Patent GB-1137127-A (GB)
Title: Electrodes particularly useful for fuel cells
Inventor: DUC JOSEPH ADRIEN MAHER LE
IPC: H01M4/88
Filed: 1965-12-20
Abstract: 1,137,127. Fuel cell electrodes. PULLMAN Inc. 20 Dec., 1965 No. 53964/65. Heading H1B. [Also in Division C7] A fluid diffusion electrode suitable for use in batteries or fuel cells is produced by successively (a) contacting a non-metallic porous solid with a reducing agent, (2) contacting the so-treated solid with a solution of a readilyreducible compound of a metal to deposit the metal on the surface of the solid, (3) depositing a conductive metal on the metallized surface by electroless plating, and (4) electroplating a continuous layer of conductive metal on and within the pores of the non-metallic solid. The non-metallic body may be a sheet of thermoplastic or natural or synthetic elastomers such as alkylene or vinyl polymers which may be halogenated and may be co-polymerized with phenol- or urea-formaldehyde resins or casein; synthetic ion-exchange resins; ceramics, metal oxide refractories, porous glass, porous graphite, or asbestos; woven textiles or woven asbestos, glass or other inorganic fibres; mats of deposited fibres, asbestos paper, parchments; or PTFE- coated woven glass fibres, or woven graphite formed by pyrolysis of woven synthetic fibre. The non-metallic body may be a sheet or a series of contiguous tubes formed by bonding two corrugated plastic or elastomeric sheets along their registered ridges. The chemical plating steps (1) to (3) may be assisted by passing the treating solutions through the porous body by a vacuum impregnating technique. The metals used for the conductive layers may be any selected from Periodic Groups I, IIB, III to VIII, and may include alloys. Typically the reducing agent of step (1) is stannous chloride or hydrazine applied in aqueous solution and the reacting metal solution of step (2) contains PdCl 2 , KAu(CN) 2 , or H 2 PtCl 6 . The electroless plating solution may contain CuSO 4 , Cu(NO 3 ) 2 , NiCl 2  and/or CoCl 2 , KAu(CN) 2 , FeSO 4 , or Pd(NH 3 ) 4 Cl 2  together with a reducing agent such as formaldehyde, hydrazine or NaH 2 PO 2 , a complexing agent such as sodium citrate, sodium EDTA or Rochelle salt, and optionally NH 4 Cl. Typically the electroplated metal is Ag from a cyanide bath but reference is made to electroplating with Au, Zn, Al, Mn, Fe, Pt, Pd. The resulting electrodes may have a resistivity between 5 and 10 times that of a porous conductor of the same metal, e.g. silver; and may be impregnated with catalyst metal or oxides or salts of such metals either simultaneously with the conductive metal or subsequently by electroless or electrolytic plating, vapour deposition, sputtering, electrophoretic deposition or by impregnation with catalyst precursors followed by decomposition, or by anodizing the electrode surface with or without pre-treatment with reducible salts. The electrodes may be used in a fuel cell either as the fuel electrode fed with hydrogen, hydrocarbons, or alcohols or as the oxidizing electrode fed with air, oxygen, chlorine or bromine, using as electrolyte aqueous or non- aqueous solutions, molten inorganic salts or liquefied gases e.g. NH 3 . The electrodes may also be employed as one or both of two electrodes sandwiching a porous layer impregnated with a catalyst with optionally a metal screen or perforated plate between the catalyst layer and the electrodes. Silver-zinc and silver-nickel batteries may include porous electrodes formed as described above.