Gas diffusion substrate

Patent metadata

Field	Value
Publication number	US-10424795-B2
Application number	US-201515116572-A
Country	US
Kind code	B2
Filing date	Feb 4, 2015
Priority date	Feb 5, 2014
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

A porous gas diffusion substrate that includes: (a) a porous non-woven web comprising carbon fibers; and (b) a carbonaceous residue; wherein the carbonaceous residue is embedded within the porous non-woven web; (c) a fluorinated polymer; and (d) inert particles wherein at least some of the carbon fibers of the porous non-woven web have a coating comprising the fluorinated polymer and inert particles is disclosed.

First claim

The invention claimed is:

1. A porous gas diffusion substrate comprising:
(a) a porous non-woven web comprising individual carbon fibres; and
(b) a carbonaceous residue; wherein the carbonaceous residue is embedded within the porous non-woven web;
(c) a fluorinated polymer; and
(d) inert particles wherein the inert particles comprise particulate graphite, particulate carbon, carbon black, metal oxide, refractory oxide, or metal carbide;
wherein the fluorinated polymer is present at a concentration of 1-20 weight % with respect to the weight of the porous gas diffusion substrate without the coating;
wherein at least some of the carbon fibres of the porous non-woven web have a coating on the individual fibers comprising the fluorinated polymer and inert particles; and
wherein the inert particles of the coating are present at a concentration of 0.1-10 weight % of the weight of the fluorinated polymer.

2. The porous gas diffusion substrate according to claim 1 , wherein the fluorinated polymer is selected from the group consisting of: fluorinated ethylene propylene (FEP); polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF) polytetrafluoroethylene (PTFE); polychlorotrifluoroethylene (PCTFE); perfluoroalkoxy polymer (PFA); polyethylenetetrafluoroethylene (ETFE); polyethylenechlorotrifluoroethylene (ECTFE); perfluorinated elastomer [perfluoroelastomer] (FFPM/FFKM); fluorocarbon [chlorotrifluoroethylenevinylidene fluoride] (FPM/FKM); perfluoropolyether (PFPE); perfluorosulphonic acid (PFSA); and perfluoropolyoxetane.

3. The porous gas diffusion substrate according to claim 1 , wherein the inert particles are particulate graphite or particulate carbon.

4. The porous gas diffusion substrate according to claim 1 , wherein the inert particles have a largest dimension of from 0.1 to 20 microns.

5. The porous gas diffusion substrate according to claim 1 , wherein at least 50% of the carbon fibres have a coating comprising the fluorinated polymer and inert particles.

6. The porous gas diffusion substrate according to claim 1 , wherein the coating on the carbon fibres is complete.

7. The porous gas diffusion substrate according to claim 1 , wherein the coating on the carbon fibres is incomplete.

8. The porous gas diffusion substrate according to claim 1 , wherein the gas diffusion substrate further comprises electrically conductive carbonaceous particles embedded within the porous non-woven web.

9. A process for the manufacture of the porous gas diffusion substrate according to claim 1 , the process comprising the steps:
(i) providing a porous non-woven web comprising carbon fibres;
(ii) providing a dispersion comprising a carbonisable resin;
(iii) impregnating the porous non-woven web with the dispersion prepared in step (ii);
(iv) carrying out a curing step to cure the carbonisable resin at a temperature of from 100° C. to 300° C.;
(v) carrying out a heat treatment step to carbonise/graphitise the carbonisable resin at a temperature of from 900° C. to 3000° C. to provide a gas diffusion substrate precursor;
(vi) providing a dispersion comprising water, fluorinated polymer and inert particles;
(vii) treating the gas diffusion substrate precursor with the dispersion prepared in step (vi);
(viii) drying; and
(ix) heating at a temperature of up to 400° C. to provide the gas diffusion substrate.

10. A gas diffusion layer comprising a porous gas diffusion substrate as claimed in claim 1 and a microporous layer applied to one face of the porous gas diffusion substrate.

11. A gas diffusion electrode comprising a gas diffusion substrate as claimed in claim 1 and an electrocatalyst layer present on one face of the porous gas diffusion substrate.

12. A gas diffusion electrode comprising a gas diffusion layer as claimed in claim 10 and an electrocatalyst layer present on the face of the gas diffusion layer having the microporous layer.

13. A membrane electrode assembly comprising a porous gas diffusion substrate as claimed in claim 1 , a polymer electrolyte membrane and an electrocatalyst layer between the porous gas diffusion substrate and the polymer electrolyte membrane.

Assignees

• Johnson Matthey Fuel Cells Ltd
• Technical Fibre Products Ltd

Inventors

• Cash James Matthew
• Jeschke Michael
• Wright Victoria Jane
• Sharman Jonathan David Brereton

Classifications

• H01M8/0234 Primary

  Carbonaceous material · CPC title

• H01M4/8605

  Porous electrodes · CPC title

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title

• H01M8/0245

  in the form of layered or coated products · CPC title

• H01M4/8807

  Gas diffusion layers · CPC title