Inks for nanofiber fuel cell electrode and membrane-electrode-assemblies, and methods of ink formulations
An ink for forming nanofiber fuel cell electrodes, and methods of ink formulations, and membrane-electrode-assemblies for electrochemical devices. The ink includes a first amount of a catalyst, a second amount of an ionomer in a salt form, and a third amount of a carrier polymer dispersed in one or more solvents, where a weight ratio of the first amount to the second and third amounts is in a range of about 1-1.5, and a weight ratio of the second amount to the third amount is in a range of about 1-3. The ink has a solids concentration in a range of about 1-30 wt %. Preferably, the solids concentration is in a range of about 10-15%.
1. An ink usable for forming a fiber electrode for an electrochemical device, comprising:
a catalyst, an ionomer in a salt form, and a carrier polymer dispersed in one or more solvents, wherein the salt form of the ionomer has some or all of ion-exchange sites in a form SO 3 X, wherein X is a monovalent metal cation, a quaternary ammonium cation, or a multivalent cation, wherein the monovalent metal cation comprises Na + , Li + or Cs + , the quaternary ammonium cation comprises N(CH 3 ) 4 + or N(CH 2 CH 3 ) 4 + and the multivalent cation comprises Ni 2+ or Co 2+ ,
wherein the catalyst comprises Pt/C;
wherein the ionomer comprises a perfluorosulfonic acid (PFSA) polymer including Nafion®,
wherein the carrier polymer comprises polyethylene oxide (PEO), and wherein PEO is about 1 wt % of a total weight of the ink; and
wherein a weight ratio of Pt/C:salt-form Nafion®:PEO is 52:37:11.
2. The ink of claim 1 , wherein the one or more solvents comprise water and isopropyl alcohol (IPA) with a solvent weigh ratio being 1:1 water:IPA, or water, methanol and n-propanol with a solvent weigh ratio being 2:1:1 water:methanol:n-propanol.
3. A membrane-electrode-assembly (MEA) for an electrochemical device, comprising:
an anode, a cathode and a membrane disposed between the anode and the cathode,
wherein at least one of the cathode and the anode is formed of a fiber electrode comprising a network of fibers formed by spinning an ink containing a catalyst, an ionomer in a salt form, and a carrier polymer dispersed in one or more solvents, wherein the salt form of the ionomer has some or all of ion-exchange sites in a form SO 3 X, wherein X is a monovalent metal cation, a quaternary ammonium cation, or a multivalent cation, wherein the monovalent metal cation comprises Na + , Li + , or Cs + , the quaternary ammonium cation comprises N(CH 3 ) 4 + or N(CH 2 CH 3 ) 4 + and the multivalent cation comprises Ni 2+ , or Co 2+ ,
wherein the catalyst comprises Pt/C;
wherein the ionomer comprises a perfluorosulfonic acid (PFSA) polymer including Nafion®;
wherein the carrier polymer comprises polyethylene oxide (PEO), and wherein PEO is about 1 wt % of a total weight of the ink; and
wherein a weight ratio of Pt/C:salt-form Nafion®:PEO is 52:37:11.
4. Fibers being formed by spinning an ink, the ink comprising:
a catalyst, an ionomer in a salt form, and a carrier polymer dispersed in one or more solvents, wherein the salt form of the ionomer has some or all of ion-exchange sites in a form SO 3 X, wherein X is a monovalent metal cation, a quaternary ammonium cation, or a multivalent cation, wherein the monovalent metal cation comprises Na + , Li + or Cs + , the quaternary ammonium cation comprises N(CH 3 ) 4 + or N(CH 2 CH 3 ) 4 + and the multivalent cation comprises Ni 2+ or Co 2+ ,
wherein the catalyst comprises Pt/C;
wherein the ionomer comprises a perfluorosulfonic acid (PFSA) polymer including Nafion®;
wherein the carrier polymer comprises polyethylene oxide (PEO), and wherein PEO is about 1 wt % of a total weight of the ink; and
wherein a weight ratio of Pt/C:salt-form Nafion®:PEO is 52:37:11.
5. The fibers of claim 4 , wherein the solids concentration is in a range of about 10-15% wt % of the total weight of the ink.
6. The fibers of claim 4 , wherein the one or more solvents comprise water and isopropyl alcohol (IPA) with a solvent weigh ratio being 1:1 water:IPA, or water, methanol and n-propanol with a solvent weigh ratio being 2:1:1 water:methanol:n-propanol.
7. The fibers of claim 4 , wherein the PFSA polymer comprises Nafion®, Aquivion®, Aciplex™, some other low equivalent weight PFSA, or a polymer containing F atoms and cation-exchange sites.