In this work,we report the growth of uniformly dispersed bimetallic cobalt-palladium nanoparticles(NPs) on reduced graphene oxide(RGO) nanosheets to prepare CoPd-RGO composites via a two-step procedure,where firstly f...In this work,we report the growth of uniformly dispersed bimetallic cobalt-palladium nanoparticles(NPs) on reduced graphene oxide(RGO) nanosheets to prepare CoPd-RGO composites via a two-step procedure,where firstly formed Co NPs are used as seeds for the subsequent growth of Pd.The generation of Co NPs on RGO is performed by an in-situ reduction reaction with the reducer ethylene glycol under oil bath at180 ℃.According to composition,size and microstructure analyses,NPs in the resulting CoPd-RGO have an average particle size of 5 nm,and Pd is added to one side of Co NPs,thus forming Co-Pd bimetallic interfaces.The involved formation mechanism is suggested.The composite is used as an electro-catalyst for the formic acid oxidation in alkaline electrolyte,and the catalytic performance is investigated by cyclic voltammetry and chronopotentiometry etc.The results show that the composite has the highest electrocatalytic activity,the best electrochemical stability and the highest resistance to CO poisoning than those of the monometallic composite and commercial Pd black at the same loading.This is due not only to the small size of NPs with Co-Pd bimetallic interfaces providing more active atoms accessible for reactants,but also to the electric synergistic effect between metals and graphene.展开更多
Thecorrelation between composition, structure, chemical bond, and thermoelectric proper tiesof Si doped boroncarbidesisstudied using SCF DV Xαmethod. Thecalculationsshow that Siatom firstlysubstitutes Bor Catomson th...Thecorrelation between composition, structure, chemical bond, and thermoelectric proper tiesof Si doped boroncarbidesisstudied using SCF DV Xαmethod. Thecalculationsshow that Siatom firstlysubstitutes Bor Catomson theend of boron carbidechain, then may occupyinterstitialsites when Siis dopedin boron carbide, anditisdifficultfor SitosubstituteBor Catom in thecenter of chain orintheicosahedron. Arepresentativestructural unitcontain ing an Si atom is 〔C B Si〕ε+ 〔B11 C〕ε , whilethe structural unit without Siis 〔C B B ( C)〕δ 〔B11 C〕δ+ . Afteradding Sitotheboroncarbides,theenergyrequired bythe dispro portionation reaction decreases,theconcentrationofthecarriersincreases,andthereare more pathsfor the bipolaron to hopping. At thesametime, the covalent bond becomes weaker, andthethermal conductivity decreases. Therefore, thethermoelectric property of Si dopedboron carbidesisimproved .展开更多
The thermodynamic properties of Cu-Ce-S and Cu-Y-S liquid solutions were studied by the chemical equilibrium technique at 1200℃. The equilibrium constants and the standard free energies of formation of CeS and YS wer...The thermodynamic properties of Cu-Ce-S and Cu-Y-S liquid solutions were studied by the chemical equilibrium technique at 1200℃. The equilibrium constants and the standard free energies of formation of CeS and YS were determined for the reactions: CeS=[Ce]+[S] and YS = [Y]+[S] . For the solution of Ce_(1) and Y_(l) in pure Cu according to the reactions: Ce_(1)= [Ce] and Y_(1)= [Y] , the standard free energies of solutions were obtained. The first order and second order interaction coefficients between solute elements as well as the activity coefficients γ_(Ce)~0 and γ_Y^0 in liquid Cu were also determined.展开更多
Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.The compound crystallizes in an orthorhombic unit cell,space group D_(2h)^(17)-Cmcm with a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃. ...Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.The compound crystallizes in an orthorhombic unit cell,space group D_(2h)^(17)-Cmcm with a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃. Sr_(0.5)Ca_(0.5)CuO_2 is s black p-type semiconductor with resistivity 53Ω.cm at room tempersture.展开更多
Graphene,a promising two-dimensional carbon material,has been extensively employed in dye-sensitized solar cells(DSSCs)with encouraging results.However,how graphene improves the power conversion efficiency is still un...Graphene,a promising two-dimensional carbon material,has been extensively employed in dye-sensitized solar cells(DSSCs)with encouraging results.However,how graphene improves the power conversion efficiency is still unclear.In this research,a series of dyes with pristine,doped and hole graphene based on the dye WS5 were designed and systematically investigated by density functional theory(DFT)and time-dependent DFT(TD-DFT),aimed at revealing the effect of these functionalized graphenes on photophysical properties.The results based on the absorption properties reveal that introducing functionalized graphene not only enhances absorption intensity,but also expands the absorption spectrum,which will lead to a better photocurrent response.According to an analysis of the intermolecular interaction between dye and I_(2),all the designed dyes possess a slow electron recombination rate,except WS5-HoS,and then possibly an increasing VOC.Additionally,J_(ph)increases steadily as the electronegativity of the doped atoms(C,Si and Ge)in graphene increases.The dyes with the insertion of short functionalized graphene exhibit a superior performance in J_(ph)to that of long functionalized graphene.Meanwhile,using graphene to decorate the dye WS5 could adjust energy levels to narrow the energy gap.Dyes with short functionalized graphene exhibit the smallest HOMO-LUMO gaps,followed by long functionalized graphene and the dye WS5.With the enhancement in the electronegativity of doped atoms(C,Si and Ge)in graphene,the energy gap decreases steadily.Inserting functionalized graphene facilitates electron transfer properties due to lower aromaticities,especially for dyes with short functionalized graphene.Taken all together,the introduction of short functionalized graphene in a dye is a valid approach to increase overall efficiency,especially for graphene doped with atoms of larger electronegativity,so the photophysical properties of DSSCs could be boosted in the future.展开更多
In this work,the electrical property of Au/graphene oxide/p-InP hetero-structure has been evaluated by 1-V and C-V measure-ments in dark and iluminated conditions(visible light).The diode exhibited significant rectify...In this work,the electrical property of Au/graphene oxide/p-InP hetero-structure has been evaluated by 1-V and C-V measure-ments in dark and iluminated conditions(visible light).The diode exhibited significant rectifying behavior,thus indicating the heterojunction-lype diode.The key electrical parameters of heterojunction diode including ideality factor(n),series resistance(R),shunt resistance(Rsh),and barrier height(Фb)are estimated from I-V data based on the theory of thermionic emission.The modifed Norde and Cheung's methods were utilized to evaluate the electrical parameters and compared the results.The current conduction mechanism at different voltage regions of I-V has also been investigated.The variation of 1/C versus voltage signifies linearity at high frequency(1 MHz),indicating that the type of heterojunction can be abrupt.The experimental outcomes of this study revealed that the performance of heterojunction diode in dark is considerably good as compared to the ilumination condition with respect to the lower values of Фp,n,R,and interface state density(Nss).展开更多
基金supported by the PAPD (No. 50831004)the Fundamental Research Funds for the Central Universities,the Innovation Fund of Jiangsu Province (No. BY2013072-06)+2 种基金the Natural Science Foundation of Jiangsu Province (No. 2012729)the National Natural Science Foundation of China (Nos. 51171078 and 11374136)the State Key Program for Basic Research of China (No. 2010CB631004)
文摘In this work,we report the growth of uniformly dispersed bimetallic cobalt-palladium nanoparticles(NPs) on reduced graphene oxide(RGO) nanosheets to prepare CoPd-RGO composites via a two-step procedure,where firstly formed Co NPs are used as seeds for the subsequent growth of Pd.The generation of Co NPs on RGO is performed by an in-situ reduction reaction with the reducer ethylene glycol under oil bath at180 ℃.According to composition,size and microstructure analyses,NPs in the resulting CoPd-RGO have an average particle size of 5 nm,and Pd is added to one side of Co NPs,thus forming Co-Pd bimetallic interfaces.The involved formation mechanism is suggested.The composite is used as an electro-catalyst for the formic acid oxidation in alkaline electrolyte,and the catalytic performance is investigated by cyclic voltammetry and chronopotentiometry etc.The results show that the composite has the highest electrocatalytic activity,the best electrochemical stability and the highest resistance to CO poisoning than those of the monometallic composite and commercial Pd black at the same loading.This is due not only to the small size of NPs with Co-Pd bimetallic interfaces providing more active atoms accessible for reactants,but also to the electric synergistic effect between metals and graphene.
文摘Thecorrelation between composition, structure, chemical bond, and thermoelectric proper tiesof Si doped boroncarbidesisstudied using SCF DV Xαmethod. Thecalculationsshow that Siatom firstlysubstitutes Bor Catomson theend of boron carbidechain, then may occupyinterstitialsites when Siis dopedin boron carbide, anditisdifficultfor SitosubstituteBor Catom in thecenter of chain orintheicosahedron. Arepresentativestructural unitcontain ing an Si atom is 〔C B Si〕ε+ 〔B11 C〕ε , whilethe structural unit without Siis 〔C B B ( C)〕δ 〔B11 C〕δ+ . Afteradding Sitotheboroncarbides,theenergyrequired bythe dispro portionation reaction decreases,theconcentrationofthecarriersincreases,andthereare more pathsfor the bipolaron to hopping. At thesametime, the covalent bond becomes weaker, andthethermal conductivity decreases. Therefore, thethermoelectric property of Si dopedboron carbidesisimproved .
文摘The thermodynamic properties of Cu-Ce-S and Cu-Y-S liquid solutions were studied by the chemical equilibrium technique at 1200℃. The equilibrium constants and the standard free energies of formation of CeS and YS were determined for the reactions: CeS=[Ce]+[S] and YS = [Y]+[S] . For the solution of Ce_(1) and Y_(l) in pure Cu according to the reactions: Ce_(1)= [Ce] and Y_(1)= [Y] , the standard free energies of solutions were obtained. The first order and second order interaction coefficients between solute elements as well as the activity coefficients γ_(Ce)~0 and γ_Y^0 in liquid Cu were also determined.
文摘Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.The compound crystallizes in an orthorhombic unit cell,space group D_(2h)^(17)-Cmcm with a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃. Sr_(0.5)Ca_(0.5)CuO_2 is s black p-type semiconductor with resistivity 53Ω.cm at room tempersture.
基金support of this research from the National Natural Science Foundation of China(51779065 and 51579057)the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(2019DX11).
文摘Graphene,a promising two-dimensional carbon material,has been extensively employed in dye-sensitized solar cells(DSSCs)with encouraging results.However,how graphene improves the power conversion efficiency is still unclear.In this research,a series of dyes with pristine,doped and hole graphene based on the dye WS5 were designed and systematically investigated by density functional theory(DFT)and time-dependent DFT(TD-DFT),aimed at revealing the effect of these functionalized graphenes on photophysical properties.The results based on the absorption properties reveal that introducing functionalized graphene not only enhances absorption intensity,but also expands the absorption spectrum,which will lead to a better photocurrent response.According to an analysis of the intermolecular interaction between dye and I_(2),all the designed dyes possess a slow electron recombination rate,except WS5-HoS,and then possibly an increasing VOC.Additionally,J_(ph)increases steadily as the electronegativity of the doped atoms(C,Si and Ge)in graphene increases.The dyes with the insertion of short functionalized graphene exhibit a superior performance in J_(ph)to that of long functionalized graphene.Meanwhile,using graphene to decorate the dye WS5 could adjust energy levels to narrow the energy gap.Dyes with short functionalized graphene exhibit the smallest HOMO-LUMO gaps,followed by long functionalized graphene and the dye WS5.With the enhancement in the electronegativity of doped atoms(C,Si and Ge)in graphene,the energy gap decreases steadily.Inserting functionalized graphene facilitates electron transfer properties due to lower aromaticities,especially for dyes with short functionalized graphene.Taken all together,the introduction of short functionalized graphene in a dye is a valid approach to increase overall efficiency,especially for graphene doped with atoms of larger electronegativity,so the photophysical properties of DSSCs could be boosted in the future.
基金The authors would like to thank the National Science Fund for Excellent Young Scholars(51722509)National Key Research and Development Program of China(2017YFB1104700)+1 种基金Program for Science and Technology Innovation Group of Shaanxi Province(2019TD-011)Key Research and Development Program of Shaanxi Province(2020ZDLGY04-02)for support.
文摘In this work,the electrical property of Au/graphene oxide/p-InP hetero-structure has been evaluated by 1-V and C-V measure-ments in dark and iluminated conditions(visible light).The diode exhibited significant rectifying behavior,thus indicating the heterojunction-lype diode.The key electrical parameters of heterojunction diode including ideality factor(n),series resistance(R),shunt resistance(Rsh),and barrier height(Фb)are estimated from I-V data based on the theory of thermionic emission.The modifed Norde and Cheung's methods were utilized to evaluate the electrical parameters and compared the results.The current conduction mechanism at different voltage regions of I-V has also been investigated.The variation of 1/C versus voltage signifies linearity at high frequency(1 MHz),indicating that the type of heterojunction can be abrupt.The experimental outcomes of this study revealed that the performance of heterojunction diode in dark is considerably good as compared to the ilumination condition with respect to the lower values of Фp,n,R,and interface state density(Nss).
