Metal-semiconductor ohmic contacts are required to reduce the energy dissipation for two-dimensional (2D) electronic devices, and phase engineering of 2D transition-metal dichalcogenides (TMDCs) is a promising approac...Metal-semiconductor ohmic contacts are required to reduce the energy dissipation for two-dimensional (2D) electronic devices, and phase engineering of 2D transition-metal dichalcogenides (TMDCs) is a promising approach for building ohmic contacts. Here, 2D in-plane 1T′-2H MoTe2 homojunctions were prepared by direct epitaxy via vapor deposition. The interface properties of in-plane 1T′-2H MoTe2 homojunction were investigated in detail by combining experiments, calculations and theories. The ohmic contact properties of 1T′-2H MoTe2 homojunction were proved according to Kelvin force probe microscopy and density functional theory calculations. The charge carriers robust transport in in-plane 1T′-2H MoTe2 homojunction without Fermi-level pinning can be well described by Poisson equation and band alignment. These results indicate that phase engineering of 2D TMDCs is promising to construct ohmic contacts for device applications.展开更多
Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide(MoS_(2)).MoS_(2)-based composites are usually used for the electromagnetic wave(EMW)absorber,but the effect of di...Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide(MoS_(2)).MoS_(2)-based composites are usually used for the electromagnetic wave(EMW)absorber,but the effect of different phases on the EMW absorbing performance,such as 1T and 2H phase,is still not studied.In this work,micro-1T/2H MoS_(2) is achieved via a facile one-step hydrother-mal route,in which the 1T phase is induced by the intercalation of guest molecules and ions.The EMW absorption mechanism of single MoS_(2) is revealed by presenting a comparative study between 1T/2H MoS_(2) and 2H MoS_(2).As a result,1T/2H MoS_(2) with the matrix loading of 15%exhibits excellent microwave absorption property than 2H MoS_(2).Furthermore,taking the advantage of 1T/2H MoS_(2),a flexible EMW absorbers that ultrathin 1T/2H MoS_(2)grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%.This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.展开更多
Photocatalytic hydrogen generation from water-splitting holds huge promise for resolving the current energy shortage and environmental issues.Nevertheless,it is still challenging so far to develop non-noble-metal phot...Photocatalytic hydrogen generation from water-splitting holds huge promise for resolving the current energy shortage and environmental issues.Nevertheless,it is still challenging so far to develop non-noble-metal photocatalysts which are efficient toward solar-powered hydrogen evolution reaction(HER).In this work,through an ultrasonic water-bath strategy combined with solvothermal and electrostatic assembly processes,we obtain homogeneous Cd_(1-x)Zn_(x)S–Ni_(2)P–MoS_(2) hybrid nano-spheres consisting of Cd_(1-x)Zn_(x)S solid solutions decorated by Ni_(2)P and 1 T/2 H MoS_(2) cocatalysts,which demonstrate excellent activity and stability for visible-light-responsive(λ>420 nm)H_(2) production.Specifically,the Cd_(1-x)Zn_(x)S-Ni_(2)P-MoS_(2) nano-spheres with 2 wt%Ni_(2)P and 0.2 wt%MoS_(2)(CZ_(0.7)S–2 N–0.2 M)exhibit the optimal HER activity of 55.77 mmol·g^(-1)·h^(-1),about 47 and 32 times more than that of CZ_(0.7)S and Pt–CZ_(0.7)S,respectively.The outstanding HER performance of Cd_(1-x)Zn_(x)S–Ni_(2)P–MoS_(2) can be ascribed to the presence of abundant HER active sites in Ni2 P nanoparticles and 1 T/2 H MoS_(2) nanosheets as well as the effective transfer and separation of charge carriers.Moreover,the coupling sequence of cocatalysts in Cd_(1-x)Zn_(x)S–Ni_(2)P–MoS_(2) is found to be critical in the regulation of charge transfer pathways and thus the resultant photocatalytic efficiency.The results displayed here could facilitate the engineering of high-performance photocatalysts employing multi-component cocatalysts for sustainable solar-to-fuel conversion.展开更多
Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)na...Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.展开更多
Hydrogen evolution reaction(HER)catalytic electrodes under actual working conditions show interesting mass transfer behaviors at solid(electrode)/liquid(electrolyte)/gas(hydrogen)three-phase interfaces.These behaviors...Hydrogen evolution reaction(HER)catalytic electrodes under actual working conditions show interesting mass transfer behaviors at solid(electrode)/liquid(electrolyte)/gas(hydrogen)three-phase interfaces.These behaviors are essential for forming a continuous and effective physical contact region between the electrolyte and the electrode and require further detailed understanding.Here,a case study on 1 T-2 H phase molybdenum disulfide(Mo S_(2))/carbon fiber paper(CFP)catalytic electrodes is performed.Rapid gas-liquid mass transfer at the interface for enhancing the working area stability and capillarity for increasing the electrode working area is found.The real scenario,wherein the energy utilization efficiency of the as-prepared non-noble metal catalytic electrode exceeds that of the noble metal catalytic electrode,is disclosed.Specifically,a fluid dynamics model is developed to investigate the behavior mechanism of hydrogen bubbles from generation to desorption on the catalytic electrode surface with different hydrophilic and hydrophobic properties.These new insights and theoretical evidence on the non-negligible three-phase interface behaviors will identify opportunities and motivate future research in high-efficiency,stability,and low-cost HER catalytic electrode development.展开更多
Photocatalytic water purification is an efficient environmental protection method that can be used to eliminate toxic and harmful substances from industrial effluents.However,the TiO2-based catalysts currently in use ...Photocatalytic water purification is an efficient environmental protection method that can be used to eliminate toxic and harmful substances from industrial effluents.However,the TiO2-based catalysts currently in use absorb only a small portion of the solar spectrum in the ultraviolet(UV)region,resulting in lower efficiency.In this paper,we demonstrate a molybdenum disulfide/zeolitic imidazolate framework-8(MoS2/ZIF-8)composite photocatalyst that increases the photocatalytic degradation of ciprofloxacin(CIP)and tetracycline hydrochloride(TC)by factors of 1.21 and 1.07,respectively.The transformation products of CIP and TC from the catalysis processes are tentatively identified,with the metal-organic framework(MOF)being considered to be the main active species with holes being considered as the main active species.The hydrogen production rate of the MoS2/ZIF-8 nanocomposites is 1.79 times higher than that of MoS2.This work provides a novel perspective for exploring original and efficient 1T/2H-MoS2/MOF-based photocatalysts by optimizing the construction of surface nano-heterojunction structures.The composite photocatalyst is found to be durable,with its catalytic performance being preserved under stability testing.Thus,1T/2H-MoS2/MOF-based photocatalysts have excellent prospects for practical antibiotic-degradation engineering.展开更多
A new biphenol-like monomer,4,4′-methylenebis[4-(1,4-phenylene)-phthalazin-1(2H)-one] was synthesized from phthalic anhydride and diphenylmethane in two steps.In the first step,Friedel-Crafts reaction was carried out...A new biphenol-like monomer,4,4′-methylenebis[4-(1,4-phenylene)-phthalazin-1(2H)-one] was synthesized from phthalic anhydride and diphenylmethane in two steps.In the first step,Friedel-Crafts reaction was carried out in 1,2-dichloroethane between diphenylmethane and phthalic anhydride.The obtained product was used in the second step with hydrazine monohydrate added into its solution,followed by recrystallization in acetic acid.The melting point showed by differential scanning calorimetry of the bis(phthalazinone) monomer was 338.1℃.The overall yield of the biphenol-like monomer was 60%.A new polyphthalazinone was prepared from 4,4′-difluorodiphenylketone(DFK) and 4,4′-methylenebis[4-(1,4-phenylene)-phthalazin-1(2H)-one] by solution polycondensation in N-methyl-2-pyrrolidone(NMP) with anhydrous K 2CO 3 as a catalyst.High molecular weight polymer was formed in 8 h at 190℃.The polymer was refined by precipitation from its 15% NMP solution with methanol as the precipitating agent.The powder of the polymer was dried in a vacuum oven under 120℃ for 48*!h and then under 200℃ for 4*!h.The intrinsic viscosity of the polymer was 0.58*!dL/g in NMP at 25℃.The polymer showed high glass transition temperature (T g) at 258℃ by DSC.The decomposition temperature for 5% weight loss (T d5) in nitrogen measured by thermogravimetric analysis occurred at 431℃.The solubility of the polymer was investigated at room temperature.The polymer was soluble in NMP,m-cresol and partially soluble in chloroform,and insoluble in N,N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO).The methylene group and bis-(phthalazinone) structure in the backbone of the polymer contribute much to the good solubility,and the rigid structure of bis(phthalazinone) retains its good thermal properties.展开更多
基金This work was supported by the Grants from National Natural Science Foundation of China(No.11874316)Scientific Research Fund of Hunan Provincial Education Department(No.18A059)+2 种基金the Hunan Provincial Innovation Foundation for Postgraduate(No.CX2018B321)the Project of Xiangtan Science and Technology Bureau(No.CXY-ZD20172002)Innovative Research Team in University(No.IRT 17R91).
文摘Metal-semiconductor ohmic contacts are required to reduce the energy dissipation for two-dimensional (2D) electronic devices, and phase engineering of 2D transition-metal dichalcogenides (TMDCs) is a promising approach for building ohmic contacts. Here, 2D in-plane 1T′-2H MoTe2 homojunctions were prepared by direct epitaxy via vapor deposition. The interface properties of in-plane 1T′-2H MoTe2 homojunction were investigated in detail by combining experiments, calculations and theories. The ohmic contact properties of 1T′-2H MoTe2 homojunction were proved according to Kelvin force probe microscopy and density functional theory calculations. The charge carriers robust transport in in-plane 1T′-2H MoTe2 homojunction without Fermi-level pinning can be well described by Poisson equation and band alignment. These results indicate that phase engineering of 2D TMDCs is promising to construct ohmic contacts for device applications.
基金the National Natural Science Foundation of China(No.51672222)Joint Fund Project-Enterprise-Shaanxi Coal Joint Fund Project(2019JLM-32)+2 种基金Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX202054)the Graduate innovation team of Northwestern Polytechnical Universitythe Analysis and Testing Center of Northwestern Polytechnical University for their technical assistance in SEM(Verios G4).
文摘Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide(MoS_(2)).MoS_(2)-based composites are usually used for the electromagnetic wave(EMW)absorber,but the effect of different phases on the EMW absorbing performance,such as 1T and 2H phase,is still not studied.In this work,micro-1T/2H MoS_(2) is achieved via a facile one-step hydrother-mal route,in which the 1T phase is induced by the intercalation of guest molecules and ions.The EMW absorption mechanism of single MoS_(2) is revealed by presenting a comparative study between 1T/2H MoS_(2) and 2H MoS_(2).As a result,1T/2H MoS_(2) with the matrix loading of 15%exhibits excellent microwave absorption property than 2H MoS_(2).Furthermore,taking the advantage of 1T/2H MoS_(2),a flexible EMW absorbers that ultrathin 1T/2H MoS_(2)grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%.This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.
基金supported by the Foundation of State Key Laboratory of Structural Chemistry(20190021)the National Natural Science Foundation of China(51802170,21801150,51772162)+1 种基金the Natural Science Foundation of Shandong Province(ZR2018BEM014,ZR2019JQ14,ZR2019MB001)the Taishan Scholar Project of Shandong Province。
文摘Photocatalytic hydrogen generation from water-splitting holds huge promise for resolving the current energy shortage and environmental issues.Nevertheless,it is still challenging so far to develop non-noble-metal photocatalysts which are efficient toward solar-powered hydrogen evolution reaction(HER).In this work,through an ultrasonic water-bath strategy combined with solvothermal and electrostatic assembly processes,we obtain homogeneous Cd_(1-x)Zn_(x)S–Ni_(2)P–MoS_(2) hybrid nano-spheres consisting of Cd_(1-x)Zn_(x)S solid solutions decorated by Ni_(2)P and 1 T/2 H MoS_(2) cocatalysts,which demonstrate excellent activity and stability for visible-light-responsive(λ>420 nm)H_(2) production.Specifically,the Cd_(1-x)Zn_(x)S-Ni_(2)P-MoS_(2) nano-spheres with 2 wt%Ni_(2)P and 0.2 wt%MoS_(2)(CZ_(0.7)S–2 N–0.2 M)exhibit the optimal HER activity of 55.77 mmol·g^(-1)·h^(-1),about 47 and 32 times more than that of CZ_(0.7)S and Pt–CZ_(0.7)S,respectively.The outstanding HER performance of Cd_(1-x)Zn_(x)S–Ni_(2)P–MoS_(2) can be ascribed to the presence of abundant HER active sites in Ni2 P nanoparticles and 1 T/2 H MoS_(2) nanosheets as well as the effective transfer and separation of charge carriers.Moreover,the coupling sequence of cocatalysts in Cd_(1-x)Zn_(x)S–Ni_(2)P–MoS_(2) is found to be critical in the regulation of charge transfer pathways and thus the resultant photocatalytic efficiency.The results displayed here could facilitate the engineering of high-performance photocatalysts employing multi-component cocatalysts for sustainable solar-to-fuel conversion.
基金National Natural Science Foundation of China,Grant/Award Number:NSFC‐U1904215National Research Foundation of Korea,Grant/Award Number:2021R1A2C2012127。
文摘Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.
基金supported by the National Natural Science Foundation of China(No.62004051)the Natural Science Foundation of Heilongjiang province(No.LH2020F013)+1 种基金the China Postdoctoral Science Fund(No.2020M670909)the Heilongjiang Postdoctoral Science Fund(No.LBH-Z19017)。
文摘Hydrogen evolution reaction(HER)catalytic electrodes under actual working conditions show interesting mass transfer behaviors at solid(electrode)/liquid(electrolyte)/gas(hydrogen)three-phase interfaces.These behaviors are essential for forming a continuous and effective physical contact region between the electrolyte and the electrode and require further detailed understanding.Here,a case study on 1 T-2 H phase molybdenum disulfide(Mo S_(2))/carbon fiber paper(CFP)catalytic electrodes is performed.Rapid gas-liquid mass transfer at the interface for enhancing the working area stability and capillarity for increasing the electrode working area is found.The real scenario,wherein the energy utilization efficiency of the as-prepared non-noble metal catalytic electrode exceeds that of the noble metal catalytic electrode,is disclosed.Specifically,a fluid dynamics model is developed to investigate the behavior mechanism of hydrogen bubbles from generation to desorption on the catalytic electrode surface with different hydrophilic and hydrophobic properties.These new insights and theoretical evidence on the non-negligible three-phase interface behaviors will identify opportunities and motivate future research in high-efficiency,stability,and low-cost HER catalytic electrode development.
基金Dr.Wen-Qian Chen and Miss Lin-Yue Li contributed equally to this work.The authors of this work gratefully acknowledge the financial support provided by the National Natural Science Foundation of China(41573096 and 21707064)the Program for Changjiang Scholars and Innovative Research Teams in University(IRT_17R71)the State Environmental Protection Key Laboratory of Integrated Surface Water–Groundwater Pollution Control,Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control(2017B030301012).
文摘Photocatalytic water purification is an efficient environmental protection method that can be used to eliminate toxic and harmful substances from industrial effluents.However,the TiO2-based catalysts currently in use absorb only a small portion of the solar spectrum in the ultraviolet(UV)region,resulting in lower efficiency.In this paper,we demonstrate a molybdenum disulfide/zeolitic imidazolate framework-8(MoS2/ZIF-8)composite photocatalyst that increases the photocatalytic degradation of ciprofloxacin(CIP)and tetracycline hydrochloride(TC)by factors of 1.21 and 1.07,respectively.The transformation products of CIP and TC from the catalysis processes are tentatively identified,with the metal-organic framework(MOF)being considered to be the main active species with holes being considered as the main active species.The hydrogen production rate of the MoS2/ZIF-8 nanocomposites is 1.79 times higher than that of MoS2.This work provides a novel perspective for exploring original and efficient 1T/2H-MoS2/MOF-based photocatalysts by optimizing the construction of surface nano-heterojunction structures.The composite photocatalyst is found to be durable,with its catalytic performance being preserved under stability testing.Thus,1T/2H-MoS2/MOF-based photocatalysts have excellent prospects for practical antibiotic-degradation engineering.
文摘A new biphenol-like monomer,4,4′-methylenebis[4-(1,4-phenylene)-phthalazin-1(2H)-one] was synthesized from phthalic anhydride and diphenylmethane in two steps.In the first step,Friedel-Crafts reaction was carried out in 1,2-dichloroethane between diphenylmethane and phthalic anhydride.The obtained product was used in the second step with hydrazine monohydrate added into its solution,followed by recrystallization in acetic acid.The melting point showed by differential scanning calorimetry of the bis(phthalazinone) monomer was 338.1℃.The overall yield of the biphenol-like monomer was 60%.A new polyphthalazinone was prepared from 4,4′-difluorodiphenylketone(DFK) and 4,4′-methylenebis[4-(1,4-phenylene)-phthalazin-1(2H)-one] by solution polycondensation in N-methyl-2-pyrrolidone(NMP) with anhydrous K 2CO 3 as a catalyst.High molecular weight polymer was formed in 8 h at 190℃.The polymer was refined by precipitation from its 15% NMP solution with methanol as the precipitating agent.The powder of the polymer was dried in a vacuum oven under 120℃ for 48*!h and then under 200℃ for 4*!h.The intrinsic viscosity of the polymer was 0.58*!dL/g in NMP at 25℃.The polymer showed high glass transition temperature (T g) at 258℃ by DSC.The decomposition temperature for 5% weight loss (T d5) in nitrogen measured by thermogravimetric analysis occurred at 431℃.The solubility of the polymer was investigated at room temperature.The polymer was soluble in NMP,m-cresol and partially soluble in chloroform,and insoluble in N,N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO).The methylene group and bis-(phthalazinone) structure in the backbone of the polymer contribute much to the good solubility,and the rigid structure of bis(phthalazinone) retains its good thermal properties.
