Preparation of double-layer electrodes

Abstract

Abstract 1,141,814. Fuel cell electrodes. ROBERT BOSCH G.m.b.H. 6 July, 1966 [20 July, 1965], No. 30351/66. Heading H1B. Fuel cell electrodes comprising 2 bonded microporous layers of sintered nickel and silver particles are made by (a) forming a layer of finely divided nickel and finely divided silver carbonate, (b) forming another layer of finely divided nickel, finely divided silver carbonate and a removable pore-forming material in contact with it, (c) compressing the 2 layers, (d) sintering them and reducing the silver carbonate to metallic silver and (e) removing the pore forming material. The silver carbonate may be reduced with H 2 or by thermal decomposition in an inert gas stream. The first layer may be prepared from 40-80% silver carbonate and 60-20% nickel. The pore former may be a volatile material, e.g. ammonium carbonate, ammonium bicarbonate or ammonium carbamate, or a soluble material, e.g. Na 2 CO 3 , NaHCO 3 or MgCO 3 which is dissolved out after sintering. They may be of less than 100 mÁ grain size and 17-83% may be used. The layers 1-3 mm. thick, may be subjected to a pressure of 1-3 Kg/cm.<SP>2</SP> It may be sintered at 550-650‹ C. whilst being pressed flat. Reduced pressure may be used to remove volatile pore formers. The electrode may be used with air in a methanol cell at room temperature or in a hydrogen cell at room or elevated temperature. In a particular embodiment it (a) is retained by frame (c) in proximity to plate (e), the cavity between being sealed by ring (d). Current is collected by (f) and gas supplied at (g) and removed at (h). The electrode is immersed in 7N.KOH solution opposite a hydrogen electrode and air preheated to 70‹ C. is passed through at such a rate that no bubbles escape through the electrolyte. The air pressure may be 0À4-0À8 atmospheres gauge. In a modification of the invention the silver in layer (a) is replaced by nickel derived by heating basic nickel carbonate.

Inventors

• 👤 Sandstede Gerd
• 👤 Binder Horst
• 👤 Kohling Alfons

Bibliographic Details