Fuel composition for fuel cells

Abstract

A hydride containing fuel composition for a liquid fuel cell. The composition comprises an alkaline liquid phase and at least two hydride compounds. The solubility of the first hydride compound in the liquid phase is higher than the solubility of a second hydride compound in the liquid phase and the opposite is true for the anodic oxidation products thereof. This Abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

1 . A hydride containing fuel composition for a liquid fuel cell, wherein the composition comprises an alkaline liquid phase and at least a first hydride compound and a second hydride compound and wherein a solubility of the first hydride compound in the liquid phase is higher than a solubility of the second hydride compound in the liquid phase and a solubility of an anodic oxidation product of the first hydride compound in the liquid phase is lower than a solubility of an anodic oxidation product of the second hydride compound in the liquid phase.  
   
   
       2 . The fuel composition of  claim 1 , wherein the first hydride compound and the second hydride compound are independently selected from hydrides, borohydrides and aluminum hydrides of alkali and alkaline earth metals, ammonium, Zn and Al.  
   
   
       3 . The fuel composition of  claim 1 , wherein 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 , Al(BH 4 ) 3 , polyborohydrides, (CH 3 ) 3 NBH 3 , NaCNBH 3 , LiH, NaH, KH, CaH 2 , BeH 2 , MgH 2 , NaAlH 4 , LiAlH 4  and KAlH 4 .  
   
   
       4 . The fuel composition of  claim 3 , wherein the first hydride compound and the second hydride compound are independently selected from NaBH 4 , KBH 4 , LiBH 4 , NH 4 BH 4  and polyborohydrides of formula MB 3 H 8 , M 2 B 10 H 10 , MB 10 H 13 , M 2 B 12 H 12  or M 2 B 20 H 18  wherein M=Li, Na, K, NH 4 , Be 1/2 , Ca 1/2 , Mg 1/2 , Zn 1/2  or Al 13 .  
   
   
       5 . The fuel composition of  claim 1 , wherein at least one of the first hydride compound and the second hydride compound is selected from borohydrides and polyborohyd rides.  
   
   
       6 . The fuel composition of  claim 5 , wherein the first hydride compound and the second hydride compound are selected from borohydrides and polyborohydrides of alkali and alkaline earth metals.  
   
   
       7 . The fuel composition of  claim 5 , wherein at least one of the first hydride compound and the second hydride compound is NaBH 4  or KBH 4 .  
   
   
       8 . The fuel composition of  claim 1 , wherein a molar ratio of the first hydride compound and the second hydride compound is from about 95:5 to about 5:95.  
   
   
       9 . The fuel composition of  claim 8 , wherein the molar ratio is from about 60:40 to about 40:60.  
   
   
       10 . The fuel composition of  claim 1 , wherein the composition comprises hydride compounds in a total concentration of at least about 0.5 mole per liter of composition.  
   
   
       11 . The fuel composition of  claim 10 , wherein the total concentration is at least about 3 moles per liter of composition.  
   
   
       12 . The fuel composition of  claim 1 , wherein the liquid phase comprises hydroxide ions.  
   
   
       13 . The fuel composition of  claim 12 , wherein a hydroxide ion concentration in the liquid phase is at least about 0.01 mole per liter.  
   
   
       14 . The fuel composition of  claim 13 , wherein the hydroxide ion concentration is at least about 0.1 mole per liter.  
   
   
       15 . The fuel composition of  claim 1 , wherein the liquid phase comprises at least one hydroxide ion providing compound dissolved therein, said hydroxide ion providing compound being selected from alkali and alkaline earth metal hydroxides and ammonium hydroxide.  
   
   
       16 . The fuel composition of  claim 1 , wherein the liquid phase comprises dissolved therein one or more of LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Mg(OH) 2 , Ba(OH) 2 , Zn(OH) 2 , Al(OH) 3 , and NH 4 OH.  
   
   
       17 . The fuel composition of  claim 16 , wherein the liquid phase comprises dissolved therein at least one of NaOH and KOH.  
   
   
       18 . The fuel composition of  claim 1 , wherein the liquid phase comprises at least one of water, a (cyclo)aliphatic alcohol having up to about 6 carbon atoms and up to about 6 hydroxy groups, a C 2-4  alkylene glycol, a di(C 2-4  alkylene glycol), a poly(C 2-4  alkylene glycol), a mono-C 1-4 -alkyl ether of a C 2-4  alkylene glycol, di(C 2-4  alkylene glycol) or poly(C 2-4  alkylene glycol), a di-C 1-4 -alkyl ether of a C 2-4  alkylene glycol, di(C 2-4  alkylene glycol) or poly(C 2-4  alkylene glycol), an ethylene oxide/propylene oxide block copolymer, an ethoxylated aliphatic polyol, a propoxylated aliphatic polyol, an ethoxylated and propoxylated aliphatic polyol, an aliphatic ether having up to about 6 carbon atoms, an aliphatic ketone having up to about 6 carbon atoms, an aliphatic aldehyde having up to about 6 carbon atoms, a C 1-4 -alkyl ester of a C 1-4  alkanoic (aliphatic) acid and a primary, secondary or tertiary aliphatic amine having a total of up to about 10 carbon atoms.  
   
   
       19 . The fuel composition of  claim 18 , wherein the liquid phase comprises water and at least one of an aliphatic alcohol having up to about 6 carbon atoms and up to about 6 hydroxy groups, a C 2-4  alkylene glycol, a di(C 2-4  alkylene glycol), a poly(C 2-4  alkylene glycol), a mono-C 1-4 -alkyl ether of a C 2-4  alkylene glycol, a di(C 2-4  alkylene glycol) or a poly(C 2-4  alkylene glycol), a di-C 1-4 -alkyl ether of a C 2-4  alkylene glycol, a di(C 2-4  alkylene glycol) or a poly(C 2-4  alkylene glycol), an ethylene oxide/propylene oxide block copolymer, an ethoxylated and/or propoxylated aliphatic polyol, an aliphatic ether having up to about 6 carbon atoms, an aliphatic ketone having up to about 6 carbon atoms, and a primary, secondary or tertiary aliphatic amine having a total of up to about 10 carbon atoms.  
   
   
       20 . The fuel composition of  claim 1 , wherein the liquid phase comprises water and at least one 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.  
   
   
       21 . The fuel composition of  claim 1 , wherein the liquid phase comprises water.  
   
   
       22 . The fuel composition of  claim 21 , wherein the composition comprises two hydride compounds.  
   
   
       23 . A hydride containing fuel composition for a liquid fuel cell, wherein the composition comprises an alkaline liquid phase and at least a first hydride compound and a second hydride compound and wherein a solubility of the first hydride compound in the liquid phase is higher than a solubility of the second hydride compound in the liquid phase and a solubility of an anodic oxidation product of the first hydride compound in the liquid phase is lower than a solubility of an anodic oxidation product of the second hydride compound in the liquid phase, said alkaline liquid phase having a hydroxide ion concentration of at least about 0.5 mole per liter and comprising dissolved therein one or more of LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Mg(OH) 2 , Ba(OH) 2 , Zn(OH) 2 , Al(OH) 3  and NH 4 OH, and said first hydride compound and said second hydride compound being 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 , Al(BH 4 ) 3 , polyborohydrides, (CH 3 ) 3 NBH 3 , NaCNBH 3 , LiH, NaH, KH, CaH 2 , BeH 2 , MgH 2 , NaAlH 4 , LiAlH 4  and KAlH 4 .  
   
   
       24 . The fuel composition of  claim 23 , wherein at least one of the first hydride compound and the second hydride compound is selected from NaBH 4  and KBH 4 .  
   
   
       25 . The fuel composition of  claim 23 , wherein a molar ratio of the first hydride compound and the second hydride compound is from about 95:5 to about 5:95.  
   
   
       26 . The fuel composition of  claim 23 , wherein the composition comprises hydride compounds in a total concentration of at least about 1 mole per liter of composition.  
   
   
       27 . The fuel composition of  claim 26  wherein the hydroxide ion concentration is at least about 1 mole per liter of liquid phase.  
   
   
       28 . The fuel composition of  claim 23 , wherein the hydroxide ion concentration in the liquid phase is not higher than about 7 moles per liter of liquid phase.  
   
   
       29 . The fuel composition of  claim 27 , wherein the liquid phase comprises dissolved therein one or more of NaOH and KOH.  
   
   
       30 . The fuel composition of  claim 26 , wherein the liquid phase comprises water and at least one 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.  
   
   
       31 . A hydride containing fuel composition for a direct liquid fuel cell, wherein the composition comprises at least two different hydride compounds, the at least two different hydride compounds being such that the composition provides a higher efficiency than an otherwise identical fuel composition that comprises only one of the these different hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds.  
   
   
       32 . The composition of  claim 31 , wherein a first hydride compound of the at least two different hydride compounds has a higher solubility in a liquid phase of a liquid fuel than a second hydride compound of the at least two different hydride compounds and wherein an anodic oxidation product of the first hydride compound has a lower solubility in the liquid phase of the liquid fuel than an anodic oxidation product of the second hydride compound.  
   
   
       33 . A liquid fuel cell which comprises the fuel composition of  claim 1 .  
   
   
       34 . A liquid fuel cell which comprises the fuel composition of  claim 31 .  
   
   
       35 . A fuel cartridge for filling a liquid fuel cell, wherein the cartridge comprises the fuel composition of  claim 1 .  
   
   
       36 . A method of increasing the fuel efficiency of a hydride compound containing liquid fuel composition for a direct liquid fuel cell, wherein the method comprises employing at least two different hydride compounds in the fuel composition, the at least two different hydride compounds being selected such that a fuel composition comprising the at least two different hydride compounds 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.  
   
   
       37 . The method of  claim 36 , wherein a first hydride compound of the at least two different hydride compounds has a higher solubility in a liquid phase of the liquid fuel composition than a second hydride compound of the at least two different hydride compounds and wherein an anodic oxidation product of the first hydride compound has a lower solubility in the liquid phase of the liquid fuel composition than an anodic oxidation product of the second hydride compound.  
   
   
       38 . The method of  claim 37 , wherein the at least two hydride compounds are present in the liquid phase in a total concentration of at least about 1 mole per liter.  
   
   
       39 . The method of  claim 38 , wherein the at least two different hydride compounds comprise at least two borohydride compounds.  
   
   
       40 . A method of improving the performance of a liquid fuel cell which comprises a hydride compound containing liquid fuel composition, wherein the method comprises employing at least two different hydride compounds in the liquid fuel composition, the at least two different hydride compounds being selected such that 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 than, and shows at least the same efficiency as a liquid fuel composition which comprises only one of these hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds.