Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/22—Fuel cells in which the fuel is based on materials comprising carbon or oxygen or hydrogen and other elements; Fuel cells in which the fuel is based on materials comprising only elements other than carbon, oxygen or hydrogen
  • H01M8/225—Fuel cells in which the fuel is based on materials comprising particulate active material in the form of a suspension, a dispersion, a fluidised bed or a paste
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04186—Arrangements for control of reactant parameters, e.g. pressure or concentration of liquid-charged or electrolyte-charged reactants
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04201—Reactant storage and supply, e.g. means for feeding, pipes
  • H01M8/04216—Reactant storage and supply, e.g. means for feeding, pipes characterised by the choice for a specific material, e.g. carbon, hydride, absorbent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/08—Fuel cells with aqueous electrolytes
  • H01M8/083—Alkaline fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present invention relates to hydride-containing fuel compositions for direct and indirect liquid fuel cells.
• Fuel cells are electrochemical power sources wherein electrocatalytic oxidation of a fuel (e.g., molecular hydrogen or methanol) at an anode and electrocatalytic reduction of an oxidant (often molecular oxygen) at a cathode take place simultaneously.
• a fuel e.g., molecular hydrogen or methanol
• an oxidant often molecular oxygen
• Conventional fuels such as hydrogen and methanol pose several storage and transportation problems, in particular, for portable fuel cells (e.g., for use with portable electric and electronic devices such as laptops, cell phones, and the like).
• Borohydride (and other hydride) based fuels are of particular interest for portable fuel cells, due to their very high specific energy capacity (see, e.g., J. of Electrochem. Soc, 150, (3), A398-402, 2003).
• a starting material such as, e.g., a borohydride compound is converted to an anodic oxidation product such as, e.g., a metaborate.
• the solubility of the starting material and that of the oxidation product in the liquid phase of the fuel may differ substantially. This difference in solubility may affect the fuel efficiency and thus, the performance of the fuel cell.
• NaBH 4 has a relatively high solubility in an alkaline solution whereas its oxidation product, NaBO 2 , is less soluble in this solution.
• the present invention provides a hydride containing fuel composition for a liquid fuel cell.
• the composition comprises an alkaline liquid phase and at least a first hydride compound and a second hydride compound.
• the solubility of the first hydride compound in the liquid phase is higher than the solubility of the second hydride compound in the liquid phase and the solubility of the anodic oxidation product of the first hydride compound in the liquid phase is lower than the solubility of the anodic oxidation product of the second hydride compound in the liquid phase.
• the molar ratio of the first hydride compound and the second hydride compound may be from about 95 : 5 to about 5 : 95, e.g., from about 90 : 10 to about 10 : 90, from about 80 : 20 to about 20 : 80, from about 75 : 25 to about 25 : 75, or from about 60 : 40 to about 40 : 60.
• the composition may comprise hydride compounds in a total concentration of at least about 0.5 mole per liter of composition, e.g., in a total concentration of at least about 1 mole per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter of composition.
• concentration of the hydride compounds may as high as, e.g., at least about 6 moles per liter, at least about 8 moles per liter, or at least about 10 moles per liter of composition.
• the liquid phase of the composition may comprise hydroxide ions.
• the hydroxide ions may be present in a concentration of at least about 0.01 mole per liter, e.g., at least about 0.05 mole per liter, at least about 0.1 mole per liter, at least about 0.5 mole per liter, at least about 1 mole per liter, at least about 1.5 moles per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter and/or in a concentration that is not higher than about 7 moles per liter of liquid phase.
• the hydroxide ion concentration may even be higher, e.g., up to about 14 moles per liter, e.g., up to about 12 moles per liter.
• the liquid phase may comprise at least one hydroxide ion providing compound dissolved therein, said hydroxide ion providing compound being selected from hydroxides of alkali metals, alkaline earth metals, Zn and Al, and from ammonium hydroxide, e.g., from one or more of LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Mg(OH) 2 , Ba(OH) 2 , Zn(OH) 2 , AI(OH) 3 and NH 4 OH.
• the liquid phase may comprise dissolved therein NaOH and/or KOH.
• liquid phase may comprise one or more of water, methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1 ,2,4- butanetriol, trimethylol propane, pentaerythritol, sorbitol (or any other sugar alcohol), glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxan, tetrahydrofuran, diglyme, triglyme, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine and tripropanolamine.
• the liquid phase may comprise water, either alone or in combination with one or more substances selected from (cyclo)aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C 2-4 alkylene glycols, di(C 2-4 alkylene glycols), poly(C 2 - 4 alkylene glycols), ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), di-Ci -4 -alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), ethylene oxide/propylene oxide block copolymers, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, ethoxylated and propoxylated aliphatic polyols, aliphatic ethers having up to about 6 carbon atoms and up to about 6
• the present invention also provides a hydride containing fuel composition for a liquid fuel cell, which composition comprises an alkaline liquid phase and at least a first hydride compound and a second hydride compound.
• the solubility of the first hydride compound in the liquid phase is higher than the solubility of the second hydride compound in the liquid phase and the solubility of the anodic oxidation product of the first hydride compound in the liquid phase is lower than the solubility of the anodic oxidation product of the second hydride compound in the liquid phase.
• the alkaline liquid phase further has a hydroxide ion concentration of at least about 0.5 mole per liter and comprises dissolved therein one or more of LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Mg(OH) 2 , Ba(OH) 2 , Zn(OH) 2 , AI(OH) 3 and NH 4 OH.
• the first hydride compound and the second hydride compound are independently selected from NaBH 4 , KBH 4 , LiBH 4 , NH 4 BH 4 , Be(BH 4 ) 2 , Ca(BH 4 ) 2 , Mg(BH 4 ) 2 , Zn(BH 4 ) 2 , AI(BH 4 ) 3 , polyborohydrides, (CHs) 2 NHBH 3 , NaCNBH 3 , LiH, NaH, KH, CaH 2 , BeH 2 , MgH 2 , NaAIH 4 ,
• the first hydride compound and the second hydride compound may independently be selected from NaBH 4 , KBH 4 , LiBH 4 , Be(BH 4 ) 2 , NH 4 BH 4 , a polyborohydride, Ca(BH 4 ) 2 , Mg(BH 4 ) 2 , Zn(BH 4 ) 2 , AI(BH-O 3 , (CH 3 ) 2 NHBH 3 and NaCNBH 3 .
• the first hydride compound and the second hydride compound may be NaBH 4 and KBH 4 .
• the molar ratio of the first hydride compound and the second hydride compound may be from about 95 : 5 to about 5 : 95, e.g., from about 75 : 25 to about 25 : 75.
• the composition may comprise the hydride compounds in a total concentration of at least about 0.5 mole per liter of composition, e.g., in a total concentration of at least about 1 mole per liter, at least about 2 moles per liter, or at least about 3 moles per liter of composition.
• the hydroxide ion concentration in the liquid phase may be at least about 1 mole per liter, e.g., at least about 1.5 moles per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter and/or may be not higher than about 7 moles per liter.
• the liquid phase may comprise dissolved therein NaOH and/or KOH.
• the liquid phase may comprise at least one, e.g., at least two, solvents selected from water, (cyclo)aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C 2-4 alkylene glycols, di(C 2-4 alkylene glycols), poly(C 2-4 alkylene glycols), mono-Ci ⁇ -alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), di-Ci -4 -alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), ethylene oxide/propylene oxide block copolymers, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, ethoxylated and propoxylated aliphatic polyols,
• the liquid phase may comprise water.
• the liquid phase may comprise water and one or more of methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1 ,2,4-butanetriol, trimethylolpropane, pentaerythritol, sorbitol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxan, tetrahydrofuran, diglyme, triglyme, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine and tripropanolamine.
• the present invention also provides a hydride containing mixture for use in a fuel for a liquid fuel cell, which mixture comprises at least a first hydride compound and a second hydride compound, which compounds are independently selected from hydrides, borohydrides (including polyborohydrides and cyanoborohydrides) and aluminum hydrides of alkali and alkaline earth metals, Zn, Al, ammonium and dialkylamines and wherein the molar ratio of the first hydride compound and the second hydride compound is from about 95 : 5 to about 5 : 95.
• the molar ratio of the hydride compounds may be from about 80 : 20 to about 20 : 80.
• the present invention also provides a hydride containing fuel composition for a direct liquid fuel cell, which composition comprises at least two different hydride compounds.
• the at least two different hydride compounds are selected such that the composition provides, under otherwise identical circumstances, a higher fuel efficiency than an otherwise identical fuel composition that comprises only one of these different hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds. In other words, there is a synergism.
• the first hydride compound and/or the second hydride compound may be selected from borohydrides, e.g., from borohydrides of alkali and alkaline earth metals.
• at least one of the first hydride compound and the second hydride compound may be NaBH 4 or KBH 4 .
• the molar ratio of the first hydride compound and the second hydride compound may be from about 95 : 5 to about 5 : 95, e.g., from about 90 : 10 to about 10 : 90, from about 80 : 20 to about 20 : 80, from about 75 : 25 to about 25 : 75, or from about 60 : 40 to about 40 : 60.
• the firSt "M'ydrl l cl'e u tbm'(D6 ⁇ niici '' 1 ari ⁇ /or the second hydride compound may be selected from borohydrides, e.g., from borohydrides of alkali and alkaline earth metals.
• the first hydride compound and/or the second hydride compound may be NaBH 4 or KBH 4 .
• the molar ratio of the first hydride compound and the second hydride compound may be from about 95 : 5 to about 5 : 95, e.g., from about 90 : 10 to about 10 : 90, from about 80 : 20 to about 20 : 80, from about 75 : 25 to about 25 : 75, or from about 60 : 40 to about 40 : 60.
• the present invention also provides a hydride containing fuel composition for a liquid fuel cell, which composition comprises an alkaline liquid phase and one or more hydride compounds.
• the one or more hydride compounds are dissolved in the liquid phase (e.g., at about room temperature) in a total concentration of at least about 0.5 mole per liter of liquid phase and the solubility of the anodic oxidation products of the one or more hydride compounds in the liquid phase at about room temperature (e.g., at about 25 0 C) is such that after an anodic oxidation of about 80 mole-% of the one or more hydride compounds substantially no oxidation products precipitate (at about room temperature).
• substantially no precipitate as used herein and in the appended claims is intended to mean less than about 10 %, preferably less than about 5 %, e.g., less than about 1 % of the formed anodic oxidation product is present in undissolved form.
• substantially no oxidation products precipitate after an anodic oxidation of about 90 mole-%, or even after an anodic oxidation of about 95 mole-% of the one or more hydride compounds and/or the one or more hydride compounds may be dissolved in the liquid phase in a total concentration of at least about 1 mole per liter, e.g., in a total concentration of at least about 2 moles per liter, or at least about 3 moles per liter.
• the one or more hydride compounds may independently be selected from hydrides, borohydrides and aluminum hydrides of alkali and alkaline earth metals, Zn, Al, ammonium and dialkylamines, for example, from NaBH 4 , KBH 4 , LiBH 4 , Be(BH 4 ) 2 , NH 4 BH 4 , a polyborohydride, Ca(BH 4 ) 2 , Mg(BH 4 ) 2 , Zn(BH 4 ) 2 , AI(BH 4 ) 3 , (CH 3 ) 2 NHBH 3 and NaCNBH 3 .
• the one or more hydride compounds may selected from (poly)borohydrides, e.g., from borohydrides of alkali and alkaline earth metals.
• at least one of the one or more hydride compounds may be selected from NaBH 4 and KBH 4 .
• the one or more hydride compounds may comprise at least a first hydride compound and a second hydride compound and the solubility of the first hydride compound in the liquid phase may be higher than the solubility of the second hydride compound in the liquid phase and the solubility of the anodic oxidation product of the first hydride compound in the liquid phase may be lower than the solubility of the anodic oxidation product of the second hydride compound in the liquid phase.
• the molar ratio of the first hydride compound and the second hydride compound may be from about 95 : 5 to about 5 : 95, e.g., from about 90 : 10 to about 10 : 90, from about 80 : 20 to about 20 : 80, from about 75 : 25 to about 25 : 75, or from about 60 : 40 to about 40 : 60.
• the liquid phase may comprise hydroxide ions in a concentration of at least about 1 mole per liter, e.g., in a concentration of at least about 1.5 moles per liter, at least about 2 moles per liter and/or in a concentration of not higher than about 7 moles per liter.
• the liquid phase may comprise at least one hydroxide ion providing compound dissolved therein, said hydroxide ion providing compound being selected from hydroxides of alkali metals, alkaline earth metals, Al and Zn and from ammonium hydroxide, such as, e.g., LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Mg(OH) 2 , Ba(OH) 2 , Zn(OH) 2 , AI(OH) 3 , and NH 4 OH.
• the liquid phase may comprise dissolved therein NaOH and/or KOH.
• the liquid phase may comprise at least one (e.g., at least two) of water, (cyclo)aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C 2-4 alkylene glycols, di(C 2-4 alkylene glycols), poly(C 2-4 alkylene glycols), mono-Ci -4 -alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), di-C 1-4 -alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), ethylene oxide/propylene oxide block copolymers, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, ethoxylated and propoxylated aliphatic polyol
• the liquid phase may comprise water, alone or in combination with one or more solvents selected from (cyclo)aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C 2-4 alkylene glycols, di(C 2- 4 alkylene glycols), poly(C 2-4 alkylene glycols), mono-C-u-alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and PoIy(C 2-4 alkylene glycols), di-C-u-alkyl ethers of C 2-4 alkylene glycols, di(C 2-4 alkylene glycols) and poly(C 2-4 alkylene glycols), ethylene oxide/propylene oxide block copolymers, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, ethoxylated and propoxylated aliphatic polyols, aliphatic ethers
• the liquid phase may comprise water and one or more (e.g., two) of methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1 ,2,4-butanetriol, trimethylolpropane, pentaerythritol, sorbitol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxan, tetrahydrofuran, diglyme, triglyme, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine and tripropanolamine, e.g., water and at least one of methanol, ethanol, propanol, isopropanol and ethylene glycol.
• methanol, ethanol, propanol, isopropanol and ethylene glycol e.g., water and at
• the present invention also provides a liquid fuel cell which comprises a fuel composition of the present invention, including the various aspects thereof.
• the present invention also provides a fuel cartridge for (re)filling a liquid fuel cell, which cartridge comprises a fuel composition of the present invention, including the various aspects thereof.
• the present invention also provides a method of increasing the fuel efficiency of a hydride compound containing liquid fuel composition for a direct liquid fuel cell.
• This method comprises selecting one or more hydride compounds and one or more solvents such that the one or more hydride compounds are soluble in the one or more solvents in a concentration of at least about 0.5 mole per liter (at about room temperature) and that after an anodic oxidation of about 80 mole-% of the one or more hydride compounds substantially all formed anodic oxidation products are soluble in the one or more solvents (at about room temperature).
• the one or more hydride compounds may comprise at least a first hydride compound and a second hydride compound and the solubility of the first hydride compound in the one or more solvents may be higher than the solubility of the second hydride compound in the one or more solvents and the solubility of the anodic oxidation product of the first hydride compound in the one or more solvents may be lower than the solubility of the anodic oxidation product of the second hydride compound in the one or more solvents.
• the present invention also provides a method for increasing the fuel efficiency of a hydride compound containing liquid fuel composition for a direct liquid fuel cell, which method comprises the employment of at least two different hydride compounds (e.g., at least two different borohydride compounds) in the fuel composition.
• the at least two (e.g., two, three or four) different hydride compounds are selected such that a fuel composition comprising these different hydride compounds, under otherwise identical conditions, has a higher efficiency than an otherwise identical fuel composition which comprises only one of the at least two different hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds.
• the at least two hydride compounds may be present in the liquid phase of the fuel composition in a total concentration of at least about 1 mole per liter, e.g., at least about 2 moles per liter.
• the present invention also provides a method for improving the performance of a liquid fuel cell which comprises a hydride compound containing liquid fuel composition.
• the method comprises the employment of at least two different hydride compounds (e.g., two or more different borohydride compounds) in the liquid fuel composition, the at least two different hydride compounds being selected such that under otherwise identical conditions the fuel composition comprising the at least two different hydride compounds is chemically less aggressive toward at least one structural component of the fuel cell (e.g., the anode) than, and shows at least the same efficiency as a liquid fuel composition which comprises only one of these hydride compounds in a iti ⁇ la'raniO'U ⁇ ifwIil ⁇ hl' i& rdefitical with a total molar amount of the at least two different hydride compounds.
• at least two different hydride compounds e.g., two or more different borohydride compounds
• the performance of a fuel for a liquid fuel cell may be optimized by providing a relatively high initial concentration of dissolved (boro)hydride compound(s) while at the same time preventing the precipitation of substantial amounts of anodic oxidation products and/or while preventing any significant damage to the structural components of the fuel cell, in particular the anode, caused be a chemically too aggressive fuel.
• the present invention employs several basic concepts which can be used individually or in combination.
• the solubilities of the hydride compounds and the anodic reaction products may be similar or different, as long as the solvent mixture can dissolve both the hydride compounds and the anodic oxidation products thereof to a desirable high extent.
• a third concept balances the concentrations of the various (metal) cations in the liquid phase of the fuel (which may be a suspension) in order to achieve a desirable high (boro)hydride concentration in the liquid phase of the fuel while at the same time keeping the chemical aggressiveness of the fuel at acceptable levels.
• the "efficiency" of a fuel may be assessed by using various parameters, e.g., the initial current that is obtainable or the electric output per volume unit, each determined in a fuel cell.
• the hydride compounds for use in the present invention preferably are compounds which can be oxidized as such at the anode of a fuel cell to provide electrons.
• the term "hydride compound” as used in the present specification and the appended claims is used in a broad sense and encompasses, in particular, compounds which are "simple" hydrides, such as, e.g., NaH, KH, etc. as well as compounds which comprise a hydride complex ion such as, e.g., borohydride, aluminum hydride and the like.
• Non-limiting examples of metal hydride compounds for use in the present invention include hydrides, borohydrides, including cyanoborohydrides and poyborohydrides, and aluminum hydrides of alkali metals such as, e.g., Li, Na, K, Rb and Cs, and alkaline earth metals such as, e.g., Be, Mg, Ca, Sr and Ba, but also of other metals such as Al and Zn, ammonium and complexes of BH 3 and mono-, di-, trialkylamines.
• alkali metals such as, e.g., Li, Na, K, Rb and Cs
• alkaline earth metals such as, e.g., Be, Mg, Ca, Sr and Ba
• other metals such as Al and Zn, ammonium and complexes of BH 3 and mono-, di-, trialkylamines.
• Non-limiting examples of polyborohydrides are those of formulae MB 3 H 8 , M 2 B 10 Hi 0 , MBi 0 H 13 , M 2 Bi 2 Hi 2 and M 2 B 20 H 18 wherein M may be Li, Na, K, NH 4 , Be-i /2 , Ca 1Z2 , Mg-i/ 2 , Zn 1Z2 or AIv 3 (the fractions associated with Ca, Mg, Zn and Al take into account that these metals are bi- or trivalent).
• Further examples of polyborohydride compounds which are suitable for use in the present invention are disclosed in, e.g., U.S. Patent Application Publication 2005/0132640 A1 , the entire disclosure whereof is incorporated by reference herein. Borohydrides and, in particular, NaBH 4 and KBH 4 are examples of preferred hydrides for the purposes of the present invention.
• the liquid phase of the compositions of the present invention preferably comprises one or more polar (protic and/or aprotic) solvent components. If the solvent is a pure solvent, i.e., there is only one solvent, the solvent is preferably polar. If the solvent is a solvent mixture, i.e., comprises one or more (e.g., two, three, four, or even more) individual solvents, at least one of the components of the mixture is preferably polar. For example, all or at least substantially all of the solvent components may be polar. Solvents and solvent mixtures for use in the present invention preferably are liquid at room temperature and are preferably present in an amount which is sufficient to dissolve the hydride compound(s) and hydroxide ion providing compound(s).
• Non- limiting exIMplesisf&dita ⁇ i' solvent components include water, mono- and polyhydric alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, glycerol, 1 ,2,4- butanetriol, trimethylolpropane and pentaerythritol) and mono- and polyalkylene glycols (such as, e.g., ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol), aliphatic esters of mono- and polycarboxylic acids (e.g., ethyl acetate, methyl acetate, ethyl formiate, and diethyloxalate), aliphatic ketones (such as, e.g., acetone, methyl ethyl ketone, and diethylketone), aliphatic aldehydes (such as, acetaldehyde and
• a preferred solvent component is water.
• examples of other preferred solvent components include monohydric and polyhydric aliphatic and cycloaliphatic alcohols such as methanol and ethanol. If water is present, the concentration thereof will often be at least about 10 % by volume, e.g., at least about 30 % by volume, at least about 50 % by volume, or at least about 70 % by volume, based on the total volume of the combined solvents.
• the hydroxide ion providing compounds for use in the compositions of the present invention may be any compounds which are capable of providing hydroxide ions in the composition, e.g., by dissociation, decomposition, or by (in situ) reaction or interaction with any other compound that may be present in the composition. Of course, these compounds must not interfere to any significant extent with the operation of the fuel cell and, in particular, the electrochemical reactions that take place therein.
• the hydroxide ion providing compound will include at least one alkali or alkaline earth metal hydroxide and/or ammonium hydroxide.
• the molar ratio of these hydride compounds will usually be in the range of from about 99 : 1 to about 1 : 99, particularly in the range of from about 95 : 5 to about 5 : 95. Often the molar ratio will be not higher than about 90 : 10, e.g. not higher than about 80 : 20, not higher than about 75 : 25, or not higher than about 60 : 40, and not lower than about 10
• a molar ratio of NaBH 4 and KBH 4 of about 25 : 75 may afford particularly advantageous results.
• a hydroxide ion providing compound such as NaOH
• this compound will also be present in dissociated form in the liquid phase, thereby increasing the concentration of sodium cations relative to potassium cations in the liquid phase and, consequently, increasing the concentration of NaBH 4 relative to that of KBH 4 .
• NaBH 4 is employed as the only borohydride compound and KOH is employed as the only hydroxide ion providing compound
• a corresponding solution would contain not only NaBH 4 , but also KBH 4 .
• the properties of a corresponding solution (fuel) are determined, inter alia, by the relative proportions of all (metal) cations which are present in the solution, i.e., not only the relative proportions in which these cations are present in the employed hydride compounds.
• a fuel composition of the present invention comprises one or more hydride compounds in a total concentration of at least about 0.5 mole per liter of composition (the composition including a liquid phase and an optionally present solid phase of undissolved material), e.g., in a total concentration of at least about 1 mole per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter of liquid phase.
• concentration may even be higher, especially in the case of fuel concentrates.
• the liquid phase of a fuel composition of the present invention preferably comprises hydroxide ions in a concentration of at least about 0.01 mole per liter, e.g., about 0.05 mole per liter, about 0.1 mole per liter, about 0.5 mole per liter, at least about 1 mole per liter, at least about 1.5 moles per liter, at least about 2 moles per liter, at least about 3 moles per liter, or even at least about 6 moles per liter.
• the hydroxide ion concentration is preferably not higher than about 8 moles per liter, e.g., not higher than about 7 moles per liter.
• the hydrbxide ⁇ bff'c ⁇ nde ⁇ tration will often be higher than about 7 moles per liter, e.g., up to about 14 moles per liter, or up to about 12 moles per liter.
• compositions of the present invention may optionally comprise various other components whose presence in the fuel may be desirable, at least as long as these other components do not significantly interfere with the intended use of the fuel composition.
• the compositions may comprise additives such as, e.g., stabilizers.
• Preferred stabilizers include aliphatic and aromatic amines.
• Fig. 2 shows a discharge curve in a direct borohydride - air fuel cell of the fuel prepared according to Example 2;
• Fig. 3 shows a discharge curve in a direct borohydride - air fuel cell of the fuel prepared according to Example 3.
• Fig. 4 shows a discharge curve in a direct borohydride - air fuel cell of the fuel prepared according to Example 4.
• a fuel of the following composition (in % by weight) is prepared: water" 68 %
• a fuel of the following composition (in % by weight) is prepared:
• a fuel of the following composition (in % by weight) is prepared:
• a fuel of the following composition (in % by weight) is prepared:

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• 2006
  • 2006-03-21 US US11/384,364 patent/US20060213119A1/en not_active Abandoned
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