| 摘要 |
1,221,543. Porous gas electrodes. GENERAL ELECTRIC CO. 28 June, 1968 [30 June, 1967], No. 31057/68. Heading H1B. Gas electrodes comprise a fluid-permeable electrocatalytically active mass having an internal pore network having the same geometric configuration as the solid material of an open cellular foam, and a current collector in electrical contact therewith. The electrodes are formed by contacting an open cellular foam with a more noble current collector, filling at least the voids of the foam with the active mass and removing the material of the foam. The active mass may also contain particles of a leachable substance to produce secondary pores, and a layer of a gas-permeable hydrophobic polymer may be applied to one surface of the electrode. The current collector may be a screen, expanded metal, foam or felt of Ti, Ta, Pt, An or Ag or their alloys. The open foam may be of metal, e.g. Ni, Fe, Co, Zn, Cu, Ag, Al, Mg or their alloys, and be removed by leaching with an acid, e.g. HNO 3 , or it may be of an organic polymer which may be removed chemically or by burning out or vaporization, e.g. during the sintering of the active mass. The active mass preferably comprises a perfluorinated polymer binder and an electrocatalyst, e.g. Pt or a spinal with or without an additional electrical conductor, e.g. C or B 4 C, whilst the leachable particles therein may be of e.g. calcim metasilicate or SiO 2 . The active mass is applied to the foam in the form of a paste. Examples describe making of electrodes by pressing a Pt-screen into an Ni-foam, pasting the composite with a Pt-PTFE composition optionally containing particles of SiO 2 or calcium metasilicate, leaching the foam with HNO 3 , the SiO 2 with aq. NaOH, and the metasilicate in an aq. HNO 3 + HF and optionally applying a PTFE film to one surface. In another example the foam of an Ni-foam, Ptscreen composite is platinized and the composite is pasted with an aq. mixture of B 4 C 3 and PTFE. After drying and sintering the Ni-foam is leached out with aq. HNO 3 and a PTFE film is sprayed on to the surface of the leached foam side. The electrodes can be used in fuel cells with aqueous or ion-exchange membrane electrolytes as either anode or cathode and as cathodes in metal-air cells. |
