Gas diffusion composite electrode having polymeric binder coated carbon layer
AssigneeThe Dow Chemical Company
InventorCharles E. Goldsmith
Life of this patent
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Abstract
A gas diffusion composite electrode useful in an electrochemical cell comprising an electrochemically active layer and a backing layer, said active layer characterized as porous, homogeneous, hydrophilic, and electrolyte-permeable and comprising a sintered mixture of a major amount of an electrically conductive, hydrophilic, particulate material containing admixed therewith an electrochemically active catalyst, and a minor amount of a hydrophobic polymer, said particulate material being substantially coated with said hydrophobic polymer by precipitation of said hydrophobic polymer upon said particulate material.
Claims23
A gas diffusion composite electrode useful in an electrochemical cell, comprising an electrochemically active layer and a backing layer, said active layer characterized as porous, homogeneous, hydrophilic, and electrolyte-permeable and comprising a sintered mixture of a major amount of an electrically conductive, hydrophilic, particulate material containing admixed therewith an electrochemically active catalyst, and a minor amount of a hydrophobic polymer, said particulate material being substantially coated with said hydrophobic polymer by precipitation of said hydrophobic polymer upon said particulate material.
A method for the preparation of a gas diffusion composite electrode comprising an electrolyte-permeable, homogeneous polymer active layer, a backing layer, and a current distributor comprising the steps of:
- (A) preparing an electrochemically active material dispersion consisting essentially of a liquid dispersion medium, a hydrophobic polymer and a major amount of an electrically conductive, hydrophilic, particulate material containing admixed therewith an electrochemically active catalyst;
- (B) precipitating said hydrophobic polymer upon said particulate material from aid dispersion and removing enough of said dispersion medium to obtain a dry precipitate;
- (C) drying the precipitate obtained to remove substantially all of said dispersion medium;
- (D) mixing the dried precipitate with a liquid dispersion medium to produce a cohesive and pliable dough;
- (E) subjecting the dough to a fibrillation step in which the dough is shear-blended and thereafter calendering said dough to form an electrolyte-permeable polymer layer;
- (F) laminating said electrolyte-permeable polymer layer to a current distributor and a backing layer comprising a hydrophobic polymer and a pore-forming material;
- (G) sintering said layers;
- and
- (H) removing said pore-forming material.
An electrochemically active layer of a composite gas diffusion electrode useful as an electrode in an electrochemical cell, said layer characterized as porous, homogeneous, hydrophilic, and electrolyte-permeable comprising a sintered mixture of a major amount of an electrically conductive, hydrophilic, particulate material containing admixed therewith an electrochemically active catalyst and substantially coated with a minor amount of a hydrophobic polymer precipitated upon said particulate mateial.
A method for the preparation of an electrolyte-permeable, homogeneous polymer sheet useful as the electrochemically active layer of a composite gas diffusion electrode useful in an electrochemical cell, comprising the steps of:
- (A) preparing an electrochemically active material dispersion consisting essentially of a liquid dispersion medium, a hydrophobic polymer and a major amount of an electrically conductive, hydrophilic, particulate material containing admixed therewith an electrochemically active catalyst;
- (B) precipitating said hydrophobic polymer upon said particulate material and removing enough of said dispersion medium to obtain a dry precipitate;
- (C) drying the precipitate obtained to remove substantially all of said dispersion medium;
- (D) mixing the precipitate obtained in (B) with a liquid dispersion medium to produce a cohesive and pliable dough;
- (E) subjecting the dought to a fibrillation step in which the dough is shear-blended and thereafter calendering said dough to form said electrolyte-permeable polymer sheet;
- and
- (F) sintering said polymer sheet.
Dependencies are inferred from the claim text.