Water Electrolyzers Employing Anion Exchange Membranes
Water electrolyzers comprises an anode comprising a quantity of anode catalyst, a cathode comprising a quantity of cathode catalyst with an inlet for introducing a cathode reactant thereto, an anion-conducting polymer electrolyte membrane interposed between said anode and said cathode, and a source of electrical energy that applies a voltage between the anode and cathode. At least one of said anode catalyst or said cathode catalyst comprises a metal or metal alloy having a surface area of at least 12 m 2 /gm. Water electrolyzers preferably employ base metal catalysts and an anion-conducting polymeric membrane with a resistance below 0.3 ohm-cm 2 and a base metal catalyst with a surface area of at least 12 m 2 /mg.
1 . A water electrolyzer comprising:
(a) an anode comprising a quantity of anode catalyst;
(b) a cathode comprising a quantity of cathode catalyst, said cathode having an inlet for introducing a cathode reactant thereto;
(c) an anion-conducting polymer electrolyte membrane interposed between said anode and said cathode; and
(d) a source of electrical energy that applies a voltage between the anode and cathode,
wherein at least one of said anode catalyst or said cathode catalyst comprises a metal or metal alloy having a surface area of at least 12 m 2 /gm.
2 . The water electrolyzer of claim 1 , wherein said cathode catalyst comprises a base metal.
3 . The water electrolyzer of claim 2 , wherein said cathode catalyst comprises a metal or metal alloy with a surface area of at least 20 m 2 /gm.
4 . The water electrolyzer of claim 3 , wherein said cathode catalyst comprises a metal or metal alloy with a surface area of at least 30 m 2 /gm.
5 . The water electrolyzer of claim 4 , wherein said cathode catalyst comprises a metal or metal alloy with a surface area of at least 50 m 2 /gm.
6 . The water electrolyzer of claim 2 , wherein said cathode catalyst comprises nickel or a nickel alloy.
7 . The water electrolyzer of claim 2 , wherein said cathode catalyst comprises a porous metal.
8 . The water electrolyzer of claim 7 , wherein said cathode catalyst comprises a spongy metal.
9 . The water electrolyzer of claim 8 , wherein said cathode catalyst comprises at least one of nickel sponge or Raney nickel.
10 . The water electrolyzer of claim 2 , wherein said anion-conducting polymer electrolyte membrane has a resistance below 1 ohm-cm 2 in 1 M KOH at 60° C.
11 . The water electrolyzer of claim 10 , wherein said anion-conducting polymer electrolyte membrane has a resistance below 0.3 ohm-cm 2 in 1 M KOH at 60° C.
13 . The water electrolyzer of claim 10 , wherein said anion-conducting polymer electrolyte membrane has a resistance below 0.1 ohm-cm 2 in 1 M KOH at 60° C.
14 . The water electrolyzer of claim 3 , wherein said cathode catalyst comprises a catalyst layer on at least one of:
(a) said an anion-conducting polymer electrolyte membrane;
(b) a gas diffusion layer;
(c) a metal fiber paper; and
(d) a metal grid or screen.
15 . The water electrolyzer of claim 14 , wherein said catalyst layer is no more than 80 nm thick.
16 . The water electrolyzer of claim 15 , wherein said catalyst layer is no more than 60 nm thick.
17 . The water electrolyzer of claim 15 , wherein said catalyst layer has a thickness of 15-20 nm.
18 . The water electrolyzer of claim 1 , wherein said cathode reactant comprises water.