Photoelectrochemical secondary cell and battery

Abstract

A photoelectrochemical secondary cell comprising a photocatalytic anode, or photoanode; an anode; a cathode comprising a metal hydride; electrolyte; separator; and case at least a portion of which is transparent to the electromagnetic radiation required by said photoanode to charge said photoelectrochemical secondary cell.

1 . A method of storing hydrogen by photochemically and/or electrochemically charging a metal hydride, the method comprising:
 a. providing a photoelectrochemical secondary cell comprising a photocatalytic anode or photoanode electrode, an anode electrode, a negative electrode comprising substantially a metal hydride, and an encased electrolyte capable of being reduced to hydrogen at the negative electrode, the photocatalytic anode or photoanode electrode, the anode electrode and the negative electrode, all being immersed in the electrolyte;   b. exposing the photocatalytic anode or photoanode electrode to radiation while applying zero bias voltage potential, or a bias voltage potential that is lower than the theoretical water splitting voltage of 1.48 VDC, between said photocatalytic anode or photoanode electrode and said negative electrode, and/or applying a voltage potential of at least 1.48 VDC between said anode electrode and said negative electrode, thereby charging said metal hydride with hydrogen.   
     
     
         2 . The method of  claim 1  wherein said applied potential is at least 2.0 volts of direct current. 
     
     
         3 . A method of storing hydrogen by photochemically and/or electrochemically charging a metal hydride, the method comprising:
 a. providing a photoelectrochemical secondary cell comprising a photocatalytic anode or photoanode electrode, an anode electrode, a negative electrode comprising substantially a metal hydride, and an encased electrolyte capable of being reduced to hydrogen at the negative electrode, the photocatalytic anode or photoanode electrode, the anode electrode and the negative electrode all being immersed in the electrolyte, and the photocatalytic anode or photoanode being electrically connected to the negative metal hydride electrode;   b. applying a direct current voltage potential between said anode electrode and said negative electrode, whereupon hydrogen is both produced and absorbed by the metal hydride of said negative electrode, thereby charging said metal hydride with hydrogen.   
     
     
         4 . The method of  claim 3  wherein said applied potential is at least 2.0 volts of direct current. 
     
     
         5 . An apparatus for photochemically and/or electrochemically storing hydrogen in a metal hydride, the apparatus comprising:
 a. a photoelectrochemical secondary cell comprising a photocatalytic anode or photoanode electrode, an anode electrode, a negative electrode comprising metal hydride affixed to an electrically conducting substrate, and an encased electrolyte capable of being reduced to hydrogen at the metal hydride negative electrode, said photocatalytic anode or photoanode being electrically connected to said metal hydride negative electrode, and said photocatalytic anode or photoanode electrode, said anode electrode and said negative electrode all being immersed in the electrolyte;   b. said photocatalytic anode or photoanode electrode and negative electrode further being electrically connected to the negative terminal of a direct current electrical power supply, and said anode electrode being electrically connected to the positive terminal of a direct current electrical power supply, and said anode electrode being electrically connected to the positive terminal of the direct current electrical power supply.   
     
     
         6 . The apparatus of  claim 5  wherein said photocatalytic anode or photoanode and negative electrode being electrically connected is achieved with a connecting busbar that is placed between the external terminal of the photoanode and of the negative electrode. 
     
     
         7 . The apparatus of  claim 5  wherein the case is provided with removable vents for filling electrolyte into said case. 
     
     
         8 . The apparatus of  claim 5  wherein said affixed metal hydride is removable from said conducting substrate and said apparatus. 
     
     
         9 . The apparatus of  claim 5  further comprising two titanium contacts and one stainless steel contact that protrude through the case and allow the photoanode, anode, and cathode respectively to be accessed electrically through the case in order to apply a bias voltage. 
     
     
         10 . The apparatus of  claim 5 . wherein said photocatalytic anode or photoanode electrode comprises one or more of the following: titania that is dyed; titania that is doped; strontium titanate; compounds and alloys of titania and titanium with tungsten, tungsten oxide, cadmium sulfide, iron, oxides of iron, or silicon; silicon seeded with nickel surface particles; nanotubes of titanium dioxide; carbon nanotubes further comprising semiconductor materials; graphene; quantum dots; photonic bandgap crystals; strained semiconductor; and strained titania. 
     
     
         11 . The apparatus of  claim 5  wherein said photocatalytic anode or photoanode electrode and said anode electrode are provided with apertures extending therethrough. 
     
     
         12 . The apparatus of  claim 4  wherein said anode electrode comprises at least one or more of: nickel hydroxide on nickel; mixed metal oxides of ruthenium, titanium and iridium on titanium; plated nickel or nickel hydroxide film on titanium; and nickel or nickel hydroxide particles on titanium; and wherein said titanium is a rod, plate, sheet, foil, or expanded mesh. 
     
     
         13 . The apparatus of  claim 5  wherein said anode electrode is formed by at least one or more of: applying a paste; sintering; calcification; thermal oxidation; anodizing; alloying; plating; powder coating; mechanical compression; casting; vacuum deposition; or chemical vapor deposition. 
     
     
         14 . The apparatus of  claim 5  wherein said gas separator comprises a non-woven felt of at least one or more of: polyolefin; polyethylene; or polypropylene. 
     
     
         15 . The apparatus of  claim 5  wherein said negative electrode comprises metal hydride in electrical contact with a nickel foam ribbon. 
     
     
         16 . The apparatus of  claim 5  wherein said metal hydride comprises a metal alloy of one or more of elemental forms: AB; AB2; AB5; or AB5-B. 
     
     
         17 . The apparatus of  claim 5  wherein said electrolyte comprises at least one of potassium hydroxide or potassium carbonate and may further comprise one or more of the following additives: co-electrolytes, additives for improved high or low temperature performance, or for viscosity or polymerization for leak containment, methanol; thickeners; co-electrolytes; or refractive index matching additives, or for more efficient gas evolution. 
     
     
         18 . The apparatus of  claim 5  wherein said case further comprises a portion or window that is transparent to electromagnetic radiation comprises at least one of ultraviolet-transmitting (UVT) acrylic or borosilicate 3.3 glass. 
     
     
         19 . The apparatus of  claim 5  wherein said case is constructed of an electrically conductive material such that said anode comprises a portion of said case. 
     
     
         20 . The apparatus of  claim 5  wherein said negative electrode is sealed to said case such that two compartments are formed within said case such that two different electrolytes can be retained within said case.