The development of low-cost semiconductor photocatalysts for highly efficient and durable photocatalytic H2 evolution under visible light is very challenging.In this study,we combine low-cost metallic Ni3C cocatalysts...The development of low-cost semiconductor photocatalysts for highly efficient and durable photocatalytic H2 evolution under visible light is very challenging.In this study,we combine low-cost metallic Ni3C cocatalysts with twin nanocrystal Zn0.5Cd0.5S(ZCS)solid solution homojunctions for an efficient visible-light-driven H2 production by a simple approach.As-synthesized Zn0.5Cd0.5S-1%Ni3C(ZCS-1)heterojunction/homojunction nanohybrid exhibited the highest photocatalytic H2-evolution rate of 783μmol h‒1 under visible light,which is 2.88 times higher than that of pristine twin nanocrystal ZCS solid solution.The apparent quantum efficiencies of ZCS and ZCS-1 are measured to be 6.13%and 19.25%at 420 nm,respectively.Specifically,the homojunctions between the zinc blende and wurtzite segments in twin nanocrystal ZCS solid solution can significantly improve the light absorption and separation of photogenerated electron-hole pairs.Furthermore,the heterojunction between ZCS and metallic Ni3C NP cocatalysts can efficiently trap excited electrons from ZCS solid solution and enhance the H2-evolution kinetics at the surface for improving catalytic activity.This study demonstrates a unique one-step strategy for constructing heterojunction/homojunction hybrid nanostructures for a more efficient photocatalytic H2 evolution compared to other noble metal photocatalytic systems.展开更多
The rational construction of a high-efficiency stepscheme heterojunctions is an effective strategy to accelerate the photocatalytic H_(2).Unfortunately,the variant energy-level matching between two different semicondu...The rational construction of a high-efficiency stepscheme heterojunctions is an effective strategy to accelerate the photocatalytic H_(2).Unfortunately,the variant energy-level matching between two different semiconductor confers limited the photocatalytic performance.Herein,a newfangled graphitic-carbon nitride(g-C_(3)N_(4))based isotype step-scheme heterojunction,which consists of sulfur-doped and defective active sites in one microstructural unit,is successfully developed by in-situ polymerizing N,N-dimethylformamide(DMF)and urea,accompanied by sulfur(S)powder.Therein,the polymerization between the amino groups of DMF and the amide group of urea endows the formation of rich defects.The propulsive integration of S-dopants contributes to the excellent fluffiness and dispersibility of lamellar g-C_(3)N_(4).Moreover,the developed heterojunction exhibits a significantly enlarged surface area,thus leading to the more exposed catalytically active sites.Most importantly,the simultaneous introduction of S-doping and defects in the units of g-C_(3)N_(4) also results in a significant improvement in the separation,transfer and recombination efficiency of photo-excited electron-hole pairs.Therefore,the resulting isotype step-scheme heterojunction possesses a superior photocatalytic H_(2) evolution activity in comparison with pristine g-C_(3)N_(4).The newly afforded metal-free isotype step-scheme heterojunction in this work will supply a new insight into coupling strategies of heteroatoms doping and defect engineering for various photocatalytic systems.展开更多
To address the capacity degradation,voltage fading,structural instability and adverse interface reactions in cathode materi-als of lithium-ion batteries(LIBs),numerous modification strategies have been developed,mainl...To address the capacity degradation,voltage fading,structural instability and adverse interface reactions in cathode materi-als of lithium-ion batteries(LIBs),numerous modification strategies have been developed,mainly including coating and doping.In particular,the important strategy of doping(surface doping and bulk doping)has been considered an effective strategy to modulate the crystal lattice structure of cathode materials.However,special insights into the mechanisms and effectiveness of the doping strategy,especially comparisons between surface doping and bulk doping in cathode materials,are still lacking.In this review,recent significant progress in surface doping and bulk doping strategies is demonstrated in detail by focusing on their inherent differences as well as effects on the structural stability,lithium-ion(Li-ion)diffusion and electrochemical properties of cathode materials from the following mechanistic insights:preventing the exposure of reactive Ni on the surface,stabilizing the Li slabs,mitigating the migration of transition metal(TM)ions,alleviating unde-sired structural transformations and adverse interface issues,enlarging the Li interslab spacing,forming three-dimensional(3D)Li-ion diffusion channels,and providing more active sites for the charge-transfer process.Moreover,insights into the correlation between the mechanisms of hybrid surface engineering strategies(doping and coating)and their influences on the electrochemical performance of cathode materials are provided by emphasizing the stabilization of the Li slabs,the enhancement of the surface chemical stability,and the alleviation of TM ion migration.Furthermore,the existing challenges and future perspectives in this promising field are indicated.展开更多
S-scheme heterojunction photocatalysts have been the“stars”in the field of photocatalysis.Herein,a novel S-scheme heterojunction of Ta_(3)N_(5)/BiOCl with oxygen vacancies(OVs)was fabricated via a facile method.The ...S-scheme heterojunction photocatalysts have been the“stars”in the field of photocatalysis.Herein,a novel S-scheme heterojunction of Ta_(3)N_(5)/BiOCl with oxygen vacancies(OVs)was fabricated via a facile method.The charge separation and transport mechanism of this Ta_(3)N_(5)/BiOCl S-scheme heterojunction was verified by the analyses of band energy structures,active species,photoelectric behaviors and DFT theoretical calculation.Compared with Ta_(3)N_(5)and BiOCl,the Ta_(3)N_(5)/BiOCl unveils substantially upgraded photocatalytic property under visible light,and the photocatalytic efficiency for removal of tetracycline(TC)and hexavalent chromium(Cr(VI))reaches 89.6%and 91.6%,respectively.The substantial enhancement of the photocatalytic activity is attributed to the synergistic effect of the S-scheme hetero-structure and oxygen vacancies,which improves the visible-light absorption,while promoting the spatial separation of charge carriers with the optimum redox capacity,thereby boosting the production of active species for catalytic reactions.The TC degradation pathway is deduced and the toxicity evolution of TC is appraised using the QSAR method.In a nutshell,this work gives a deep understanding of the photocatalytic mechanism based on Ta_(3)N_(5)/BiOCl as well as presents a newfangled thought for developing highly efficient S-scheme heterojunction photocatalysts for water decontamination.展开更多
In this work,an amorphous ZnO was coated on LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)using a sol-gel strategy method.The NCM coated with 1 wt.%Zn O and a thickness of about 3 nm exhibits an improved cycling performance,acc...In this work,an amorphous ZnO was coated on LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)using a sol-gel strategy method.The NCM coated with 1 wt.%Zn O and a thickness of about 3 nm exhibits an improved cycling performance,accompanied by a lower capacity fading(from 194.8 to 133.8 m Ah g^(-1),i.e.,68%)than that of the pristine one(i.e.,only 34%)after 300 cycles at 0.2 C.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)indicate that the Zn O coating can improve extraction/insertion of Li+and inhibit the increase in impedance of the NCM cathode material.This approach may benefit the performance improvement of the Ni-rich cathode materials in Lithium-ion batteries(LIBs).展开更多
Inspired by MXene nanosheets and their regulation of surface functional groups,a series of Ti_(2)C‐based single‐atom electrocatalysts(TM@Ti_(2)CT_(x),TM=V,Cr,Mn,Fe,Co,and Ni)with two dif‐ferent functional groups(T=...Inspired by MXene nanosheets and their regulation of surface functional groups,a series of Ti_(2)C‐based single‐atom electrocatalysts(TM@Ti_(2)CT_(x),TM=V,Cr,Mn,Fe,Co,and Ni)with two dif‐ferent functional groups(T=–O and–S)was designed.The CO_(2)RR catalytic performance was stud‐ied using well‐defined ab initio calculations.Our results show that the CO_(2) molecule can be more readily activated on TM@Ti_(2)CO_(2) than the TM@Ti_(2)CS_(2) surface.Bader charge analysis reveals that the Ti_(2)CO_(2) substrate is involved in the adsorption reaction,and enough electrons are injected into the 2π*u orbital of CO_(2),leading to a V‐shaped CO_(2) molecular configuration and partial negative charge distribution.The V‐shaped CO_(2) further reduces the difficulty of the first hydrogenation reac‐tion step.The calculatedΔG of the first hydrogenation reaction on TM@Ti_(2)CO_(2) was significantly lower than that of the TM@Ti_(2)CS_(2) counterpart.However,the subsequent CO_(2) reduction pathways show that the UL of the potential determining step on TM@Ti_(2)CS_(2) is smaller than that of TM@Ti_(2)CO_(2).Combining the advantages of both TM@Ti_(2)CS_(2) and TM@Ti_(2)CO_(2),we designed a mixed functional group surface with–O and–S to anchor TM atoms.The results show that Cr atoms an‐chored on the surface of mixed functional groups exhibit high catalytic activity for the selective production of CH4.This study opens an exciting new avenue for the rational design of highly selec‐tive MXene‐based single‐atom CO_(2)RR electrocatalysts.展开更多
Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions.However,the rapid bulk recombination of photoexcited...Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions.However,the rapid bulk recombination of photoexcited carrier pairs is a fundamental disadvantage.To resolve this problem,we synthesized a dual cocatalysts system of cobalt phosphide(Co P)and molybdenum carbide(Mo_(2)C)embedded on strontium titanate(Sr TiO_(3))nanofibers.Compared with those of pristine SrTiO_(3) and binary samples,the dual cocatalysts system(denoted SCM)showed a significant improvement in the hydrogen evolution and CO_(2) reduction performance.Further,the structure of SCM effectively promoted spatial charge separation and enhanced the photocatalytic performance.In addition,the Schottky junction formed between the SrTiO_(3) and cocatalysts enabled the rapid transfer of photoexcited electrons from SrTiO_(3) to the cocatalysts,resulting in effective separation and prolonged photoexcited electron lifetimes.The electron migration route between SrTiO_(3) and the cocatalysts was determined by in situ irradiation X-ray spectroscopy,and band structures of Sr TiO_(3) and the cocatalysts are proposed based on results obtained from UV-vis diffraction reflection spectroscopy and ultraviolet photoelectron spectroscopy measurements.On the basis of our results,the dual cocatalysts unambiguously boosts charge separation and enhances photocatalytic performance.In summary,we have investigated the flux of photoexcited electrons in a dual cocatalysts system and provided a theoretical basis and ideas for subsequent research.展开更多
In this work, the catalytic activities of MoC-MXene for the co-synthesis of urea from Nand COare reported by well-defined density functional theory(DFT) method. The calculated results show that the presence of surface...In this work, the catalytic activities of MoC-MXene for the co-synthesis of urea from Nand COare reported by well-defined density functional theory(DFT) method. The calculated results show that the presence of surface functional groups is not conducive to the CO/N(C/N) coupling process in urea synthesis reaction. The exposed MoC on the surface can realize urea synthesis at the limit point of 0.69 eV, but the large transition state energy barrier(1.50 eV)indicates that bare MoC is not a promising urea catalyst. Loading single atoms can improve the urea synthesis performance of bare MoC. The energy barrier of urea synthesis reaction and the transition state energy barrier of C/N coupling reaction have dropped significantly by the atomic loading of Fe and Ti on bare MoC. Moreover, Ti doped MoC exhibits better catalytic selectivity toward urea production, making it an excellent catalyst for urea synthesis. We hope this work can pave the way for the electrochemical synthesis of urea.展开更多
The recombination of photogenerated electrons and holes is a crucial factor limiting photocatalytic H_(2)evolution.The S-scheme ZnWO_(4)-ZnIn_(2)S_(4)heterojunction with 2D coupling interfaces was successfully synthes...The recombination of photogenerated electrons and holes is a crucial factor limiting photocatalytic H_(2)evolution.The S-scheme ZnWO_(4)-ZnIn_(2)S_(4)heterojunction with 2D coupling interfaces was successfully synthesized using a simple solvothermal method.An effective S-scheme interfacial charge migration route at the S-scheme heterogeneous interface was determined by energy band structure analyses(such as UPS,Mott-Schottky and XPS plots),which facilitates the separation of photoexcited carriers.It is worth noting that the optimal ZnWO_(4)-ZnIn_(2)S_(4)composite has an H_(2)evolution activity of 4925.3μmol g^(-1)h^(-1)with favourable photostability and stability.Meanwhile,the ZnWO_(4)-Zn In_(2)S_(4)heterojunction exhibits the maximum optical response value(2.8 m A cm-2)in the initial stage,effectively promoting the separation and migration of photogenerated carriers.The establishment of the built-in electric field direction at the interface can effectively promote the space charge separation between the ZnWO_(4)and ZnIn_(2)S_(4)nanosheets,which is favorable to the photocatalytic H_(2)evolution.This work provides valuable guidance for designing S-scheme heterojunction photocatalysts composed of two n-type semiconductors for energy and environmental applications.The recombination of photogenerated electrons and holes is a crucial factor limiting photocatalytic H_(2)evolution.The S-scheme ZnWO_(4)-ZnIn_(2)S_(4)heterojunction with 2D coupling interfaces was successfully synthesized using a simple solvothermal method.An effective S-scheme interfacial charge migration route at the S-scheme heterogeneous interface was determined by energy band structure analyses(such as UPS,Mott-Schottky and XPS plots),which facilitates the separation of photoexcited carriers.It is worth noting that the optimal ZnWO_(4)-ZnIn_(2)S_(4)composite has an H_(2)evolution activity of 4925.3μmol g^(-1)h^(-1)with favourable photostability and stability.Meanwhile,the ZnWO_(4)-ZnIn_(2)S_(4)heterojunction exhibits the maximum optical response val展开更多
Lithium(Li)metal is widely considered the ultimate anode for future rechargeable batteries.However,dendritic growth and related parasitic reactions during long-term cycling often lead to severe safety hazards and cata...Lithium(Li)metal is widely considered the ultimate anode for future rechargeable batteries.However,dendritic growth and related parasitic reactions during long-term cycling often lead to severe safety hazards and catastrophic failure.Herein,we fabricate a hybrid anode by coating single-phase Li_(21)Si_(5)on lithium metal.The resultant electrodes show a stable cycle and depressed polarization in symmetric and half cells.A planar plating/stripping behavior is observed on the modified anode.The investigation of the interplay of Li and Li_(21)Si_(5)shows relatively large adsorption energy in the Li-Si system.The deposition and stripping are surface processes,and Li_(21)Si_(5)maintains its intrinsic phase structure.The deposited Li layer around Li_(21)Si_(5)also has the advantage of diminished preferred orientation,which also contributes to the planar growth of Li.Both LiFePO4(LFP)and LiNi1/3Co1/3 Mn1/3O2(NCM)cathodes were applied to further demonstrate the enhanced rate and cycle performance.展开更多
In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studie...In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studied.It was confirmed that crystallites are inaccessible for water,and therefore water molecules can interact only with polar groups in noncrystalline(amorphous)domains of biopolymers.The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes,which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities.The method of contributions of polar groups to sorption of water molecules was used,which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms.The wetting of biopolymers with water was accompanied by a high exothermic thermal effect,in direct proportion to the amorphicity degree.The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated,which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.展开更多
In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphat...In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphatic acids.The specific gravity of the highly substituted samples was measured by a pycnometric method in the aqueous medium.To calculate the molar,Van der Waals,and free volumes,as well as the packing coefficient of amorphous esters the method of additive contributions of partial volumes of atoms and atom groups in the volumes of polymers was used.Based on the molar volume,also specific gravity of cellulose esters was calculated.The coincidence of calculated and experimental characteristics was shown.In addition,the relationship between glass transition temperature and free volume was found for the esters.The theoretical equations were derived,which provide predicting the structural characteristics of cellulose esters with different degrees of substitution.展开更多
In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,a...In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,at the various ratios of the solvent to cellulose(v/w)(R).If was found that after treatment of cellulose materials with the solvent at R≥5,a completely amorphous cellulose(AC)is formed.Due to high digestibility,the AC with concentration of 50 g/L is converted to glucose almost completely for 48 h under the action of cellulolytic enzyme CTec-3 with a dose of 30 mg/g solid sample.Such sample can be used as an amorphous standard in the study of crystallinity degree and enzymatic hydrolysis of various types of cellulose and lignocellulose.It was found that enzymatic saccharification is most advantageous to carry out at elevated concentrations of AC,150 g/L.Due to high cost of MCC,it is preferable to use a cheap cellulose raw material,such as mixed waste paper(MWP),for the commercial production of AC and glucose.The resulting glucose can find application in biotechnology as a promising nutrient for various microorganisms.展开更多
文摘The development of low-cost semiconductor photocatalysts for highly efficient and durable photocatalytic H2 evolution under visible light is very challenging.In this study,we combine low-cost metallic Ni3C cocatalysts with twin nanocrystal Zn0.5Cd0.5S(ZCS)solid solution homojunctions for an efficient visible-light-driven H2 production by a simple approach.As-synthesized Zn0.5Cd0.5S-1%Ni3C(ZCS-1)heterojunction/homojunction nanohybrid exhibited the highest photocatalytic H2-evolution rate of 783μmol h‒1 under visible light,which is 2.88 times higher than that of pristine twin nanocrystal ZCS solid solution.The apparent quantum efficiencies of ZCS and ZCS-1 are measured to be 6.13%and 19.25%at 420 nm,respectively.Specifically,the homojunctions between the zinc blende and wurtzite segments in twin nanocrystal ZCS solid solution can significantly improve the light absorption and separation of photogenerated electron-hole pairs.Furthermore,the heterojunction between ZCS and metallic Ni3C NP cocatalysts can efficiently trap excited electrons from ZCS solid solution and enhance the H2-evolution kinetics at the surface for improving catalytic activity.This study demonstrates a unique one-step strategy for constructing heterojunction/homojunction hybrid nanostructures for a more efficient photocatalytic H2 evolution compared to other noble metal photocatalytic systems.
基金This work was supported by the National Natural Science Foundation of China(No.62004143)the Central Government Guided Local Science and Technology Development Special Fund Project(No.2020ZYYD033)+4 种基金the Natural Science Foundation of Hubei Province(No.2021CFB133)the Opening Fund of Key Laboratory of Rare Mineral Ministry of Natural Resources(No.KLRM-KF 202005)the Open Research Fund of Key Laboratory of Material Chemistry for Energy Conversion and Storage(HUST),Ministry of Education(No.2021JYBKF05)the Opening Fund of Key Laboratory for Green Chemical Process of Ministry of Education of Wuhan Institute of Technology(No.GCP202101)the Innovation Project of Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education(No.LCX2021003)。
文摘The rational construction of a high-efficiency stepscheme heterojunctions is an effective strategy to accelerate the photocatalytic H_(2).Unfortunately,the variant energy-level matching between two different semiconductor confers limited the photocatalytic performance.Herein,a newfangled graphitic-carbon nitride(g-C_(3)N_(4))based isotype step-scheme heterojunction,which consists of sulfur-doped and defective active sites in one microstructural unit,is successfully developed by in-situ polymerizing N,N-dimethylformamide(DMF)and urea,accompanied by sulfur(S)powder.Therein,the polymerization between the amino groups of DMF and the amide group of urea endows the formation of rich defects.The propulsive integration of S-dopants contributes to the excellent fluffiness and dispersibility of lamellar g-C_(3)N_(4).Moreover,the developed heterojunction exhibits a significantly enlarged surface area,thus leading to the more exposed catalytically active sites.Most importantly,the simultaneous introduction of S-doping and defects in the units of g-C_(3)N_(4) also results in a significant improvement in the separation,transfer and recombination efficiency of photo-excited electron-hole pairs.Therefore,the resulting isotype step-scheme heterojunction possesses a superior photocatalytic H_(2) evolution activity in comparison with pristine g-C_(3)N_(4).The newly afforded metal-free isotype step-scheme heterojunction in this work will supply a new insight into coupling strategies of heteroatoms doping and defect engineering for various photocatalytic systems.
基金the National Natural Science Foundation of China(52072298 and 51802261)the Local Special Service Program Funded by Education Department of Shaanxi Provincial Government(19JC031)+2 种基金the Natural Science Foundation of Shaanxi(2020JC-41,2021TD-15)the Xi’an Science and Technology Project of China(2019219714SYS012CG034)the Project 2019JLP-04 supported by the Joint Foundation of Shaanxi.
文摘To address the capacity degradation,voltage fading,structural instability and adverse interface reactions in cathode materi-als of lithium-ion batteries(LIBs),numerous modification strategies have been developed,mainly including coating and doping.In particular,the important strategy of doping(surface doping and bulk doping)has been considered an effective strategy to modulate the crystal lattice structure of cathode materials.However,special insights into the mechanisms and effectiveness of the doping strategy,especially comparisons between surface doping and bulk doping in cathode materials,are still lacking.In this review,recent significant progress in surface doping and bulk doping strategies is demonstrated in detail by focusing on their inherent differences as well as effects on the structural stability,lithium-ion(Li-ion)diffusion and electrochemical properties of cathode materials from the following mechanistic insights:preventing the exposure of reactive Ni on the surface,stabilizing the Li slabs,mitigating the migration of transition metal(TM)ions,alleviating unde-sired structural transformations and adverse interface issues,enlarging the Li interslab spacing,forming three-dimensional(3D)Li-ion diffusion channels,and providing more active sites for the charge-transfer process.Moreover,insights into the correlation between the mechanisms of hybrid surface engineering strategies(doping and coating)and their influences on the electrochemical performance of cathode materials are provided by emphasizing the stabilization of the Li slabs,the enhancement of the surface chemical stability,and the alleviation of TM ion migration.Furthermore,the existing challenges and future perspectives in this promising field are indicated.
基金financially supported by the Natural Science Foundation of Zhejiang Province(No.LY20E080014)the National Natural Science Foundation of China(No.51708504)+1 种基金National Natural Science Foundation of China(No.21975084)the Science and Technology Project of Zhoushan City(No.2020C21009 and 2022C41011)。
文摘S-scheme heterojunction photocatalysts have been the“stars”in the field of photocatalysis.Herein,a novel S-scheme heterojunction of Ta_(3)N_(5)/BiOCl with oxygen vacancies(OVs)was fabricated via a facile method.The charge separation and transport mechanism of this Ta_(3)N_(5)/BiOCl S-scheme heterojunction was verified by the analyses of band energy structures,active species,photoelectric behaviors and DFT theoretical calculation.Compared with Ta_(3)N_(5)and BiOCl,the Ta_(3)N_(5)/BiOCl unveils substantially upgraded photocatalytic property under visible light,and the photocatalytic efficiency for removal of tetracycline(TC)and hexavalent chromium(Cr(VI))reaches 89.6%and 91.6%,respectively.The substantial enhancement of the photocatalytic activity is attributed to the synergistic effect of the S-scheme hetero-structure and oxygen vacancies,which improves the visible-light absorption,while promoting the spatial separation of charge carriers with the optimum redox capacity,thereby boosting the production of active species for catalytic reactions.The TC degradation pathway is deduced and the toxicity evolution of TC is appraised using the QSAR method.In a nutshell,this work gives a deep understanding of the photocatalytic mechanism based on Ta_(3)N_(5)/BiOCl as well as presents a newfangled thought for developing highly efficient S-scheme heterojunction photocatalysts for water decontamination.
基金supported by the Natural Science Basic Research Plan in Shaanxi Province of China(2019JLP-04)the National Natural Science Foundation of China(51672189)+1 种基金Xi’an Science and Technology Project of China(201805037YD15CG21(20))Tianjin Science and Technology Project(18PTZWHZ00020)
文摘In this work,an amorphous ZnO was coated on LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)using a sol-gel strategy method.The NCM coated with 1 wt.%Zn O and a thickness of about 3 nm exhibits an improved cycling performance,accompanied by a lower capacity fading(from 194.8 to 133.8 m Ah g^(-1),i.e.,68%)than that of the pristine one(i.e.,only 34%)after 300 cycles at 0.2 C.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)indicate that the Zn O coating can improve extraction/insertion of Li+and inhibit the increase in impedance of the NCM cathode material.This approach may benefit the performance improvement of the Ni-rich cathode materials in Lithium-ion batteries(LIBs).
文摘Inspired by MXene nanosheets and their regulation of surface functional groups,a series of Ti_(2)C‐based single‐atom electrocatalysts(TM@Ti_(2)CT_(x),TM=V,Cr,Mn,Fe,Co,and Ni)with two dif‐ferent functional groups(T=–O and–S)was designed.The CO_(2)RR catalytic performance was stud‐ied using well‐defined ab initio calculations.Our results show that the CO_(2) molecule can be more readily activated on TM@Ti_(2)CO_(2) than the TM@Ti_(2)CS_(2) surface.Bader charge analysis reveals that the Ti_(2)CO_(2) substrate is involved in the adsorption reaction,and enough electrons are injected into the 2π*u orbital of CO_(2),leading to a V‐shaped CO_(2) molecular configuration and partial negative charge distribution.The V‐shaped CO_(2) further reduces the difficulty of the first hydrogenation reac‐tion step.The calculatedΔG of the first hydrogenation reaction on TM@Ti_(2)CO_(2) was significantly lower than that of the TM@Ti_(2)CS_(2) counterpart.However,the subsequent CO_(2) reduction pathways show that the UL of the potential determining step on TM@Ti_(2)CS_(2) is smaller than that of TM@Ti_(2)CO_(2).Combining the advantages of both TM@Ti_(2)CS_(2) and TM@Ti_(2)CO_(2),we designed a mixed functional group surface with–O and–S to anchor TM atoms.The results show that Cr atoms an‐chored on the surface of mixed functional groups exhibit high catalytic activity for the selective production of CH4.This study opens an exciting new avenue for the rational design of highly selec‐tive MXene‐based single‐atom CO_(2)RR electrocatalysts.
文摘Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions.However,the rapid bulk recombination of photoexcited carrier pairs is a fundamental disadvantage.To resolve this problem,we synthesized a dual cocatalysts system of cobalt phosphide(Co P)and molybdenum carbide(Mo_(2)C)embedded on strontium titanate(Sr TiO_(3))nanofibers.Compared with those of pristine SrTiO_(3) and binary samples,the dual cocatalysts system(denoted SCM)showed a significant improvement in the hydrogen evolution and CO_(2) reduction performance.Further,the structure of SCM effectively promoted spatial charge separation and enhanced the photocatalytic performance.In addition,the Schottky junction formed between the SrTiO_(3) and cocatalysts enabled the rapid transfer of photoexcited electrons from SrTiO_(3) to the cocatalysts,resulting in effective separation and prolonged photoexcited electron lifetimes.The electron migration route between SrTiO_(3) and the cocatalysts was determined by in situ irradiation X-ray spectroscopy,and band structures of Sr TiO_(3) and the cocatalysts are proposed based on results obtained from UV-vis diffraction reflection spectroscopy and ultraviolet photoelectron spectroscopy measurements.On the basis of our results,the dual cocatalysts unambiguously boosts charge separation and enhances photocatalytic performance.In summary,we have investigated the flux of photoexcited electrons in a dual cocatalysts system and provided a theoretical basis and ideas for subsequent research.
基金supported by the Natural Science Fund for Distinguished Young Scholars of Hubei Province(No.2020CFA087)Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011303)+3 种基金the Basic Research Program of Shenzhen(No.JCYJ20190809120015163)the Central Government Guides Local Science and Technology Development Funds to Freely Explore Basic Research Projects(No.2021Szvup106)the Overseas Expertise Introduction Project for Discipline Innovation of China(No.B18038)Fundamental Research Funds for the Central Universities of Wuhan University of Technology(No.35401053-2022)。
文摘In this work, the catalytic activities of MoC-MXene for the co-synthesis of urea from Nand COare reported by well-defined density functional theory(DFT) method. The calculated results show that the presence of surface functional groups is not conducive to the CO/N(C/N) coupling process in urea synthesis reaction. The exposed MoC on the surface can realize urea synthesis at the limit point of 0.69 eV, but the large transition state energy barrier(1.50 eV)indicates that bare MoC is not a promising urea catalyst. Loading single atoms can improve the urea synthesis performance of bare MoC. The energy barrier of urea synthesis reaction and the transition state energy barrier of C/N coupling reaction have dropped significantly by the atomic loading of Fe and Ti on bare MoC. Moreover, Ti doped MoC exhibits better catalytic selectivity toward urea production, making it an excellent catalyst for urea synthesis. We hope this work can pave the way for the electrochemical synthesis of urea.
基金financially supported by the framework of the Young Taishan Scholars Program of Shandong Province(No.tsqn.201909026)the Natural Science Foundation of Jiangsu Province(No.BK20200237)+2 种基金the Youth Interdisciplinary Science and Innovative Research Groups of Shandong University(No.2020QNQT014)the Shandong University Future Youth Grant Program(No.61440089964189)the National Natural Science Foundation of China(No.21975084)for their support。
文摘The recombination of photogenerated electrons and holes is a crucial factor limiting photocatalytic H_(2)evolution.The S-scheme ZnWO_(4)-ZnIn_(2)S_(4)heterojunction with 2D coupling interfaces was successfully synthesized using a simple solvothermal method.An effective S-scheme interfacial charge migration route at the S-scheme heterogeneous interface was determined by energy band structure analyses(such as UPS,Mott-Schottky and XPS plots),which facilitates the separation of photoexcited carriers.It is worth noting that the optimal ZnWO_(4)-ZnIn_(2)S_(4)composite has an H_(2)evolution activity of 4925.3μmol g^(-1)h^(-1)with favourable photostability and stability.Meanwhile,the ZnWO_(4)-Zn In_(2)S_(4)heterojunction exhibits the maximum optical response value(2.8 m A cm-2)in the initial stage,effectively promoting the separation and migration of photogenerated carriers.The establishment of the built-in electric field direction at the interface can effectively promote the space charge separation between the ZnWO_(4)and ZnIn_(2)S_(4)nanosheets,which is favorable to the photocatalytic H_(2)evolution.This work provides valuable guidance for designing S-scheme heterojunction photocatalysts composed of two n-type semiconductors for energy and environmental applications.The recombination of photogenerated electrons and holes is a crucial factor limiting photocatalytic H_(2)evolution.The S-scheme ZnWO_(4)-ZnIn_(2)S_(4)heterojunction with 2D coupling interfaces was successfully synthesized using a simple solvothermal method.An effective S-scheme interfacial charge migration route at the S-scheme heterogeneous interface was determined by energy band structure analyses(such as UPS,Mott-Schottky and XPS plots),which facilitates the separation of photoexcited carriers.It is worth noting that the optimal ZnWO_(4)-ZnIn_(2)S_(4)composite has an H_(2)evolution activity of 4925.3μmol g^(-1)h^(-1)with favourable photostability and stability.Meanwhile,the ZnWO_(4)-ZnIn_(2)S_(4)heterojunction exhibits the maximum optical response val
基金the National Natural Science Foundation of China(Nos.51571182 and 51001091)the Fundamental Research Program from the Ministry of Science and Technology of China(No.2014CB931704)+1 种基金the Program for Science&Technology Innovation Talents in Universities of Henan Province(No.18HASTIT009)partially the Provincial Scientific Research Program of Henan(Nos.2017GGJS001 and 172102410023)。
文摘Lithium(Li)metal is widely considered the ultimate anode for future rechargeable batteries.However,dendritic growth and related parasitic reactions during long-term cycling often lead to severe safety hazards and catastrophic failure.Herein,we fabricate a hybrid anode by coating single-phase Li_(21)Si_(5)on lithium metal.The resultant electrodes show a stable cycle and depressed polarization in symmetric and half cells.A planar plating/stripping behavior is observed on the modified anode.The investigation of the interplay of Li and Li_(21)Si_(5)shows relatively large adsorption energy in the Li-Si system.The deposition and stripping are surface processes,and Li_(21)Si_(5)maintains its intrinsic phase structure.The deposited Li layer around Li_(21)Si_(5)also has the advantage of diminished preferred orientation,which also contributes to the planar growth of Li.Both LiFePO4(LFP)and LiNi1/3Co1/3 Mn1/3O2(NCM)cathodes were applied to further demonstrate the enhanced rate and cycle performance.
文摘In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studied.It was confirmed that crystallites are inaccessible for water,and therefore water molecules can interact only with polar groups in noncrystalline(amorphous)domains of biopolymers.The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes,which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities.The method of contributions of polar groups to sorption of water molecules was used,which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms.The wetting of biopolymers with water was accompanied by a high exothermic thermal effect,in direct proportion to the amorphicity degree.The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated,which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.
文摘In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphatic acids.The specific gravity of the highly substituted samples was measured by a pycnometric method in the aqueous medium.To calculate the molar,Van der Waals,and free volumes,as well as the packing coefficient of amorphous esters the method of additive contributions of partial volumes of atoms and atom groups in the volumes of polymers was used.Based on the molar volume,also specific gravity of cellulose esters was calculated.The coincidence of calculated and experimental characteristics was shown.In addition,the relationship between glass transition temperature and free volume was found for the esters.The theoretical equations were derived,which provide predicting the structural characteristics of cellulose esters with different degrees of substitution.
文摘In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,at the various ratios of the solvent to cellulose(v/w)(R).If was found that after treatment of cellulose materials with the solvent at R≥5,a completely amorphous cellulose(AC)is formed.Due to high digestibility,the AC with concentration of 50 g/L is converted to glucose almost completely for 48 h under the action of cellulolytic enzyme CTec-3 with a dose of 30 mg/g solid sample.Such sample can be used as an amorphous standard in the study of crystallinity degree and enzymatic hydrolysis of various types of cellulose and lignocellulose.It was found that enzymatic saccharification is most advantageous to carry out at elevated concentrations of AC,150 g/L.Due to high cost of MCC,it is preferable to use a cheap cellulose raw material,such as mixed waste paper(MWP),for the commercial production of AC and glucose.The resulting glucose can find application in biotechnology as a promising nutrient for various microorganisms.
