Owing to the distinctive structural characteristics,vanadium nitride(VN)is highly regarded as a catalyst for oxygen reduction reaction(ORR)in zinc-air batteries(ZABs).However,VN exhibits limited intrinsic ORR activity...Owing to the distinctive structural characteristics,vanadium nitride(VN)is highly regarded as a catalyst for oxygen reduction reaction(ORR)in zinc-air batteries(ZABs).However,VN exhibits limited intrinsic ORR activity due to the weak adsorption ability to O-containing species.Here,the S-doped VN anchored on N,S-doped multi-dimensional carbon(S-VN/Co/NS-MC)was constructed using the solvothermal and in-situ doping methods.Incorporating sulfur atoms into VN species alters the electron spin state of vanadium in the S-VN/Co/NS-MC for regulating the adsorption energy of vanadium sites to oxygen molecules.The introduced sulfur atoms polarize the V 3d_(z)^(2) electrons,shifting spin-down electrons closer to the Fermi level in the S-VN/Co/NS-MC.Consequently,the introduction of sulfur atoms into VN species enhances the adsorption energy of vanadium sites for oxygen molecules.The*OOH dissociation transitions from being unspontaneous on the VN surface to a spontaneous state on the S-doped VN surface.Then,the ORR barrier on the S-VN/Co/NS-MC surface is reduced.The S-VN/Co/NS-MC demonstrates a higher half-wave potential and limiting current density compared to the VN/Co/N-MC.The S-VN/Co/NS-MC-based liquid ZABs display a power density of 195.7 m W cm^(-2),a specific capacity of 815.7 m A h g^(-1),and a cycling stability exceeding 250 h.The S-VN/Co/NS-MC-based flexible ZABs are successfully employed to charge both a smart watch and a mobile phone.This approach holds promise for advancing the commercial utilization of VN-based catalysts in ZABs.展开更多
Molybdenum trioxide(MoO_(3))has recently attracted wide attention as a typical conversion-type anode of Li-ion batteries(LIBs).Nevertheless,the inferior intrinsic conductivity and rapid capacity fading during charge/d...Molybdenum trioxide(MoO_(3))has recently attracted wide attention as a typical conversion-type anode of Li-ion batteries(LIBs).Nevertheless,the inferior intrinsic conductivity and rapid capacity fading during charge/discharge process seriously limit large-scale commercial application of MoO_(3).Herein,the density function theory(DFT)calculations show that electron-proton co-doping preferentially bonds symmetric oxygen to form unstable HxMoO_(3).When the-OH-group in HxMoO_(3) is released into the solution in the form of H_(2)O,it is going to form MoO_(3-x)with lower binding energy.By the means of both electron-proton co-doping and high-energy nanosizing,oxygen vacancies and nanoflower structure are introduced into MoO_(3) to accelerate the ion and electronic diffusion/transport kinetics.Benefitting from the promotion of ion diffusion kinetics related to nanostructures,as well as both the augmentation of active sites and the improvement of electrical conductivity induced by oxygen vacancies,the MoO_(3-x)/nanoflower structures show excellent lithium-ion storage performance.The prepared specimen has a high lithium-ion storage capacity of 1261 mA h g^(-1)at 0.1 A g^(-1)and cyclic stability(450 cycle),remarkably higher than those of previously reported MoO_(3)-based anode materials.展开更多
Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation effici...Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation efficiency,remain as the bottleneck to achieve highly efficient hydrogen evolution.Here,a hollow oxygen-incorporated g-C3N4 nanosheet(OCN)with an improved surface area of 148.5 m2 g^−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere,wherein the C–O bonds are formed through two ways of physical adsorption and doping.The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects,leading to the formation of hollow morphology,while the O-doping results in reduced band gap of g-C3N4.The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6μmol g^−1 h^−1 for~20 h,which is over four times higher than that of g-C3N4(850.1μmol g^−1 h^−1)and outperforms most of the reported g-C3N4 catalysts.展开更多
The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope ...The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope （TEM）, and X-ray diffraction （XRD）. The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vo1% at the center and 6.77vo1% at the surface of the casting thin strip, in vermicular and hand shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3, Cr2O3, and FeO or their multiplicity oxides of MnO.Al2O3, 2FeO.SiO2, and 2MnO.SiO2. Many defects including dislocations and stacking faults have also formed during the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.展开更多
By constructing counterexamples,the authors show that the fixed subgroups are not compressed in direct products of free and surface groups,and hence negate a conjecture in[Zhang,Q.,Ventura,E.and J.Wu,Fixed subgroups a...By constructing counterexamples,the authors show that the fixed subgroups are not compressed in direct products of free and surface groups,and hence negate a conjecture in[Zhang,Q.,Ventura,E.and J.Wu,Fixed subgroups are compressed in surface groups,Internat.J.Algebra Comput.,25,2015,865–887].展开更多
The microstructure design of electrode material is a crucial point to optimize the supercapacitor’s electrochemical properties.In this work,a Bi-based nanocomposite with a three-layer structure(Bi–Bi_(2)O_(3)@carbon...The microstructure design of electrode material is a crucial point to optimize the supercapacitor’s electrochemical properties.In this work,a Bi-based nanocomposite with a three-layer structure(Bi–Bi_(2)O_(3)@carbon armour(CA)/carbon dots(CDs))is synthesized and investigated.This material inherits high capacitance and high activity from bismuth-based materials,the coated CA protects the structure from complete oxidization and improves surface hydrophilicity.Furthermore,CDs in CA can enhance the ion conduction efficiency between the catalyst,carbon membrane,electrolyte.As a consequence,the specific capacitance of the electrode reaches 973 F·g^(−1)under 1 A·g^(−1),the energy density achieves 32.5 Wh·kg^(−1)with a power density of 266.9 W·kg^(−1),with impressive electrochemical stability that Coulomb efficiency of the electrode remains about 100%after 5000 cycles.Furthermore,in-situ Fourier transformation infrared(FT-IR)analyzes the structure evolvement of the material during synthesis and finds that the annealing process of the material removes a great number of oxygen-containing groups of CA and CDs,generating oxygen vacancies,defects,thus active sites,which enhance the capacitance of the material.展开更多
Due to the poor Fenton reactivity,single-atom Mn-based materials are generally identified as one of the most promising active catalysts for oxygen reduction reaction(ORR).Regulating the electronic density and coordina...Due to the poor Fenton reactivity,single-atom Mn-based materials are generally identified as one of the most promising active catalysts for oxygen reduction reaction(ORR).Regulating the electronic density and coordination environment of atomically dispersed Mn centers is an effective strategy to enhance ORR activity of Mn-based materials.By introducing Zn sites,atomically dispersed Mn centers with multitudes of coordination(including Zn/Mn–Nx and Mn–Nx moieties)can be constructed to form Mn-based ORR catalyst(Zn/Mn-NC)with dual-atom sites.Around Mn–Nx sites,the Zn atoms can effectively modulate the electronic structure and coordination state of Mn centers in Zn/Mn-NC through d–d orbital coupling.The electronic interaction between Zn and Mn sites improves ORR activity,thereby optimizing the oxygen adsorption energy of Mn sites in Zn/Mn-NC and reducing the overall energy barrier.Zn/Mn-NC displays higher ORR half-wave potential than Pt/C(0.89 V vs 0.86 V).The quasi-solid-state zinc-air battery(ZAB)with Zn/Mn-NC as the cathode displayed excellent rechargeability,recyclability,and mechanical robustness.The strategy presented regulates the electronic density and coordination environment of singleatom Mn-based ORR catalysts in quasi-solid-state ZABs.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.22178148,22278193,22075113)the Jiangsu Province and Education Ministry Co-Sponsored Synergistic Innovation Center of Modern Agricultural Equipment(Grant No.XTCX2029)+1 种基金a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_3691)。
文摘Owing to the distinctive structural characteristics,vanadium nitride(VN)is highly regarded as a catalyst for oxygen reduction reaction(ORR)in zinc-air batteries(ZABs).However,VN exhibits limited intrinsic ORR activity due to the weak adsorption ability to O-containing species.Here,the S-doped VN anchored on N,S-doped multi-dimensional carbon(S-VN/Co/NS-MC)was constructed using the solvothermal and in-situ doping methods.Incorporating sulfur atoms into VN species alters the electron spin state of vanadium in the S-VN/Co/NS-MC for regulating the adsorption energy of vanadium sites to oxygen molecules.The introduced sulfur atoms polarize the V 3d_(z)^(2) electrons,shifting spin-down electrons closer to the Fermi level in the S-VN/Co/NS-MC.Consequently,the introduction of sulfur atoms into VN species enhances the adsorption energy of vanadium sites for oxygen molecules.The*OOH dissociation transitions from being unspontaneous on the VN surface to a spontaneous state on the S-doped VN surface.Then,the ORR barrier on the S-VN/Co/NS-MC surface is reduced.The S-VN/Co/NS-MC demonstrates a higher half-wave potential and limiting current density compared to the VN/Co/N-MC.The S-VN/Co/NS-MC-based liquid ZABs display a power density of 195.7 m W cm^(-2),a specific capacity of 815.7 m A h g^(-1),and a cycling stability exceeding 250 h.The S-VN/Co/NS-MC-based flexible ZABs are successfully employed to charge both a smart watch and a mobile phone.This approach holds promise for advancing the commercial utilization of VN-based catalysts in ZABs.
基金financially supported by the National Natural Science Foundation of China(Key Program: 52034011,51974219General Program: 51974219)。
文摘Molybdenum trioxide(MoO_(3))has recently attracted wide attention as a typical conversion-type anode of Li-ion batteries(LIBs).Nevertheless,the inferior intrinsic conductivity and rapid capacity fading during charge/discharge process seriously limit large-scale commercial application of MoO_(3).Herein,the density function theory(DFT)calculations show that electron-proton co-doping preferentially bonds symmetric oxygen to form unstable HxMoO_(3).When the-OH-group in HxMoO_(3) is released into the solution in the form of H_(2)O,it is going to form MoO_(3-x)with lower binding energy.By the means of both electron-proton co-doping and high-energy nanosizing,oxygen vacancies and nanoflower structure are introduced into MoO_(3) to accelerate the ion and electronic diffusion/transport kinetics.Benefitting from the promotion of ion diffusion kinetics related to nanostructures,as well as both the augmentation of active sites and the improvement of electrical conductivity induced by oxygen vacancies,the MoO_(3-x)/nanoflower structures show excellent lithium-ion storage performance.The prepared specimen has a high lithium-ion storage capacity of 1261 mA h g^(-1)at 0.1 A g^(-1)and cyclic stability(450 cycle),remarkably higher than those of previously reported MoO_(3)-based anode materials.
基金This work was supported by the National Science Foundation of China(51772152,51702129,51572114,51972150,21908110,and 51902161)Fundamental Research Funds for the Central Universities(30919011269,30919011110,and 1191030558)+3 种基金Y.W.thanks the Key University Science Research Project of Jiangsu province(16KJB430009)Y.Z.thanks for the support from the Postdoctoral Science Foundation(2018M630527)China Scholarship Council(201708320150)J.S.thanks the Natural Science Foundation of Jiangsu Province(BK20190479,1192261031693).
文摘Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation efficiency,remain as the bottleneck to achieve highly efficient hydrogen evolution.Here,a hollow oxygen-incorporated g-C3N4 nanosheet(OCN)with an improved surface area of 148.5 m2 g^−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere,wherein the C–O bonds are formed through two ways of physical adsorption and doping.The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects,leading to the formation of hollow morphology,while the O-doping results in reduced band gap of g-C3N4.The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6μmol g^−1 h^−1 for~20 h,which is over four times higher than that of g-C3N4(850.1μmol g^−1 h^−1)and outperforms most of the reported g-C3N4 catalysts.
基金This work was financially supported by the National Natural Science Foundation of China (No.50572005)the National Science Fund for Distinguished Young Scholars (No.50325209), and "863" Program (No.2006AA03Z351).
文摘The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope （TEM）, and X-ray diffraction （XRD）. The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vo1% at the center and 6.77vo1% at the surface of the casting thin strip, in vermicular and hand shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3, Cr2O3, and FeO or their multiplicity oxides of MnO.Al2O3, 2FeO.SiO2, and 2MnO.SiO2. Many defects including dislocations and stacking faults have also formed during the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.
基金supported by the National Natural Science Foundation of China(Nos.12271385,12471066)the Shaanxi Fundamental Science Research Project for Mathematics and Physics(No.23JSY027)。
文摘By constructing counterexamples,the authors show that the fixed subgroups are not compressed in direct products of free and surface groups,and hence negate a conjecture in[Zhang,Q.,Ventura,E.and J.Wu,Fixed subgroups are compressed in surface groups,Internat.J.Algebra Comput.,25,2015,865–887].
基金the National Natural Science Foundation of China(Nos.52072152 and 51802126)the Jiangsu University Jinshan Professor Fund and the Jiangsu Specially-Appointed Professor FundOpen Fund from Guangxi Key Laboratory of Electrochemical Energy Materials.
文摘The microstructure design of electrode material is a crucial point to optimize the supercapacitor’s electrochemical properties.In this work,a Bi-based nanocomposite with a three-layer structure(Bi–Bi_(2)O_(3)@carbon armour(CA)/carbon dots(CDs))is synthesized and investigated.This material inherits high capacitance and high activity from bismuth-based materials,the coated CA protects the structure from complete oxidization and improves surface hydrophilicity.Furthermore,CDs in CA can enhance the ion conduction efficiency between the catalyst,carbon membrane,electrolyte.As a consequence,the specific capacitance of the electrode reaches 973 F·g^(−1)under 1 A·g^(−1),the energy density achieves 32.5 Wh·kg^(−1)with a power density of 266.9 W·kg^(−1),with impressive electrochemical stability that Coulomb efficiency of the electrode remains about 100%after 5000 cycles.Furthermore,in-situ Fourier transformation infrared(FT-IR)analyzes the structure evolvement of the material during synthesis and finds that the annealing process of the material removes a great number of oxygen-containing groups of CA and CDs,generating oxygen vacancies,defects,thus active sites,which enhance the capacitance of the material.
基金support of the National Natural Science Foundation of China(grant nos.22278193 and 22178148)Jiangsu Province and Education Ministry Cosponsored Synergistic Innovation Center of Modern Agricultural Equipment(grant no.XTCX2029)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Due to the poor Fenton reactivity,single-atom Mn-based materials are generally identified as one of the most promising active catalysts for oxygen reduction reaction(ORR).Regulating the electronic density and coordination environment of atomically dispersed Mn centers is an effective strategy to enhance ORR activity of Mn-based materials.By introducing Zn sites,atomically dispersed Mn centers with multitudes of coordination(including Zn/Mn–Nx and Mn–Nx moieties)can be constructed to form Mn-based ORR catalyst(Zn/Mn-NC)with dual-atom sites.Around Mn–Nx sites,the Zn atoms can effectively modulate the electronic structure and coordination state of Mn centers in Zn/Mn-NC through d–d orbital coupling.The electronic interaction between Zn and Mn sites improves ORR activity,thereby optimizing the oxygen adsorption energy of Mn sites in Zn/Mn-NC and reducing the overall energy barrier.Zn/Mn-NC displays higher ORR half-wave potential than Pt/C(0.89 V vs 0.86 V).The quasi-solid-state zinc-air battery(ZAB)with Zn/Mn-NC as the cathode displayed excellent rechargeability,recyclability,and mechanical robustness.The strategy presented regulates the electronic density and coordination environment of singleatom Mn-based ORR catalysts in quasi-solid-state ZABs.
