Spinel metal oxides containing Mn,Co,or Fe(AB_(2)O_(4),A/B=Mn/Fe/Co)are one of the most promising nonPt electrocatalysts for oxygen reduction reaction(ORR)in alkaline conditions.However,the low conductivity of metal o...Spinel metal oxides containing Mn,Co,or Fe(AB_(2)O_(4),A/B=Mn/Fe/Co)are one of the most promising nonPt electrocatalysts for oxygen reduction reaction(ORR)in alkaline conditions.However,the low conductivity of metal oxides and the poor intrinsic activities of transition metal sites lead to unsatisfactory ORR performance.In this study,eutectic molten salt(EMS)treatment is employed to reconstruct the atomic arrangement of MnFe_(2)O_(4)electrocatalyst as a prototype for enhancing ORR performance.Comprehensive analyses by using XAFS,soft XAS,XPS,and electrochemical methods reveal that the EMS treatment reduces the oxygen vacancies and spinel inverse in MnFe_(2)O_(4)effectively,which improves the electric conductivity and increases the population of more catalytically active Mn^(2+)sites with tetrahedral coordination.Moreover,the enhanced Mn-O interaction after EMS treatment is conducive to the adsorption and activation of O_(2),which promotes the first electron transfer step(generally considered as the ratedetermining step)of the ORR process.As a result,the EMS treated MnFe_(2)O_(4)catalyst delivers a positive shift of 40 mV in the ORR half-wave potential and a two-fold enhanced mass/specific activity.This work provides a convenient approach to manipulate the atomic architecture and local electronic structure of spinel oxides as ORR electrocatalysts and a comprehensive understanding of the structureperformance relationship from the molecular/atomic scale.展开更多
Machine learning(ML)integrated with density functional theory(DFT)calculations have recently been used to accelerate the design and discovery of single-atom catalysts(SACs)by establishing deep structure–activity rela...Machine learning(ML)integrated with density functional theory(DFT)calculations have recently been used to accelerate the design and discovery of single-atom catalysts(SACs)by establishing deep structure–activity relationships.The traditional ML models are always difficult to identify the structural differences among the single-atom systems with different modification methods,leading to the limitation of the potential application range.Aiming to the structural properties of several typical two-dimensional MA_(2)Z_(4)-based single-atom systems(bare MA_(2)Z_(4) and metal single-atom doped/supported MA_(2)Z_(4)),an improved crystal graph convolutional neural network(CGCNN)classification model was employed,instead of the traditional machine learning regression model,to address the challenge of incompatibility in the studied systems.The CGCNN model was optimized using crystal graph representation in which the geometric configuration was divided into active layer,surface layer,and bulk layer(ASB-GCNN).Through ML and DFT calculations,five potential single-atom hydrogen evolution reaction(HER)catalysts were screened from chemical space of 600 MA_(2)Z_(4)-based materials,especially V_(1)/HfSn_(2)N_(4)(S)with high stability and activity(Δ_(GH*)is 0.06 eV).Further projected density of states(pDOS)analysis in combination with the wave function analysis of the SAC-H bond revealed that the SAC-dz^(2)orbital coincided with the H-s orbital around the energy level of−2.50 eV,and orbital analysis confirmed the formation ofσbonds.This study provides an efficient multistep screening design framework of metal single-atom catalyst for HER systems with similar two-dimensional supports but different geometric configurations.展开更多
Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction tem...Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 ℃ and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 ℃, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA.h/g at a rate of 0.1C （1C=148 mA/g） and a good rate capability at high rates, even up to 50C.展开更多
Carbon-doped copper ferrite(C–CuFe_(2)O_(4))was synthesized by a simple two-step hydrothermal method,which showed enhanced tetracycline hydrochloride(TCH)removal efficiency as compared to the pure CuFe_(2)O_(4) in Fe...Carbon-doped copper ferrite(C–CuFe_(2)O_(4))was synthesized by a simple two-step hydrothermal method,which showed enhanced tetracycline hydrochloride(TCH)removal efficiency as compared to the pure CuFe_(2)O_(4) in Fenton-like reaction.A removal efficiency of 94%was achieved with 0.2 g L^(-1) catalyst and 20 mmol L^(-1) H_(2)O_(2) within 90 min.We demonstrated that 5%C–CuFe_(2)O_(4) catalyst in the presence of H_(2)O_(2) was significantly efficient for TCH degradation under the near-neutral pH(5–9)without buffer.Multiple techniques,including SEM,TEM,XRD,FTIR,Raman,XPS M€ossbauer and so on,were conducted to investigate the structures,morphologies and electronic properties of as-prepared samples.The introduction of carbon can effectively accelerate electron transfer by cooperating with Cu and Fe to activate H_(2)O_(2) to generate·OH and·O_(2)^(-).Particularly,theoretical calculations display that the p,p,d orbital hybridization of C,O,Cu and Fe can form C–O–Cu and C–O–Fe bonds,and the electrons on carbon can transfer to metal Cu and Fe along the C–O–Fe and C–O–Cu channels,thus forming electron-rich reactive centers around Fe and Cu.This work provides lightful reference for the modification of spinel ferrites in Fenton-like application.展开更多
Tolylene-2,4-diisocyanate（2,4-TDI） 1 reacts with methanol through two simultaneous paths in the polyurethane reaction,which involve two different intermediates-tolylene-4-carbamatic-2-isocyanate 2 and tolylene-2-car...Tolylene-2,4-diisocyanate（2,4-TDI） 1 reacts with methanol through two simultaneous paths in the polyurethane reaction,which involve two different intermediates-tolylene-4-carbamatic-2-isocyanate 2 and tolylene-2-carbamatic-4-isocyanate 3,and the final product is tolylene-2,4-dicarbamate 4.The-CH_3 chemical shifts in benzene ring in compounds 1,2,3 and 4 can be easily tested and well distinguished,through which those four compounds are quantified and their kinetics are investigated.It shows that four rate constants for the tolylene-2,4-diisocyanate-methanol reaction in CCl_4 at 50℃are k_1=9.6×10^（-2）h^（-2）mol^（-2）min^（-1）, k_2=1.4×10^（-2）h^（-2）mol^（-2）min^（-1）,k_3=4.0×10^（-3）h^（-2）mol^（-2）min^（-1）,k_4=1.4×10^（-3）h^（-2）mol^（-2）min^（-1）.（k_1 is the reaction rate constant from compounds 1 to 2;k_2 is the reaction rate constant from compounds 1 to 3;k_3 is the reaction rate constant from compounds 3 to 4;k_4 is the reaction rate constant from compounds 2 to 4）.展开更多
The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaO...The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaOH to Zn2SiO4 of 16:1,reaction temperature of 550°C,and reaction time of 2.5 h.In order to ascertain the phases transformation and reaction processes of zinc oxide and silica,the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures.The final phases of the specimen roasted at 600°C were Na2ZnO2,Na4SiO4,Na2ZnSiO4 and NaOH.The reaction kinetic equation of roasting was determined by the shrinking unreacted core model.Aiming to investigate the reaction mechanism,two control models of reaction rate were applied:chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the diffusion through the product layer model described the reaction process well.The apparent activation energy of the roasting was 19.77 kJ/mol.展开更多
The electrochemical hydrogen evolution reaction（HER） on a non-precious electrocatalyst in an alkaline environment is of essential importance for future renewable energy. The design of advanced electrocatalysts for H...The electrochemical hydrogen evolution reaction（HER） on a non-precious electrocatalyst in an alkaline environment is of essential importance for future renewable energy. The design of advanced electrocatalysts for HER is the most important part to reduce the cost and to enhance the efficiency of water splitting. MoSis considered as one of the most promising electrocatalysts to replace the precious Pt catalyst.Herein, for the first time, we have successfully loaded MoSelectrocatalysts onto the CoOnanosheet array to catalyze HER with a low onset potential of6 mV. The high hydrogen evolution activity of MoSsupported on the CoOnanosheet array may be attributed to the increased active sites and the electronic interactions between MoSand CoO.展开更多
Two types of spinel cathode powders, LiMn2O4 and LiAl0.1Mn1.9O3.9F0.1, were synthesized by solid-state reaction, X-ray diffraction （XRD） patterns of the prepared samples were identified as the spinel structure with ...Two types of spinel cathode powders, LiMn2O4 and LiAl0.1Mn1.9O3.9F0.1, were synthesized by solid-state reaction, X-ray diffraction （XRD） patterns of the prepared samples were identified as the spinel structure with a space group of Fd 3^- m. The cubic lattice parameter was determined from least-squares fitting of the XRD data. The LiAl0.1Mn1.9O3.9F0.1 sample showed a little lower initial capacity, but better cycling performance than the LiMn2O4 sample at both room temperature and an elevated temperature. The Vanderbilt method was used to test the electrochemical conductivity of the LiMn2O4 samples. The electrochemical impedance spectroscopy （EIS） method was employed to investigate the electrochemical properties of these spinel LiMn2O4 samples.展开更多
The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 t...The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.展开更多
The wetting behavior of molten Cu on the B_(4)C-xTiB_(2)ceramic composites was investigated in this work.The results show that the contact angle of molten Cu alloy on B_(4)C-TiB_(2)ceramic composites is linear with th...The wetting behavior of molten Cu on the B_(4)C-xTiB_(2)ceramic composites was investigated in this work.The results show that the contact angle of molten Cu alloy on B_(4)C-TiB_(2)ceramic composites is linear with the composition rate of TiB_(2)or B_(4)C while the temperature is in the range of 1300 to 1350℃,consistent with the expectation of the commonly used theoretical method.However,a nonlinear relationship between the contact angle and the composition rate unexpectedly occurred at temperatures ranging from 1400 to 1500℃.The big difference of the contact angles between the molten metal and the components in the composites was found to be the key point.This result identifies that the commonly used theoretical method only works at a limited difference of the contact angle of the liquid on the different phases in the composites,and fails at a big difference.展开更多
Designing low-cost, highly efficient, and stable bifunctional electrocatalysts for both hydrogen evolution reaction（HER） and oxygen evolution reaction（OER） is of vital significance for water splitting.Herein, thre...Designing low-cost, highly efficient, and stable bifunctional electrocatalysts for both hydrogen evolution reaction（HER） and oxygen evolution reaction（OER） is of vital significance for water splitting.Herein, three-dimensional lily-like CoNi_2S_4 supported on nickel foam（CoNi_2S_4/Ni） has been fabricated by sulfuration of the Co–Ni precursor. As expected, CoNi_2S_4/Ni possesses such outstanding electrocatalytic properties that it requires an overpotential of only 54 mV at 10 mA cm^（-2） and 328 mV at 100 mA cm^（-2） for HER and OER, respectively. Furthermore, by utilizing the CoNi_2S_4/Ni electrodes as bifunctional electrocatalysts for overall water splitting, a current density of 10 mA cm^（-2） can be obtained at a voltage of only 1.56 V.展开更多
基金supported by the National Natural Science Foundation of China (12241502,52002367)the Fundamental Research Funds for the Central Universities (20720220010)the National Key Research and Development Program of China (2019YFA0405602)。
文摘Spinel metal oxides containing Mn,Co,or Fe(AB_(2)O_(4),A/B=Mn/Fe/Co)are one of the most promising nonPt electrocatalysts for oxygen reduction reaction(ORR)in alkaline conditions.However,the low conductivity of metal oxides and the poor intrinsic activities of transition metal sites lead to unsatisfactory ORR performance.In this study,eutectic molten salt(EMS)treatment is employed to reconstruct the atomic arrangement of MnFe_(2)O_(4)electrocatalyst as a prototype for enhancing ORR performance.Comprehensive analyses by using XAFS,soft XAS,XPS,and electrochemical methods reveal that the EMS treatment reduces the oxygen vacancies and spinel inverse in MnFe_(2)O_(4)effectively,which improves the electric conductivity and increases the population of more catalytically active Mn^(2+)sites with tetrahedral coordination.Moreover,the enhanced Mn-O interaction after EMS treatment is conducive to the adsorption and activation of O_(2),which promotes the first electron transfer step(generally considered as the ratedetermining step)of the ORR process.As a result,the EMS treated MnFe_(2)O_(4)catalyst delivers a positive shift of 40 mV in the ORR half-wave potential and a two-fold enhanced mass/specific activity.This work provides a convenient approach to manipulate the atomic architecture and local electronic structure of spinel oxides as ORR electrocatalysts and a comprehensive understanding of the structureperformance relationship from the molecular/atomic scale.
基金supported by the National Key R&D Program of China(2021YFA1500900)National Natural Science Foundation of China(U21A20298,22141001).
文摘Machine learning(ML)integrated with density functional theory(DFT)calculations have recently been used to accelerate the design and discovery of single-atom catalysts(SACs)by establishing deep structure–activity relationships.The traditional ML models are always difficult to identify the structural differences among the single-atom systems with different modification methods,leading to the limitation of the potential application range.Aiming to the structural properties of several typical two-dimensional MA_(2)Z_(4)-based single-atom systems(bare MA_(2)Z_(4) and metal single-atom doped/supported MA_(2)Z_(4)),an improved crystal graph convolutional neural network(CGCNN)classification model was employed,instead of the traditional machine learning regression model,to address the challenge of incompatibility in the studied systems.The CGCNN model was optimized using crystal graph representation in which the geometric configuration was divided into active layer,surface layer,and bulk layer(ASB-GCNN).Through ML and DFT calculations,five potential single-atom hydrogen evolution reaction(HER)catalysts were screened from chemical space of 600 MA_(2)Z_(4)-based materials,especially V_(1)/HfSn_(2)N_(4)(S)with high stability and activity(Δ_(GH*)is 0.06 eV).Further projected density of states(pDOS)analysis in combination with the wave function analysis of the SAC-H bond revealed that the SAC-dz^(2)orbital coincided with the H-s orbital around the energy level of−2.50 eV,and orbital analysis confirmed the formation ofσbonds.This study provides an efficient multistep screening design framework of metal single-atom catalyst for HER systems with similar two-dimensional supports but different geometric configurations.
基金Project supported by the Research Funds of the Key Laboratory of Fuel Cell Technology of Guangdong Province,ChinaProject(7411793079907)supported by the Guangzhou Special Foundation for Applied Basic Research+1 种基金Project(2013A15GX048)supported by the Dalian Science and Technology Project Foundation,ChinaProject(21376035)supported by the National Natural Science Foundation of China
文摘Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 ℃ and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 ℃, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA.h/g at a rate of 0.1C （1C=148 mA/g） and a good rate capability at high rates, even up to 50C.
基金supported by the Program for the National Natural Science Foundation of China(52070077,51879101,51779090)the National Program for Support of Top-Notch Young Professionals of China(2014)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University(IRT-13R17)Natural Science Foundation of Hunan Province(2022JJ20013,2021JJ40098).
文摘Carbon-doped copper ferrite(C–CuFe_(2)O_(4))was synthesized by a simple two-step hydrothermal method,which showed enhanced tetracycline hydrochloride(TCH)removal efficiency as compared to the pure CuFe_(2)O_(4) in Fenton-like reaction.A removal efficiency of 94%was achieved with 0.2 g L^(-1) catalyst and 20 mmol L^(-1) H_(2)O_(2) within 90 min.We demonstrated that 5%C–CuFe_(2)O_(4) catalyst in the presence of H_(2)O_(2) was significantly efficient for TCH degradation under the near-neutral pH(5–9)without buffer.Multiple techniques,including SEM,TEM,XRD,FTIR,Raman,XPS M€ossbauer and so on,were conducted to investigate the structures,morphologies and electronic properties of as-prepared samples.The introduction of carbon can effectively accelerate electron transfer by cooperating with Cu and Fe to activate H_(2)O_(2) to generate·OH and·O_(2)^(-).Particularly,theoretical calculations display that the p,p,d orbital hybridization of C,O,Cu and Fe can form C–O–Cu and C–O–Fe bonds,and the electrons on carbon can transfer to metal Cu and Fe along the C–O–Fe and C–O–Cu channels,thus forming electron-rich reactive centers around Fe and Cu.This work provides lightful reference for the modification of spinel ferrites in Fenton-like application.
基金the financial support from the National Natural Science Foundation of China(No. 20676074)the National Natural Science Foundation of Shandong Province(No.Y2004B04).
文摘Tolylene-2,4-diisocyanate（2,4-TDI） 1 reacts with methanol through two simultaneous paths in the polyurethane reaction,which involve two different intermediates-tolylene-4-carbamatic-2-isocyanate 2 and tolylene-2-carbamatic-4-isocyanate 3,and the final product is tolylene-2,4-dicarbamate 4.The-CH_3 chemical shifts in benzene ring in compounds 1,2,3 and 4 can be easily tested and well distinguished,through which those four compounds are quantified and their kinetics are investigated.It shows that four rate constants for the tolylene-2,4-diisocyanate-methanol reaction in CCl_4 at 50℃are k_1=9.6×10^（-2）h^（-2）mol^（-2）min^（-1）, k_2=1.4×10^（-2）h^（-2）mol^（-2）min^（-1）,k_3=4.0×10^（-3）h^（-2）mol^（-2）min^（-1）,k_4=1.4×10^（-3）h^（-2）mol^（-2）min^（-1）.（k_1 is the reaction rate constant from compounds 1 to 2;k_2 is the reaction rate constant from compounds 1 to 3;k_3 is the reaction rate constant from compounds 3 to 4;k_4 is the reaction rate constant from compounds 2 to 4）.
基金Projects(51774070,51204054)supported by the National Natural Science Foundation of ChinaProject(150204009)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(2014CB643405)supported by the National Basic Research Program of China
文摘The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaOH to Zn2SiO4 of 16:1,reaction temperature of 550°C,and reaction time of 2.5 h.In order to ascertain the phases transformation and reaction processes of zinc oxide and silica,the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures.The final phases of the specimen roasted at 600°C were Na2ZnO2,Na4SiO4,Na2ZnSiO4 and NaOH.The reaction kinetic equation of roasting was determined by the shrinking unreacted core model.Aiming to investigate the reaction mechanism,two control models of reaction rate were applied:chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the diffusion through the product layer model described the reaction process well.The apparent activation energy of the roasting was 19.77 kJ/mol.
基金support from the National Natural Science Foundation of China (51402100 and 21573066)the Provincial Natural Science Foundation of Hunan (2016JJ1006 and 2016TP1009)
文摘The electrochemical hydrogen evolution reaction（HER） on a non-precious electrocatalyst in an alkaline environment is of essential importance for future renewable energy. The design of advanced electrocatalysts for HER is the most important part to reduce the cost and to enhance the efficiency of water splitting. MoSis considered as one of the most promising electrocatalysts to replace the precious Pt catalyst.Herein, for the first time, we have successfully loaded MoSelectrocatalysts onto the CoOnanosheet array to catalyze HER with a low onset potential of6 mV. The high hydrogen evolution activity of MoSsupported on the CoOnanosheet array may be attributed to the increased active sites and the electronic interactions between MoSand CoO.
基金This work was financially supported by the National Natural Science Foundation of China (No.50272012).
文摘Two types of spinel cathode powders, LiMn2O4 and LiAl0.1Mn1.9O3.9F0.1, were synthesized by solid-state reaction, X-ray diffraction （XRD） patterns of the prepared samples were identified as the spinel structure with a space group of Fd 3^- m. The cubic lattice parameter was determined from least-squares fitting of the XRD data. The LiAl0.1Mn1.9O3.9F0.1 sample showed a little lower initial capacity, but better cycling performance than the LiMn2O4 sample at both room temperature and an elevated temperature. The Vanderbilt method was used to test the electrochemical conductivity of the LiMn2O4 samples. The electrochemical impedance spectroscopy （EIS） method was employed to investigate the electrochemical properties of these spinel LiMn2O4 samples.
基金Ting-ting FENG acknowledges the financial support from Professor Paul V.BRAUN at Department of Materials Science and Engineering,University of Illinois at Urbana-Champaign,the support from Chinese Scholarship Council during her visit to University of Illinois at Urbana-Champaign,partial financial supports from Department of Science and Technology of Sichuan Province,China(2019YFH0002,2019YFG0222 and 2019YFG0526).The research was partly carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities,University of Illinois at Urbana-Champaign.
文摘The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.
基金Funded by National Natural Science Foundation of China(Nos.51521001,51832003,and 51911530153)。
文摘The wetting behavior of molten Cu on the B_(4)C-xTiB_(2)ceramic composites was investigated in this work.The results show that the contact angle of molten Cu alloy on B_(4)C-TiB_(2)ceramic composites is linear with the composition rate of TiB_(2)or B_(4)C while the temperature is in the range of 1300 to 1350℃,consistent with the expectation of the commonly used theoretical method.However,a nonlinear relationship between the contact angle and the composition rate unexpectedly occurred at temperatures ranging from 1400 to 1500℃.The big difference of the contact angles between the molten metal and the components in the composites was found to be the key point.This result identifies that the commonly used theoretical method only works at a limited difference of the contact angle of the liquid on the different phases in the composites,and fails at a big difference.
基金supported by the National Natural Science Foundation of China(21376105,21576113)~~
文摘Designing low-cost, highly efficient, and stable bifunctional electrocatalysts for both hydrogen evolution reaction（HER） and oxygen evolution reaction（OER） is of vital significance for water splitting.Herein, three-dimensional lily-like CoNi_2S_4 supported on nickel foam（CoNi_2S_4/Ni） has been fabricated by sulfuration of the Co–Ni precursor. As expected, CoNi_2S_4/Ni possesses such outstanding electrocatalytic properties that it requires an overpotential of only 54 mV at 10 mA cm^（-2） and 328 mV at 100 mA cm^（-2） for HER and OER, respectively. Furthermore, by utilizing the CoNi_2S_4/Ni electrodes as bifunctional electrocatalysts for overall water splitting, a current density of 10 mA cm^（-2） can be obtained at a voltage of only 1.56 V.
