Nanofiber-based bipolar membranes, fabricating methods and applications of same

1. A bipolar membrane, comprising:

an internal 3-dimensional (3D) bipolar interface; and

a first layer, a second layer, and a third layer,

wherein the first layer comprises a cation exchange dense layer formed of one or more cation exchange polymers;

wherein the third layer comprises an anion exchange dense layer formed of one or more anion exchange polymers; and

wherein the second layer, disposed between the first layer and the third layer, comprises a mixture of at least one cation exchange polymer and at least one anion exchange polymer, such that an interface of the at least one cation exchange polymer and the at least one anion exchange polymer construes the internal 3D bipolar interface that has a large area, and wherein the at least one cation exchange polymer in the second layer is connected to the one or more cation exchange polymers of the first layer, and the at least one anion exchange polymer in the second layer is connected to the one or more anion exchange polymers of the third layer.

2. The bipolar membrane of claim 1 , wherein the at least one cation exchange polymer in the second layer is same as or different from the one or more cation exchange polymers of the first layer, and the at least one anion exchange polymer in the second layer is same as or different from the one or more anion exchange polymers of the third layer.

3. The bipolar membrane of claim 1 , wherein the internal 3D bipolar interface comprises a mixture of cation exchange and anion exchange nanofibers.

4. The bipolar membrane of claim 1 , wherein the one or more cation exchange polymers of the first layer comprise at least one of polymers containing protogenic groups including sulfonic, sulfonimide, phosphonic and carboxylic, and their derivatives.

5. The bipolar membrane of claim 4 , wherein the one or more cation exchange polymers of the first layer comprise at least one of poly(arylene ether sulfonic acid), poly(phenylsulfone sulfonic acid), poly(phenylene oxide sulfonic acid), poly(arylene sulfonic acid), poly(phosphazene sulfonic acid), sulfonated polybenzimidazole, perfluorosulfonic acid polymers, poly(vinylphosphonic acid), poly(acrylic acid), poly(methacrylic acid) and their copolymers, carboxyphenoxymethylpolysulfone, and their derivatives.

6. The bipolar membrane of claim 5 , wherein the perfluorosulfonic acid polymers compress Nafion®, Aquivion®, or their derivatives.

7. The bipolar membrane of claim 4 , wherein the one or more cation exchange polymers of the first layer comprise sulfonated poly(ether ether ketone) (SPEEK).

8. The bipolar membrane of claim 1 , wherein the one or more anion exchange polymers of the third layer comprise at least one of polymers containing positive fixed charge groups including quaternary ammonium, guanidinium, phosphonium, and their derivatives.

9. The bipolar membrane of claim 8 , wherein the one or more anion exchange polymers of the third layer comprise at least one of polymers based on polyarylene or on aliphatic hydrocarbon backbone.

10. The bipolar membrane of claim 8 , wherein the one or more anion exchange polymers of the third layer comprises quaternized poly(phenylene oxide) (QPPO).

11. The bipolar membrane of claim 1 , wherein the first layer comprises a mixture of two or more cation exchange polymers, and wherein the third layer comprises a mixture of two or more anion exchange polymers.

12. The bipolar membrane of claim 1 , wherein each of the first layer and the third layer comprises uncharged particles for improving mechanical strength and/or increasing ionic conductivity, wherein the uncharged particles comprises graphene, graphene oxide, carbon nanotubes, short polymer fibers, and sulfonated or aminated polyhedral oligomeric silsesquioxane (POSS) nanoparticles.

13. The bipolar membrane of claim 1 , wherein a polymer blend of an anion exchange ionomer with one or more charged or uncharged polymers is employed in any of the first, second and third layers.

14. The bipolar membrane of claim 1 , wherein a polymer blend of a cation exchange ionomer with one or more charged or uncharged polymers is employed in the first, second and third layers.

15. The bipolar membrane of claim 1 , wherein at least one of the first, second and third layers is further reinforced with polymer fibers being made of an ion-exchange or uncharged polymer including poly(phenyl sulfone) or poly(phenylene oxide), poly(vinylidene fluoride).

16. The bipolar membrane of claim 1 , wherein the 3D bipolar interface comprises catalyst particles.

17. The bipolar membrane of claim 16 , wherein the catalyst particles comprise inorganic and organic particles, or polymers.

18. The bipolar membrane of claim 17 , wherein the catalyst particles comprise poly(vinyl pyridine), poly(ethylene imine), poly(vinyl alcohol), poly(acrylic acid), silica, functionalized silica, Al(OH) 3 , Fe(OH) 3 , Fe 2 O 3 , Ca(OH) 2 , Mg(OH) 2 , FeCl 3 , RuCl 3 , Cr(NO 3 ) 3 , ZrO 2 , sodium metasilicate, graphene oxide and polymers or particles with phosphoric or phosphonic acid groups.

19. The bipolar membrane of claim 1 , wherein the internal 3D bipolar interface is a junction layer of interpenetrating polymer nanofibers or microfibers of anion-exchange polymer and cation-exchange polymer, with or without catalyst particles.

20. The bipolar membrane of claim 1 , wherein the internal 3D bipolar interface is a junction layer of polymer nanofibers or microfibers of anion-exchange polymer or cation-exchange polymer embedded in a matrix of cation-exchange or anion-exchange polymers, respectively, with or without catalyst particles.

21. The bipolar membrane of claim 19 , wherein the interpenetrating polymer fiber junction layer has no void space between the fibers.

22. The bipolar membrane of claim 19 , wherein there is some void space between the interpenetrating polymer fibers in the junction layer.

23. A fuel cell, comprising at least one bipolar membrane according to claim 1 .

24. An electrochemical device, comprising at least one bipolar membrane according to claim 1 .