The mixture of(2NaBH4+ MnCl2) was ball milled in a magneto-mill. No gas release was detected. The XRD patterns of the ball milled mixture exhibit only the Bragg diffraction peaks of the Na Cl-type salt which on the ba...The mixture of(2NaBH4+ MnCl2) was ball milled in a magneto-mill. No gas release was detected. The XRD patterns of the ball milled mixture exhibit only the Bragg diffraction peaks of the Na Cl-type salt which on the basis of the present X-ray diffraction results and the literature is likely to be a solid solution Na(Cl)x(BH4)(1-x), possessing a cubic Na Cl-type crystalline structure. No presence of any crystalline hydride was detected by powder X-ray diffraction which clearly shows that NaBH4in the initial mixture must have reacted with MnCl2forming a Na Cl-type by-product and another hydride that does not exhibit X-ray Bragg diffraction peaks. Mass spectrometry(MS) of gas released from the ball milled mixture during combined MS/thermogravimetric analysis(TGA)/differential scanning calorimetry(DSC) experiments, confirms mainly hydrogen(H2) with a small quantity of diborane gas, B2H6. The Fourier transform infra-red(FT-IR) spectrum of the ball milled(2NaBH4+ MnCl2) is quite similar to the FT-IR spectrum of crystalline manganese borohydride, c-Mn(BH4)2, synthesized by ball milling, which strongly suggests that the amorphous hydride mechano-chemically synthesized during ball milling could be an amorphous manganese borohydride. Remarkably, the process of solvent filtration and extraction at 42 °C, resulted in the transformation of mechano-chemically synthesized amorphous manganese borohydride to a nanostructured,crystalline, c-Mn(BH4)2hydride.展开更多
A novel and simple synthetic way using NaBH4 in the mixure of H2O-THF was applied to prepare 1,2-bis(diphenylphosphinoborane)ethane, dppe(BH3)2, in high yield and purity. The phosphanylborohydride compound dppe(BH3)2 ...A novel and simple synthetic way using NaBH4 in the mixure of H2O-THF was applied to prepare 1,2-bis(diphenylphosphinoborane)ethane, dppe(BH3)2, in high yield and purity. The phosphanylborohydride compound dppe(BH3)2 was isolated in the form of colorless crystals and characterized by single crystal X-ray diffraction, 1H, 13C, 31P and 11B NMR spectroscopy. Prismatic colorless crystals of dppe(BH3)2 were obtained in monoclinic crystal system and space group P21 with two asymmetric units in the unit cell. Lattice parameters were: a = 11.657(2), b = 17.237(2), c = 12.764(2) ?, β = 98.735(14)°, 2535.0(7) ?展开更多
High dispersive copper nanoparticles were prepared by chemical reduction method using potassium borohydride as reducing agent.The effects of reactant ratio,concentration of CuSO4,reaction temperature,and dispersant on...High dispersive copper nanoparticles were prepared by chemical reduction method using potassium borohydride as reducing agent.The effects of reactant ratio,concentration of CuSO4,reaction temperature,and dispersant on the size of product and conversion rate were studied.The morphologies of copper nanoparticles were characterized by scanning electron microscopy.The results show that the optimum process conditions are as follows:the molar ratio of KBH4 to CuSO4 is 0.75(3:4),concentration of CuSO4 is 0.4 mol/L,reaction temperature is 30℃,and dispersant is n-butyl alcohol.The average particles size of copper powders with spherical shape gained is about 100 nm.展开更多
Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH 4) for hydrogen generation.At solution temperature of 0 C,the methanolys...Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH 4) for hydrogen generation.At solution temperature of 0 C,the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate,which makes it suitable for applications under the circumstance of low environmental temperature.The byproduct of methanolysis reaction is analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct,NaB(OCH 3) 4.The catalytic activity of Co/Al2O3 towards NaBH 4 methanolysis can be further improved by appropriate calcination treatment.The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.展开更多
Ionic liquids(ILs) are attracting much attention in various fields of chemical synthesis, electrochemical applications, liquid-liquid extractions, as well as biotransformations. Among those fields, the application o...Ionic liquids(ILs) are attracting much attention in various fields of chemical synthesis, electrochemical applications, liquid-liquid extractions, as well as biotransformations. Among those fields, the application of ILs as the potential green solvent for a wide variety of synthetic processes is an area of intense researches. High yield, high selectivity, and good catalytic charac-teristics have usually been achieved. After the isolation of products, ILs can usually be recovered and recycled many times by simple treating procedures, such as, filtration, extraction, and dryness.展开更多
Stability of borohydrides is determined by the localization of the negative charge on the boron atom.Ionic liquids(ILs) allow to modify the stability of the borohydrides and promote new dehydrogenation pathways with a...Stability of borohydrides is determined by the localization of the negative charge on the boron atom.Ionic liquids(ILs) allow to modify the stability of the borohydrides and promote new dehydrogenation pathways with a lower activation energy. The combination of borohydride and IL is very easy to realize and no expensive rare earth metals are required. The composite of the ILs with complex hydrides decreases the enthalpy and activation energy for the hydrogen desorption. The Coulomb interaction between borohydride and IL leads to a destabilization of the materials with a significantly lower enthalpy for hydrogen desorption. Here, we report a simple ion exchange reaction using various ILs, such as vinylbenzyltrimethylammonium chloride([VBTMA][Cl]), 1-butyl-3-methylimidazolium chloride([bmim][Cl]), and 1-ethyl-1-methylpyrrolidinium bromide([EMPY][Br]) with NaBH4 to decrease the hydrogen desorption temperature. Dehydrogenation of 1-butyl-3-methylimidazolium borohydride([bmim][BH4]) starts below 100℃. The quantity of desorbed hydrogen ranges between 2.4 wt% and 2.9 wt%, which is close to the theoretical content of hydrogen. The improvement in dehydrogenation is due to the strong amine cation that destabilizes borohydride by charge transfer.展开更多
PtRuIn/C electrocatalysts( 20% metal loading by weight) were prepared by sodium borohydride reduction process using H_2PtCl6·6H_2O,RuCl_3·xH_2O and InCl_3·xH_2O as metal sources,borohydride as reducing ...PtRuIn/C electrocatalysts( 20% metal loading by weight) were prepared by sodium borohydride reduction process using H_2PtCl6·6H_2O,RuCl_3·xH_2O and InCl_3·xH_2O as metal sources,borohydride as reducing agent and Carbon Vulcan XC72 as support. The synthetized PtRuIn/C electrocatalysts were characterized by X-ray diffraction( XRD),energy dispersive analysis( EDX),transmission electron microscopy( TEM),cyclic voltammetry( CV),chronoamperommetry( CA) and polarization curves in alkaline and acidic electrolytes( single cell experiments). The XRD patterns showPtpeaks are attributed to the face-centered cubic( fcc) structure,and a shift of Pt( fcc) peaks indicates that Ru or In is incorporated into Ptlattice. TEMmicrographs showmetal nanoparticles with an average nanoparticle size between 2.7 and 3.5 nm. Methanol oxidation in acidic and alkaline electrolytes was investigated at room temperature,by CV and CA. PtRu/C( 50 ∶ 50) shows the highest activity among all electrocatalysts in study considering methanol oxidation for acidic and alkaline electrolyte. Polarization curves at 80 ℃ showPtRuIn/C( 50 ∶ 25 ∶ 25)with superior performance for methanol oxidation,when compared to Pt/C,PtIn/C and PtRu/C for both electrolytes. The best performance obtained by PtRuIn/C( 50 ∶ 25 ∶ 25) in real conditions could be associated with the increased kinetics reaction and/or with the occurrence simultaneously of the bifunctional mechanism and electronic effect resulting from the presence of Ptalloy.展开更多
The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte...The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.展开更多
Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hy...Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hydrogen and enhance the utilization of borohydride, Ti/Zr metal powders has been added into the parent LmNi4.78Mn0.22 (where Lm is La-richened mischmetal) alloy (LNM) by ball milling and heat treatment methods. It is found that the addition of Ti/Zr metal powders lowers the electrochemical catalytic activity of the electrodes, at the same time, restrains the generation of hydrogen and enhances the utilization of the fuel. All the results show that the hydrogen generation rate or the utilization of the fuel is directly relative to the electrochemical catalytic activity or the discharge capability of the electrodes. The utilization of the fuel increases with discharge current density. It is very important to find a balance between the discharge capability and the utilization of the fuel.展开更多
A simple and convenient procedure for the preparation of amines from aldehydes and ketones with sodium borohydride activated by silica chloride as a catalyst under solvent-free conditions is described.A variety of ali...A simple and convenient procedure for the preparation of amines from aldehydes and ketones with sodium borohydride activated by silica chloride as a catalyst under solvent-free conditions is described.A variety of aliphatic and aromatic aldehydes,ketones and amines when mixed with NaBH;/silica chloride at room temperature,afforded excellent yield of the corresponding amines.展开更多
We reported an inexpensive and high-efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the sol...We reported an inexpensive and high-efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt%based on all the reactants can be achieved with excellent hydrogen generation kinetics.展开更多
The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg(BH4)2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. ...The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg(BH4)2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. It is found that the ambient pressure phases of meta-stable I41/amd and unstable P-3ml proposed recently are extra stable and cannot decompose under high pressure. Enthalpy calculation indicates that the ground state of F222 structure proposed by Zhou et al. [2009 Phys. Rev. B 79 212102] will transfer to I41/amd at 0.7 GPa, and then to a P-3ml structure at 6.3 GPa. The experimental P6122 structure (a-phase) transfers to I41/amd at 1.2 GPa. Furthermore, both I41/arnd and P-3ml can exist as high volumetric hydrogen density phases at low pressure. Their theoretical volumetric hydrogen densities reach 146.351 g H2/L and 134.028 g H2/L at ambient pressure, respectively. The calculated phonon dispersion curve shows that the I41/amd phase is dynamically stable in a pressure range from 0 to 4 CPa and the P-3ral phase is stable at pressures higher than 1 GPa. So the I41/arnd phase may be synthesized under high pressure and retained to ambient pressure. Energy band structures show that they are both always ionic crystalline and insulating with a band-gap of about 5 eV in this pressure range. In addition, they each have an anisotropic compressibility. The c axis of these structures is easy to compress. Especially, the c axis and volume of P-3ml phase are extraordinarily compressible, showing that compression along the e axis can increase the volumetric hydrogen content for both I41/amd and P-3ml structures.展开更多
We reported a low cost,high efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixtu...We reported a low cost,high efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt% based on all the reactants can be achieved with excellent hydrogen generation kinetics.展开更多
Problems associated with carbon support corrosion under operating fuel cell conditions require the identification of alternative supports for platinum-based nanosized electrocatalysts.Platinum supported on manganese v...Problems associated with carbon support corrosion under operating fuel cell conditions require the identification of alternative supports for platinum-based nanosized electrocatalysts.Platinum supported on manganese vanadate(Pt/MnV_(2)O_(6))was prepared by microwave irradiation method and characterized using X-ray diffraction,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy with energy dispersive spectroscopy,and transmission electron microscopy.The borohydride oxidation reaction(BOR)on Pt/MnV_(2)O_(6) was studied in highly alkaline media using voltammetry,chronoamperometry,and electrochemical impedance spectroscopy.BOR electrocatalytic activity of Pt/MnV_(2)O_(6) was also compared with that of commercial Pt/C(46 wt%Pt)electrocatalyst.The apparent activation energy of BOR at Pt/MnV_(2)O_(6) was estimated to be 32 k J mol^(-1) and the order of reaction to be 0.51,indicating that borohydride hydrolysis proceeds in parallel with its oxidation.Long-term stability of Pt/MnV_(2)O_(6) under BOR typical conditions was observed.A laboratory-scale direct borohydride fuel cell assembled with a Pt/MnV_(2)O_(6) anode reached a specific power of 274 W g^(-1).Experimental results on Pt/MnV_(2)O_(6) were complemented by DFT calculations,which indicated good adherence of Pt to MnV_(2)O_(6),beneficial for electrocatalyst stability.展开更多
It was established that application of bipolar membrane in a direct borohydride fuel cell (DBFC) with H2O2 co-generation enabled to keep constant pH in catholyte within 2.5 - 3.2 limits, which allowed us to carry out ...It was established that application of bipolar membrane in a direct borohydride fuel cell (DBFC) with H2O2 co-generation enabled to keep constant pH in catholyte within 2.5 - 3.2 limits, which allowed us to carry out treatment of water polluted by organic compounds in fuel cell catholyte. Treatment of water was carried out by electro-Fenton and photo-electro-Fenton methods. With the view of efficiency, photo-electro-Fenton method of treatment was the most efficient, which enabled to decrease COD of catholytes containing (in each case) phenol, valsaren, 400 g/L dymethoate (BI-58) and valsaciper from 500 ppm to 30, 11, 9 and 3 ppm, respectively after 180 min treatment. By increasing the catholyte temperature from 20℃?to 40℃?in the same period, phenol COD fell to 5 ppm.展开更多
A new chitosan-supported borohydride reducing reagent (CBER) was prepared by treatment of KBH4 with the resin of chitosan derivative, which was first synthesized from: the reaction of cross-linked chitosan microsphere...A new chitosan-supported borohydride reducing reagent (CBER) was prepared by treatment of KBH4 with the resin of chitosan derivative, which was first synthesized from: the reaction of cross-linked chitosan microsphere with glycidyl trimethylammonium chloride. CBER could reduce aromatic carbonyl compound to corresponding alcohol.展开更多
Aromatic nitro compounds are reduced to correspouding amiues in ethanol by borohydride exchauge resin(BER)in the presence of transition metal Pd,Co,Ni,Cu)compounds as catalysts.
A highly efficient and facile protocol for the selective reduction of carboxylic acid of Fenofibric acid to corresponding alcohol was developed. The selective reduction was carried out by activation of carboxylic acid...A highly efficient and facile protocol for the selective reduction of carboxylic acid of Fenofibric acid to corresponding alcohol was developed. The selective reduction was carried out by activation of carboxylic acid by mixed anhydride followed by the reaction of sodium borohydride in presence of methanol. This is the first example of chemoselective reduction of carboxylic acid to alcohol in presence of a ketone without any external catalyst or ligand in a single step. The reaction offers wide applicability for the selective carboxylic group reduction methodology. The chemoselective reduction was demonstrated by the reduction of Fenofibric acid, an active metabolite of the drug Fenofibrate, to corresponding alcohol in excellent selectivity, yield, and purity.展开更多
基金supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery grant to Prof. R.A. Varin
文摘The mixture of(2NaBH4+ MnCl2) was ball milled in a magneto-mill. No gas release was detected. The XRD patterns of the ball milled mixture exhibit only the Bragg diffraction peaks of the Na Cl-type salt which on the basis of the present X-ray diffraction results and the literature is likely to be a solid solution Na(Cl)x(BH4)(1-x), possessing a cubic Na Cl-type crystalline structure. No presence of any crystalline hydride was detected by powder X-ray diffraction which clearly shows that NaBH4in the initial mixture must have reacted with MnCl2forming a Na Cl-type by-product and another hydride that does not exhibit X-ray Bragg diffraction peaks. Mass spectrometry(MS) of gas released from the ball milled mixture during combined MS/thermogravimetric analysis(TGA)/differential scanning calorimetry(DSC) experiments, confirms mainly hydrogen(H2) with a small quantity of diborane gas, B2H6. The Fourier transform infra-red(FT-IR) spectrum of the ball milled(2NaBH4+ MnCl2) is quite similar to the FT-IR spectrum of crystalline manganese borohydride, c-Mn(BH4)2, synthesized by ball milling, which strongly suggests that the amorphous hydride mechano-chemically synthesized during ball milling could be an amorphous manganese borohydride. Remarkably, the process of solvent filtration and extraction at 42 °C, resulted in the transformation of mechano-chemically synthesized amorphous manganese borohydride to a nanostructured,crystalline, c-Mn(BH4)2hydride.
基金Partial support of this work by the Turkish Academy of Sciences and the Scientific and Technological Research Council of Turkey(TUBITAK,Project No:105M357)is gratefully acknowledgedL.T.Y ildirim thanks Hacettepe University Scientific Research Unit(grant,No.04 A602004)for financial support.
文摘A novel and simple synthetic way using NaBH4 in the mixure of H2O-THF was applied to prepare 1,2-bis(diphenylphosphinoborane)ethane, dppe(BH3)2, in high yield and purity. The phosphanylborohydride compound dppe(BH3)2 was isolated in the form of colorless crystals and characterized by single crystal X-ray diffraction, 1H, 13C, 31P and 11B NMR spectroscopy. Prismatic colorless crystals of dppe(BH3)2 were obtained in monoclinic crystal system and space group P21 with two asymmetric units in the unit cell. Lattice parameters were: a = 11.657(2), b = 17.237(2), c = 12.764(2) ?, β = 98.735(14)°, 2535.0(7) ?
基金Project(50834003)supported by the National Natural Science Foundation of ChinaProject(09JK561)supported by Educational Commission of Shaanxi Province of China
文摘High dispersive copper nanoparticles were prepared by chemical reduction method using potassium borohydride as reducing agent.The effects of reactant ratio,concentration of CuSO4,reaction temperature,and dispersant on the size of product and conversion rate were studied.The morphologies of copper nanoparticles were characterized by scanning electron microscopy.The results show that the optimum process conditions are as follows:the molar ratio of KBH4 to CuSO4 is 0.75(3:4),concentration of CuSO4 is 0.4 mol/L,reaction temperature is 30℃,and dispersant is n-butyl alcohol.The average particles size of copper powders with spherical shape gained is about 100 nm.
基金supported by the Key Project of Chinese Ministry of Education (No. 208076)Shandong Provincial Natural Science Foundation,China (No. ZR2010EM069)the Open Project of State Key Laboratory of Chemical Resource Engineering,Beijing University of Chemical Technology
文摘Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH 4) for hydrogen generation.At solution temperature of 0 C,the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate,which makes it suitable for applications under the circumstance of low environmental temperature.The byproduct of methanolysis reaction is analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct,NaB(OCH 3) 4.The catalytic activity of Co/Al2O3 towards NaBH 4 methanolysis can be further improved by appropriate calcination treatment.The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.
基金National Natural Science Foundation of China(No.20336010)National Basic Research Programme of China(No.2003CB716008)
文摘Ionic liquids(ILs) are attracting much attention in various fields of chemical synthesis, electrochemical applications, liquid-liquid extractions, as well as biotransformations. Among those fields, the application of ILs as the potential green solvent for a wide variety of synthetic processes is an area of intense researches. High yield, high selectivity, and good catalytic charac-teristics have usually been achieved. After the isolation of products, ILs can usually be recovered and recycled many times by simple treating procedures, such as, filtration, extraction, and dryness.
基金part of the activities of SCCER HeE, which is financially supported by Innosuisse – Swiss Innovation Agency
文摘Stability of borohydrides is determined by the localization of the negative charge on the boron atom.Ionic liquids(ILs) allow to modify the stability of the borohydrides and promote new dehydrogenation pathways with a lower activation energy. The combination of borohydride and IL is very easy to realize and no expensive rare earth metals are required. The composite of the ILs with complex hydrides decreases the enthalpy and activation energy for the hydrogen desorption. The Coulomb interaction between borohydride and IL leads to a destabilization of the materials with a significantly lower enthalpy for hydrogen desorption. Here, we report a simple ion exchange reaction using various ILs, such as vinylbenzyltrimethylammonium chloride([VBTMA][Cl]), 1-butyl-3-methylimidazolium chloride([bmim][Cl]), and 1-ethyl-1-methylpyrrolidinium bromide([EMPY][Br]) with NaBH4 to decrease the hydrogen desorption temperature. Dehydrogenation of 1-butyl-3-methylimidazolium borohydride([bmim][BH4]) starts below 100℃. The quantity of desorbed hydrogen ranges between 2.4 wt% and 2.9 wt%, which is close to the theoretical content of hydrogen. The improvement in dehydrogenation is due to the strong amine cation that destabilizes borohydride by charge transfer.
文摘PtRuIn/C electrocatalysts( 20% metal loading by weight) were prepared by sodium borohydride reduction process using H_2PtCl6·6H_2O,RuCl_3·xH_2O and InCl_3·xH_2O as metal sources,borohydride as reducing agent and Carbon Vulcan XC72 as support. The synthetized PtRuIn/C electrocatalysts were characterized by X-ray diffraction( XRD),energy dispersive analysis( EDX),transmission electron microscopy( TEM),cyclic voltammetry( CV),chronoamperommetry( CA) and polarization curves in alkaline and acidic electrolytes( single cell experiments). The XRD patterns showPtpeaks are attributed to the face-centered cubic( fcc) structure,and a shift of Pt( fcc) peaks indicates that Ru or In is incorporated into Ptlattice. TEMmicrographs showmetal nanoparticles with an average nanoparticle size between 2.7 and 3.5 nm. Methanol oxidation in acidic and alkaline electrolytes was investigated at room temperature,by CV and CA. PtRu/C( 50 ∶ 50) shows the highest activity among all electrocatalysts in study considering methanol oxidation for acidic and alkaline electrolyte. Polarization curves at 80 ℃ showPtRuIn/C( 50 ∶ 25 ∶ 25)with superior performance for methanol oxidation,when compared to Pt/C,PtIn/C and PtRu/C for both electrolytes. The best performance obtained by PtRuIn/C( 50 ∶ 25 ∶ 25) in real conditions could be associated with the increased kinetics reaction and/or with the occurrence simultaneously of the bifunctional mechanism and electronic effect resulting from the presence of Ptalloy.
基金The project was supported by the FAPESP(2014/09087-4,2014/50279-4).
文摘The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
文摘Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hydrogen and enhance the utilization of borohydride, Ti/Zr metal powders has been added into the parent LmNi4.78Mn0.22 (where Lm is La-richened mischmetal) alloy (LNM) by ball milling and heat treatment methods. It is found that the addition of Ti/Zr metal powders lowers the electrochemical catalytic activity of the electrodes, at the same time, restrains the generation of hydrogen and enhances the utilization of the fuel. All the results show that the hydrogen generation rate or the utilization of the fuel is directly relative to the electrochemical catalytic activity or the discharge capability of the electrodes. The utilization of the fuel increases with discharge current density. It is very important to find a balance between the discharge capability and the utilization of the fuel.
基金support of this work from the Research Council of Mazandaran University gratefully acknowledged.
文摘A simple and convenient procedure for the preparation of amines from aldehydes and ketones with sodium borohydride activated by silica chloride as a catalyst under solvent-free conditions is described.A variety of aliphatic and aromatic aldehydes,ketones and amines when mixed with NaBH;/silica chloride at room temperature,afforded excellent yield of the corresponding amines.
基金Funded by the Ministry of Science and Technology(MOST)of China(No.2018YFB1502104)the National Natural Science Foundation of China(No.21771006)the Equipment Development Department of People’s Republic of China Central Military Commission(Pre-research Project of the Thirteenth FiveYear Plan)(No.41421020103)。
文摘We reported an inexpensive and high-efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt%based on all the reactants can be achieved with excellent hydrogen generation kinetics.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB808200)the National Natural Science Foundation of China (Grant Nos. 51032001,11074090,10979001,and 51025206)the Funds for Changjiang Scholar and Innovative Research Team in University (Grant No. IRT1132)
文摘The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg(BH4)2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. It is found that the ambient pressure phases of meta-stable I41/amd and unstable P-3ml proposed recently are extra stable and cannot decompose under high pressure. Enthalpy calculation indicates that the ground state of F222 structure proposed by Zhou et al. [2009 Phys. Rev. B 79 212102] will transfer to I41/amd at 0.7 GPa, and then to a P-3ml structure at 6.3 GPa. The experimental P6122 structure (a-phase) transfers to I41/amd at 1.2 GPa. Furthermore, both I41/arnd and P-3ml can exist as high volumetric hydrogen density phases at low pressure. Their theoretical volumetric hydrogen densities reach 146.351 g H2/L and 134.028 g H2/L at ambient pressure, respectively. The calculated phonon dispersion curve shows that the I41/amd phase is dynamically stable in a pressure range from 0 to 4 CPa and the P-3ral phase is stable at pressures higher than 1 GPa. So the I41/arnd phase may be synthesized under high pressure and retained to ambient pressure. Energy band structures show that they are both always ionic crystalline and insulating with a band-gap of about 5 eV in this pressure range. In addition, they each have an anisotropic compressibility. The c axis of these structures is easy to compress. Especially, the c axis and volume of P-3ml phase are extraordinarily compressible, showing that compression along the e axis can increase the volumetric hydrogen content for both I41/amd and P-3ml structures.
基金Funded by the Ministry of Science and Technology(MOST)of China(No.2018YFB1502104)the Natural Science Foundation of China(No.21771006)the Equipment Development Department of People’s Republic of China Central Military Commission(Preresearch Project of the Thirteenth Five-Year Plan,No.41421020103)。
文摘We reported a low cost,high efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt% based on all the reactants can be achieved with excellent hydrogen generation kinetics.
基金the Ministry of Education,Science and Technological Development of Republic of Serbia for support within project no.451–03–68/2020–14/200146Funda??o para a Ciência e a Tecnologia(FCT,Portugal)for contract no.IF/01084/2014/CP1214/CT0003 under IF2014 Programme(D.M.F.Santos)and no.IST-ID/156–2018(B.?ljuki?)+1 种基金sponsored in part by the NATO Science for Peace and Security Programme under grant G5729(I.A.Pa?ti and B.?ljuki?)the support from the Carl Tryggers Foundation for Scientific Research(grant no.18:177)。
文摘Problems associated with carbon support corrosion under operating fuel cell conditions require the identification of alternative supports for platinum-based nanosized electrocatalysts.Platinum supported on manganese vanadate(Pt/MnV_(2)O_(6))was prepared by microwave irradiation method and characterized using X-ray diffraction,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy with energy dispersive spectroscopy,and transmission electron microscopy.The borohydride oxidation reaction(BOR)on Pt/MnV_(2)O_(6) was studied in highly alkaline media using voltammetry,chronoamperometry,and electrochemical impedance spectroscopy.BOR electrocatalytic activity of Pt/MnV_(2)O_(6) was also compared with that of commercial Pt/C(46 wt%Pt)electrocatalyst.The apparent activation energy of BOR at Pt/MnV_(2)O_(6) was estimated to be 32 k J mol^(-1) and the order of reaction to be 0.51,indicating that borohydride hydrolysis proceeds in parallel with its oxidation.Long-term stability of Pt/MnV_(2)O_(6) under BOR typical conditions was observed.A laboratory-scale direct borohydride fuel cell assembled with a Pt/MnV_(2)O_(6) anode reached a specific power of 274 W g^(-1).Experimental results on Pt/MnV_(2)O_(6) were complemented by DFT calculations,which indicated good adherence of Pt to MnV_(2)O_(6),beneficial for electrocatalyst stability.
文摘It was established that application of bipolar membrane in a direct borohydride fuel cell (DBFC) with H2O2 co-generation enabled to keep constant pH in catholyte within 2.5 - 3.2 limits, which allowed us to carry out treatment of water polluted by organic compounds in fuel cell catholyte. Treatment of water was carried out by electro-Fenton and photo-electro-Fenton methods. With the view of efficiency, photo-electro-Fenton method of treatment was the most efficient, which enabled to decrease COD of catholytes containing (in each case) phenol, valsaren, 400 g/L dymethoate (BI-58) and valsaciper from 500 ppm to 30, 11, 9 and 3 ppm, respectively after 180 min treatment. By increasing the catholyte temperature from 20℃?to 40℃?in the same period, phenol COD fell to 5 ppm.
基金the National Natural Science Foundation of China (No.29977014).
文摘A new chitosan-supported borohydride reducing reagent (CBER) was prepared by treatment of KBH4 with the resin of chitosan derivative, which was first synthesized from: the reaction of cross-linked chitosan microsphere with glycidyl trimethylammonium chloride. CBER could reduce aromatic carbonyl compound to corresponding alcohol.
文摘Aromatic nitro compounds are reduced to correspouding amiues in ethanol by borohydride exchauge resin(BER)in the presence of transition metal Pd,Co,Ni,Cu)compounds as catalysts.
文摘A highly efficient and facile protocol for the selective reduction of carboxylic acid of Fenofibric acid to corresponding alcohol was developed. The selective reduction was carried out by activation of carboxylic acid by mixed anhydride followed by the reaction of sodium borohydride in presence of methanol. This is the first example of chemoselective reduction of carboxylic acid to alcohol in presence of a ketone without any external catalyst or ligand in a single step. The reaction offers wide applicability for the selective carboxylic group reduction methodology. The chemoselective reduction was demonstrated by the reduction of Fenofibric acid, an active metabolite of the drug Fenofibrate, to corresponding alcohol in excellent selectivity, yield, and purity.