mn@NPC-CC) electrode.The synergy of MnO_(2) and NPC obviously increases the reaction rate between MnO_(2)@NPC-CC and Li and guides even Li distribution over infusion process.Additionally,theoretical calculation,simulation and experimental results further indicate that N,P,Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC,which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles.Moreover,conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC,but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling.Hence,Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV.When the LiMn@NPC-CC anode couples with air,Li iron phosphate (LiFePO_(4)),or hard carbon (C) cathode,the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties.Especially,the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.展开更多
The electrochemical N_(2)reduction reaction(NRR)represents a green and sustainable route for NH_(3)synthesis under ambient conditions.However,the mechanism of N_(2)activation in the electrocatalytic NRR remains unclea...The electrochemical N_(2)reduction reaction(NRR)represents a green and sustainable route for NH_(3)synthesis under ambient conditions.However,the mechanism of N_(2)activation in the electrocatalytic NRR remains unclear.Herein,we found that the high spin state Mn^(3+)-Mn^(3+)pairs induced by oxygen vacancy in MnO_(2)nanosheets greatly enhance the catalytic activities.The strong electron transfer between d orbital of Mn and orbital of N2 forces the N_(2)to be of radical nature,which activates the hydrogenation process and weakens the N≡N bond.Based on the density functional theory(DFT)calculation results,we precisely designed mesoporous MnO_(2)nanosheets with rich oxygen vacancies via using methyltriphenylphosphonium bromide(MPB)to induce more Mn^(3+)-Mn^(3+)pairs(Mn^(3-3)-MnO_(2)),which can achieve a fairly high ammonia yield of up to 147.2μg·h^(−1)·mgcat−1.at−0.75 V vs.reversible hydrogen electrode(RHE)and a high Faradaic efficiency(FE)of 11%.Furthermore,these mesoporous MnO_(2)nanosheets exhibit the superior durability with negligible changes in both NH3 yield and FE after a consecutive 6-recycle test and the current density electrolyzed over a 24-hour period.Our findings offer an approach to designing highly active transition metal catalysts for electrocatalytic nitrogen reduction.展开更多
The sensitive and rapid detection of blood glucose is very important for monitoring and managing diabetes.Herein,a fluorescent/magnetic bimodal sensing strategy is proposed for glucose detection using a multifunction-...The sensitive and rapid detection of blood glucose is very important for monitoring and managing diabetes.Herein,a fluorescent/magnetic bimodal sensing strategy is proposed for glucose detection using a multifunction-responsive nanocomposite(MoS_(2)QDs-MnO_(2)NS).MoS_(2)QDs act as fluorescent probes,and MnO_(2)nanosheets are used as both quenchers and recognizers in this sensing platform.In the presence of glucose-mediated enzyme product(H_(2)O_(2)),MnO_(2)nanosheet is etched,thus releasing MoS_(2)QDs and Mn^(2+)ions,which causes the significantly enhancement of fluorescent and magnetic signals.Furthermore,MoS_(2)QDs-MnO_(2)NS-based fluorescent test paper is constructed for H_(2)O_(2)sensing with the naked eyes.Under optimal conditions,the dual linear ranges of 20-300μmol/L and 40-250μmol/L toward glucose detection are obtained for the fluorescent and magnetic mode,respectively.Furthermore,this bimodal assay exhibits good reproducibility and acceptable accuracy in glucose detection of clinical samples,demonstrating great versatility and flexibility of multifunctional probes in glucose detection.展开更多
We established a f uorescence“turn-on”sensing platform for glutathione(GSH)detection utilizing chitosan-based glutaraldehyde non-conjugated polymers(GCPF)as nanomaterials via f uorescence resonance energy transfer(F...We established a f uorescence“turn-on”sensing platform for glutathione(GSH)detection utilizing chitosan-based glutaraldehyde non-conjugated polymers(GCPF)as nanomaterials via f uorescence resonance energy transfer(FRET)principle.Owing to the overlapping property of absorption spectrum of MnO^(2)nanosheets with f uorescence spectrum of GCPF,f uorescent intensity of GCPF was quenched in the presence of MnO^(2)nanosheets because of FRET principle.When GSH was added,MnO^(2)nanosheets were reduced and decomposed into large amounts of Mn^(2+)ions owing to reducing property of GSH.Accordingly,the quenched f uorescent intensity was turned on again.Therefore,this platform based on MnO^(2)nanosheet has been f rst applied to f uorescence“turn-on”detection of GSH from 0.5 to 50μmol/L with sdetection limit of 84 nmol/L.It showed high selectivity in GSH detection towards other ions and biomolecules such as L-lysine,L-threonine,L-valine,L-glutamic acid and DL-aspartic acid.When it was utilized in detecting GSH in serum samples,satisfactory recoveries ranged from 101.5%to 103.2%,indicating the accuracy of this f uorescence“turn-on”platform in bioanalysis.展开更多
基金supported by National Natural Science Foundation of China(Nos.U20A20246,51872108)the Fundamental Research Funds for the Central Universities(Nos.30106200463 and CCNU20TS006)Graduate Education Innovation Grant from Central China Normal University(No.2020CXZZ101).
文摘Manganese-based cathode materials are considered as a promising candidate for rechargeable aqueous zinc-ion batteries(ZIBs).Suffering from poor conductive and limited structure tolerance,various carbon matrix,especially N-doped carbon,were employed to incorporate with MnO_(2)for greatly promoted electrochemical performances.However,the related underlying mechanism is still unknown,which is unfavorable to guide the design of high performance electrode.Herein,by incorporating layered MnO_(2)with N-doped carbon nanowires,a free-standing cathode with hierarchical core-shell structure(denoted as MnO_(2)@NC)is prepared.Benefiting from the N-doped carbon and rational architecture,the MnO_(2)@NC electrode shows an enhanced specific capacity(325 mAh g^(−1)at 0.1 A g^(−1))and rate performance(90 mAh g^(−1)at 2 A g^(−1)),as well as improved cycling stability.Furthermore,the performance improvement mechanism of MnO_(2)incorporated by N-doped carbon is investigated by X-ray photoelectron spectroscopy(XPS),Raman spectrums and density functional theory(DFT)calculation.The N atom elongates the Mn-O bond and reduces the valence of Mn^(4+)ion in MnO_(2)crystal by delocalizing its electron clouds.Thus,the electrostatic repulsion will be weakened when Zn^(2+)/H^(+)insert into the host MnO_(2)lattices,which is profitable to more cation insertion and faster ion transfer kinetics for higher capacity and rate capability.This work elucidates a fundamental understanding of the functions of N-doped carbon in composite materials and shed light on a practical pathway to optimize other electrode materials.
基金Sponsored by the China Postdoctoral Science Foundation(Grant No.2016M592746).
文摘The delamination of birnessite MnO_(2) into nanosheets by freezing and thawing method was reported here.The proton⁃type birnessite manganese oxide(H⁃birnessite)was added to tetramethylammonium hydroxide(TMAOH)solution in a polypropylene tube which was then sealed.Fifty cycles consisting of fast freezing(in liquid nitrogen for 30 s)and thawing(in 70℃ water for 30 min)were operated.The as⁃prepared slurry was characterized by X⁃ray diffraction(XRD)and transmission electron microscope(TEM).The XRD result showed the layered structural H⁃birnessite was delaminated.The TEM result revealed the product had a nanosheet⁃like morphology.Employed as an anode material for lithium⁃ion batteries,MnO_(2) nanosheets as⁃prepared delivered a specific charging capacity of 1040.6 mAh/g after 100 cycles at 100 mA/g.
基金funding support from the National Natural Science Foundation of China (21905151 and 51772162)the Youth Innovation and Technology Foundation of Shandong Higher Education Institutions, China (2019KJC004)+1 种基金the Outstanding Youth Foundation of Shandong Province, China (ZR2019JQ14)the Taishan Scholar Young Talent Program, Major Scientific and Technological Innovation Project (2019JZZY020405)。
文摘Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dendritic Li formation,dramatical volume variation and serious pulverization.Herein,manganese dioxide (MnO_(2)) nanosheet modified nitrogen (N),phosphorus (P) co-doping carbon nanofibers(NPC) on carbon cloth (CC)(MnO_(2)@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC(Li-Mn@NPC-CC) electrode.The synergy of MnO_(2) and NPC obviously increases the reaction rate between MnO_(2)@NPC-CC and Li and guides even Li distribution over infusion process.Additionally,theoretical calculation,simulation and experimental results further indicate that N,P,Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC,which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles.Moreover,conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC,but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling.Hence,Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV.When the LiMn@NPC-CC anode couples with air,Li iron phosphate (LiFePO_(4)),or hard carbon (C) cathode,the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties.Especially,the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.
基金financial support from the National Nature Science Foundation of China(No.22122113)National Key Research and Development Program of China(No.2021YFB4000405).
文摘The electrochemical N_(2)reduction reaction(NRR)represents a green and sustainable route for NH_(3)synthesis under ambient conditions.However,the mechanism of N_(2)activation in the electrocatalytic NRR remains unclear.Herein,we found that the high spin state Mn^(3+)-Mn^(3+)pairs induced by oxygen vacancy in MnO_(2)nanosheets greatly enhance the catalytic activities.The strong electron transfer between d orbital of Mn and orbital of N2 forces the N_(2)to be of radical nature,which activates the hydrogenation process and weakens the N≡N bond.Based on the density functional theory(DFT)calculation results,we precisely designed mesoporous MnO_(2)nanosheets with rich oxygen vacancies via using methyltriphenylphosphonium bromide(MPB)to induce more Mn^(3+)-Mn^(3+)pairs(Mn^(3-3)-MnO_(2)),which can achieve a fairly high ammonia yield of up to 147.2μg·h^(−1)·mgcat−1.at−0.75 V vs.reversible hydrogen electrode(RHE)and a high Faradaic efficiency(FE)of 11%.Furthermore,these mesoporous MnO_(2)nanosheets exhibit the superior durability with negligible changes in both NH3 yield and FE after a consecutive 6-recycle test and the current density electrolyzed over a 24-hour period.Our findings offer an approach to designing highly active transition metal catalysts for electrocatalytic nitrogen reduction.
基金financially supported by the Natural Science Foundation of Guangdong Province(No.2018A0303130002)the National Natural Science Foundation of China(No.81773684)+2 种基金Guangdong Natural Science Funds for Distinguished Young Scholars(No.2018B030306033)Pearl River Talent Program(No.2017GC010363)Pearl River S&T Nova Program of Guangzhou(No.201806010060)。
文摘The sensitive and rapid detection of blood glucose is very important for monitoring and managing diabetes.Herein,a fluorescent/magnetic bimodal sensing strategy is proposed for glucose detection using a multifunction-responsive nanocomposite(MoS_(2)QDs-MnO_(2)NS).MoS_(2)QDs act as fluorescent probes,and MnO_(2)nanosheets are used as both quenchers and recognizers in this sensing platform.In the presence of glucose-mediated enzyme product(H_(2)O_(2)),MnO_(2)nanosheet is etched,thus releasing MoS_(2)QDs and Mn^(2+)ions,which causes the significantly enhancement of fluorescent and magnetic signals.Furthermore,MoS_(2)QDs-MnO_(2)NS-based fluorescent test paper is constructed for H_(2)O_(2)sensing with the naked eyes.Under optimal conditions,the dual linear ranges of 20-300μmol/L and 40-250μmol/L toward glucose detection are obtained for the fluorescent and magnetic mode,respectively.Furthermore,this bimodal assay exhibits good reproducibility and acceptable accuracy in glucose detection of clinical samples,demonstrating great versatility and flexibility of multifunctional probes in glucose detection.
基金financially supported by Chongqing Research Program(cstc2018jcyjAX0742)of Basic ResearchFrontier Technology,Scientific and Technological Research Program(KJQN201900521)of Chongqing Education Committee+1 种基金Scientific Research Fund(2019YJ0307)of Sichuan Provincial Science and Technology DepartmentDazhou Municipal Science Project(18YYJC0002)of Technology Bureau Application Foundation
文摘We established a f uorescence“turn-on”sensing platform for glutathione(GSH)detection utilizing chitosan-based glutaraldehyde non-conjugated polymers(GCPF)as nanomaterials via f uorescence resonance energy transfer(FRET)principle.Owing to the overlapping property of absorption spectrum of MnO^(2)nanosheets with f uorescence spectrum of GCPF,f uorescent intensity of GCPF was quenched in the presence of MnO^(2)nanosheets because of FRET principle.When GSH was added,MnO^(2)nanosheets were reduced and decomposed into large amounts of Mn^(2+)ions owing to reducing property of GSH.Accordingly,the quenched f uorescent intensity was turned on again.Therefore,this platform based on MnO^(2)nanosheet has been f rst applied to f uorescence“turn-on”detection of GSH from 0.5 to 50μmol/L with sdetection limit of 84 nmol/L.It showed high selectivity in GSH detection towards other ions and biomolecules such as L-lysine,L-threonine,L-valine,L-glutamic acid and DL-aspartic acid.When it was utilized in detecting GSH in serum samples,satisfactory recoveries ranged from 101.5%to 103.2%,indicating the accuracy of this f uorescence“turn-on”platform in bioanalysis.
