In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were...In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were uniformly dispersed on the rhombus N-doped carbon(NC)nanoflakes.Transmission electron microscopic,X-ray diffraction spectrometric,and X-ray photoelectron spectroscopic analyses revealed the coexistence of metallic Co and Co oxides nanoparticles.It was found that Co/CoO_(x)@NC obtained at 500℃ annealing temperature exhibited the highest electrocatalytic OER activity,with 307 and375 m V overpotential to achieve 10 and 100 m A cm^(-2) current densities.Besides,thanks to the in-situ annealing process,Co/CoO_(x)@NC showed excellent catalytic stability with 97.4%current density retention after 24 h electrolysis at 1.66 V vs.RHE electrode potential.Further investigations revealed that the ultrasmall Co/Co Oxnanoparticles distributed on N-doped carbon template contribute significantly towards OER electrocatalysis through enlarging the activity surface areas and enhancing the intrinsic electrochemical activity due to the presence of metallic Co.展开更多
The utilization of perovskite oxide materials as catalysts for the photodegradation of organic pollutants in water is a promising and rapidly advancing field.In this study,a series of La_(1−x)Ba_(x)CoO_(3)(x=0.2,0.3,0...The utilization of perovskite oxide materials as catalysts for the photodegradation of organic pollutants in water is a promising and rapidly advancing field.In this study,a series of La_(1−x)Ba_(x)CoO_(3)(x=0.2,0.3,0.4,0.5,0.6)catalysts with varying Ba doping ratios were synthesized using the citric acid complexation-hydrothermal synthesis combined method for the degradation of phenol under visible light irradiation.Among the synthesized catalysts,La_(0.5)Ba_(0.5)CoO_(3) exhibited the highest photocatalytic activity.In addition,the photocatalytic mechanism for La_(0.5)Ba_(0.5)CoO_(3) perovskite degradation of phenol was also discussed.The synthesized catalysts were characterized using XRD,SEM,FT-IR,XPS,MPMS and other characterization techniques.The results revealed that the diffraction peak intensity of La_(1−x)Ba_(x)CoO_(3) increased with higher Ba doping ratios,and the La_(0.4)Ba_(0.6)CoO_(3) exhibited the strongest diffraction peaks.The catalyst particle sizes ranged from 10 to 50 nm,and the specific surface area decreased with increasing Ba content.Additionally,the paramagnetic properties of La_(0.5)Ba_(0.5)CoO_(3) were similar to that of La_(0.4)Ba_(0.6)CoO_(3).The experimental results suggested that the incorporation of Ba could significantly improve the catalytic performance of La_(1−x)Ba_(x)CoO_(3) perovskites,promote electron transfer and favor to the generation of hydroxyl radicals(•OH),leading to the efficiently degradation of phenol.展开更多
The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative permittivity.Low electron density is benefici...The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative permittivity.Low electron density is beneficial to reduce plasma frequency so that negative permittivity is achieved in kHz region.Negative permittivity achieved by percolating composites is restricted in practicality due to its instability nature at high temperatures.To achieve temperature-stable negative permittivity in kHz region,monophase La_(1-x)Ba_(x)CoO_(3)ceramics were prepared,and the transition from dielectric to metal was elaborated in the perspective of electrical conductivity and negative permittivity.The plasma-like negative permittivity is attained in kHz region,which is interpreted by the collective oscillation of low electron density.The temperature-stable negative permittivity is based on the fact that the plasmonic state will not be undermined at high temperatures.In addition,zero-crossing behavior of real permittivity is observed in La_(0.9)Ba_(0.1)CoO_(3)sample,which provides a promising alternative to designing epsilon-near-zero materials.This work makes the La_(1-x)Ba_(x)CoO_(3)system a source material for achieving effective negative permittivity.展开更多
Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of g...Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of great significance for the survival of living matter.Therefore,for simulating photosynthesis,it is desirable to design and fabricate a bifunctional catalyst for promoting photocatalytic water oxidation and CO_(2)reduction performances.Herein,a molecular confined synthesis strategy is reasonably proposed and applied,that is the bifunctional CoO_(x)/Co/C-T(T=700,800 and 900℃)photocatalysts prepared by the pyrolysis of molecular Co-EDTA under N_(2) and air atmosphere in turn.Among the prepared photocatalysts,the CoOx/Co/C-800 shows the best photocatalytic water oxidation activity with an oxygen yield of 51.2%.In addition,for CO_(2)reduction reaction,the CO evolution rate of 12.6μmol/h and selectivity of 75%can be achieved over this catalyst.The improved photocatalytic activities are attributed to the rapid electron transfer between the photosensitizer and the catalyst,which is strongly supported by the current densityvoltage G-V,steady-state and time-resolved photoluminescence spectra(PL).Overall,this work provides a reference for the preparation and optimization of photocatalysts with the capacity for water oxidation and CO_(2)reduction reactions.展开更多
To obtain environmentally friendly,integrated and miniaturized gas sensors for the increasing request for the Internet of Things industry and other relative areas,the ultra-thin CoO_(x)/Zn O heterogeneous film with ac...To obtain environmentally friendly,integrated and miniaturized gas sensors for the increasing request for the Internet of Things industry and other relative areas,the ultra-thin CoO_(x)/Zn O heterogeneous film with active interfacial sites was in-situ deposited on micro-electro-mechanical systems(MEMS)as H_(2)S sensor.Atomic layer deposition(ALD)was employed to in-situ fabricate the uniform Zn O thin film.ALD CoO_(x)was deposited on ZnO surface to obtain CoO_(x)/Zn O heterojunction and active interfacial sites.The ultra-thin film(20 nm)with 50 ALD Co O_(x)decorated on 250 ALD Zn O displays excellent sensing performance,including very high response(4.45@200×10^(-9))and selectivity to H_(2)S with a limit of detection(LOD)of 0.38×10^(-9),long-term sensing stability,high response/recovery performance(7.5 s/15.7 s)and mechanical strength at 230。C.Reasons for the high sensing performance of CoO_(x)/Zn O have been confirmed by series of characterizations and density functional theory(DFT)calculation.Heterojunction film thickness with Debye length,the oxygen vacancies and the synergistic effect of active interfacial sites are main reasons for the high sensing performance.The strategy by fabrication of CoO_(x)/Zn O heterogeneous film within Debye length and employing synergistic effect of active interfacial sites offers a promising route for the design of environmentally friendly gas sensors.Furthermore,the ALD technique offers a facile in-situ strategy and high-throughput fabrication of MEMS gas sensors.展开更多
基金partially supported by the National Natural Science Foundation of China(No.21805308)the Taishan Scholar Project of Shandong province,the Key Research and Development Program of Shandong Province(No.2019GSF109075)the Fundamental Research Funds for the Central Universities(No.18CX06065A,No.19CX05001A)。
文摘In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were uniformly dispersed on the rhombus N-doped carbon(NC)nanoflakes.Transmission electron microscopic,X-ray diffraction spectrometric,and X-ray photoelectron spectroscopic analyses revealed the coexistence of metallic Co and Co oxides nanoparticles.It was found that Co/CoO_(x)@NC obtained at 500℃ annealing temperature exhibited the highest electrocatalytic OER activity,with 307 and375 m V overpotential to achieve 10 and 100 m A cm^(-2) current densities.Besides,thanks to the in-situ annealing process,Co/CoO_(x)@NC showed excellent catalytic stability with 97.4%current density retention after 24 h electrolysis at 1.66 V vs.RHE electrode potential.Further investigations revealed that the ultrasmall Co/Co Oxnanoparticles distributed on N-doped carbon template contribute significantly towards OER electrocatalysis through enlarging the activity surface areas and enhancing the intrinsic electrochemical activity due to the presence of metallic Co.
基金The Fundamental Research Program for Young Scientists of Shanxi Province(Project No.202103021223294)The Fundamental Research Program of Shanxi Province(Project No.202203021211203)+1 种基金The Start-up Fund for Doctorate Scientific Research Project of Taiyuan University of Science and Technology(Project No.20232124)The Innovation and Entrepreneurship Training Program for Undergraduate,Taiyuan University of Science and Technology(Project No.DCX2024162).
文摘The utilization of perovskite oxide materials as catalysts for the photodegradation of organic pollutants in water is a promising and rapidly advancing field.In this study,a series of La_(1−x)Ba_(x)CoO_(3)(x=0.2,0.3,0.4,0.5,0.6)catalysts with varying Ba doping ratios were synthesized using the citric acid complexation-hydrothermal synthesis combined method for the degradation of phenol under visible light irradiation.Among the synthesized catalysts,La_(0.5)Ba_(0.5)CoO_(3) exhibited the highest photocatalytic activity.In addition,the photocatalytic mechanism for La_(0.5)Ba_(0.5)CoO_(3) perovskite degradation of phenol was also discussed.The synthesized catalysts were characterized using XRD,SEM,FT-IR,XPS,MPMS and other characterization techniques.The results revealed that the diffraction peak intensity of La_(1−x)Ba_(x)CoO_(3) increased with higher Ba doping ratios,and the La_(0.4)Ba_(0.6)CoO_(3) exhibited the strongest diffraction peaks.The catalyst particle sizes ranged from 10 to 50 nm,and the specific surface area decreased with increasing Ba content.Additionally,the paramagnetic properties of La_(0.5)Ba_(0.5)CoO_(3) were similar to that of La_(0.4)Ba_(0.6)CoO_(3).The experimental results suggested that the incorporation of Ba could significantly improve the catalytic performance of La_(1−x)Ba_(x)CoO_(3) perovskites,promote electron transfer and favor to the generation of hydroxyl radicals(•OH),leading to the efficiently degradation of phenol.
基金supported by the National Natural Science Foundation of China(Nos.51771104,51871146,51971119)the Natural Science Foundation of Shandong Province(No.ZR2020YQ32)the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-10-E00053)。
文摘The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative permittivity.Low electron density is beneficial to reduce plasma frequency so that negative permittivity is achieved in kHz region.Negative permittivity achieved by percolating composites is restricted in practicality due to its instability nature at high temperatures.To achieve temperature-stable negative permittivity in kHz region,monophase La_(1-x)Ba_(x)CoO_(3)ceramics were prepared,and the transition from dielectric to metal was elaborated in the perspective of electrical conductivity and negative permittivity.The plasma-like negative permittivity is attained in kHz region,which is interpreted by the collective oscillation of low electron density.The temperature-stable negative permittivity is based on the fact that the plasmonic state will not be undermined at high temperatures.In addition,zero-crossing behavior of real permittivity is observed in La_(0.9)Ba_(0.1)CoO_(3)sample,which provides a promising alternative to designing epsilon-near-zero materials.This work makes the La_(1-x)Ba_(x)CoO_(3)system a source material for achieving effective negative permittivity.
基金financially supported by the National Natural Science Foundation of China(No.22075119)the Natural Science Foundation of Gansu Province(No.21JR7RA440).
文摘Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of great significance for the survival of living matter.Therefore,for simulating photosynthesis,it is desirable to design and fabricate a bifunctional catalyst for promoting photocatalytic water oxidation and CO_(2)reduction performances.Herein,a molecular confined synthesis strategy is reasonably proposed and applied,that is the bifunctional CoO_(x)/Co/C-T(T=700,800 and 900℃)photocatalysts prepared by the pyrolysis of molecular Co-EDTA under N_(2) and air atmosphere in turn.Among the prepared photocatalysts,the CoOx/Co/C-800 shows the best photocatalytic water oxidation activity with an oxygen yield of 51.2%.In addition,for CO_(2)reduction reaction,the CO evolution rate of 12.6μmol/h and selectivity of 75%can be achieved over this catalyst.The improved photocatalytic activities are attributed to the rapid electron transfer between the photosensitizer and the catalyst,which is strongly supported by the current densityvoltage G-V,steady-state and time-resolved photoluminescence spectra(PL).Overall,this work provides a reference for the preparation and optimization of photocatalysts with the capacity for water oxidation and CO_(2)reduction reactions.
基金financially supported by the National Key Research and Development Program of China(No.2020YFB2008600)the financial support from China Scholarship Council(CSC)。
文摘To obtain environmentally friendly,integrated and miniaturized gas sensors for the increasing request for the Internet of Things industry and other relative areas,the ultra-thin CoO_(x)/Zn O heterogeneous film with active interfacial sites was in-situ deposited on micro-electro-mechanical systems(MEMS)as H_(2)S sensor.Atomic layer deposition(ALD)was employed to in-situ fabricate the uniform Zn O thin film.ALD CoO_(x)was deposited on ZnO surface to obtain CoO_(x)/Zn O heterojunction and active interfacial sites.The ultra-thin film(20 nm)with 50 ALD Co O_(x)decorated on 250 ALD Zn O displays excellent sensing performance,including very high response(4.45@200×10^(-9))and selectivity to H_(2)S with a limit of detection(LOD)of 0.38×10^(-9),long-term sensing stability,high response/recovery performance(7.5 s/15.7 s)and mechanical strength at 230。C.Reasons for the high sensing performance of CoO_(x)/Zn O have been confirmed by series of characterizations and density functional theory(DFT)calculation.Heterojunction film thickness with Debye length,the oxygen vacancies and the synergistic effect of active interfacial sites are main reasons for the high sensing performance.The strategy by fabrication of CoO_(x)/Zn O heterogeneous film within Debye length and employing synergistic effect of active interfacial sites offers a promising route for the design of environmentally friendly gas sensors.Furthermore,the ALD technique offers a facile in-situ strategy and high-throughput fabrication of MEMS gas sensors.
