Water electrolyzers employing anion exchange membranes
Water electrolyzers employs base metal catalysts and an anion-conducting polymeric membrane with an area specific resistance at 60° C. in 1 M KOH below 0.037 ohm-cm 2 . Preferably, the membrane comprising a polymer of styrene, vinylbenzyl-R s and possibly vinylbenzyl-R x . R s is a positively charged cyclic amine group. R x is at least one constituent selected from the group consisting of —Cl, —OH, and a reaction product between an —OH or —Cl and a species other than a simple amine or a cyclic amine.
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 a cathode reactant introduced thereto via at least one cathode reactant flow channel;
(c) an anion exchange 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 said anion exchange membrane has an area specific resistance of about 0.045 ohm-cm 2 in 1 M KOH at 60° C.
2. The water electrolyzer of claim 1 , wherein said polymeric membrane has a thickness of from 10 to 300 micrometers.
3. The water electrolyzer of claim 1 , wherein said anion exchange membrane comprises a polymer comprising styrene and vinylbenzyl-R s , wherein R s is a positively charged cyclic amine group.
4. The water electrolyzer of claim 3 , wherein said polymer is a terpolymer of styrene, vinylbenzyl-R s , and vinylbenzyl-R x , wherein R x is at least one constituent selected from the group consisting of Cl, OH, and a reaction product between an OH or Cl and a species other than a simple amine or a cyclic amine, and wherein the total weight of the vinylbenzyl-R x groups is at least 0.3% of the total weight of the polymer electrolyte membrane.
5. The water electrolyzer of claim 3 , wherein the total weight of the vinylbenzyl-R s , groups in said polymer electrolyte membrane is between 15% and 90% of the total weight of the membrane.
6. The water electrolyzer of claim 3 , wherein the total weight of the vinylbenzyl-R x groups in said polymer electrolyte membrane is between 0.3% and 25% of the total weight of the membrane.
7. The water electrolyzer of claim 6 , wherein the total weight of the vinylbenzyl-R x groups in said polymer electrolyte membrane is between 1% and 15% of the total weight of the membrane.
8. The water electrolyzer of claim 3 , wherein said positively charged cyclic amine group is tetramethylimidazolium.
9. The water electrolyzer of claim 1 , wherein said anode catalyst comprises a base metal catalyst.
10. The water electrolyzer of claim 1 , wherein said cathode catalyst comprises a base metal catalyst.
11. The water electrolyzer of claim 1 , wherein said anode catalyst consists essentially of one or more base metal catalysts.
12. The water electrolyzer of claim 1 , wherein said cathode catalyst consists essentially of one or more base metal catalysts.
13. The water electrolyzer of claim 1 , wherein said cathode reactant comprises water.