Method of producing a metal borohydride or boric acid from metal metaborate

A method of producing metal borohydride, M(BH4)n, from metal metaborate, M(BO2)n, or one of its hydrates, M(BO2)n·xH2O, as a starting material, in which M is a metal, such as a metallic metal, an alkali metal, an alkaline earth metal, a transition metal or a chemical compound behaving as a metal, n is a valence value of the metal, and x is a number of water molecules associated with the metal metaborate in a respective hydrate, metal borohydride is formed through a reaction of metal hydride, MHn, with trimethyl borate, B(OMe)3, and trimethyl borate is formed through a reaction of boric acid, H3BO3, with methanol, MeOH, under removal of water, H2O,

• wherein an electrochemical cell (100) is used for the conversion of metal metaborate and water, H2O, to boric acid, in the electrochemical cell according to, at least substantially, an overall reaction according to the reaction formula
• 4M(BO2)n+10nH2O→4nH3BO3+4M(OH)n+nO2+2nH2,
• wherein the electrochemical cell has an anodic half-cell (110) with an anode (115) and, at least substantially, water as a liquid in the anodic half-cell, a cathodic half-cell (120) with a cathode (125) and, at least substantially, water as a liquid in the cathodic half-cell, and a cation exchange membrane separating the anodic half-cell and the cathodic half-cell,
• wherein a positive pole and a negative pole of an electric potential source are connected to the anode and the cathode, respectively,
• wherein, at least substantially, metal metaborate is provided to the water in the anodic half-cell to provide a solution of metal metaborate in water in the anodic half-cell, and, in the anodic half-cell, acid ions, H+, and electrons, e−, are generated at the anode from electrolysis of water for H+ to react with metal metaborate and water, according to the reaction formulas
• 2nH2O→4nH++nO2+4n e−, and
• 4M(BO2)n+4nH++4nH2O→4nH3BO3+4Mn+,
• to have, at least substantially, an overall reaction in the anodic half-cell according to the reaction formula
• 4M(BO2)n+6nH2O→4nH3BO3+nO2+4Mn++4n e−,
• wherein the cation exchange membrane passes metal ions, Mn+, from the anodic half-cell to the cathodic half-cell, and
• wherein, in the cathodic half-cell, hydroxide ions, OH−, are generated at the cathode from water and electrons, e−, from the cathode, to form metal hydroxide, M(OH)n, from metal ions and water, according to the reaction formulas
• 4nH2O+4n e−→2nH2+4nOH−, and
• 4Mn++4nOH−→4M(OH)n,
• to have, at least substantially, an overall reaction in the cathodic half-cell according to the reaction formula
• 4Mn++4nH2O+4n e−→4M(OH)n+2nH2.