GB1153337A - Carbon Electrodes. - Google Patents

Abstract

1,153,337. Carbon electrodes. DEUTSCHE AKADEMIE DER WISSENSCHAFTEN ZU BERLIN. 6 Sept., 1966, No. 39777/66. Heading H1B. A carbon electrode for galvanic elements consists of a hydrophobic carbon body provided with a hydrophilic covering layer, the carbon body consisting of activated carbon, optionally in admixture with graphite, and a hydrophobic binding agent and the covering layer consisting of activated carbon, optionally in admixture with graphite, a catalyst which increases the electrochemical loading capacity of the finished electrode and/or promotes the thermal decomposition of the binder and a hydrophobic binding agent and decomposition products thereof, the amount of binding agent in the covering layer being less than the amount of binding agent in the carbon body. As current lead-off and for increasing the mechanical stability, a metal mesh or cross-piece is provided within the covering layer or in the immediate vicinity thereof within the hydrophobic part of the carbon body. The covering layer may also contain a wetting agent for the improvement of the hydrophilic properties thereof. The electrodes may be prepared by the partial decomposition of the binding and hydrophobing agent with the simultaneous separation of catalyst. This may be achieved by forming a pressed body of activated or unactivated carbon powder and a hydrophobic binding agent at 20‹ to 400‹ C., superficially impregnating or spraying the pressed body with a solution of a salt of a catalyst and heating to separate the catalyst and for the decomposition of the binding agent. The binding and hydrophobing agent may be natural rubber, polytetrafluoroethylene, polystyrene, polyethylene, a fluorine-carbon copolymer or polyethylene wax. In a typical example, tempered activated carbon and an aqueous dispersion of polytetrafluoroethylene are mixed, dried and together with a lead-off are coldpressed to form a carbon body, which is partially immersed in a silver nitrate solution and then heated at 390‹ C. to separate out the catalyst and to provide a hydrophilic covering layer.