Electrode for electrochemical reduction of oxygen and process for its production

Claim 2

An electrode as claimed in claim 1, wherein said catalyst material has a carbon content of up to 10 percent by weight.

Claim 3

An electrode as claimed in claim 1, wherein the porous electrode body is provided on its gas side with at least one hydrophobic layer.

Claim 4

An electrode as claimed in claim 4, wherein the hydrophobic layer consists of polytetrafluoroethylene.

Claim 5

An electrode as claimed in claim 1, wherein the porous electrode body is a sintered body.

Claim 6

An electrode as claimed in claim 1, wherein an electronically conductive support structure is arranged at least partially within the porous electrode body.

Claim 7

A process for the production of oxygen electrodes comprising a porous sintered electrode body containing a catalyst for the electrochemical reduction of oxygen in an alkaline electrolyte, said process comprising the steps of: preparing a powder mixture comprising at most 10 percent by weight of active carbon and at least two metals selected from the group consisting of nickel, cobalt, iron and manganese, the amount of carbon in said mixture being chosen so as to allow formation of a non-stoichiometric mixed carbide of at least said two metals; forming a liquid suspension of said powder mixture and spraying said suspension onto a metallic support structure so as to deposit thereon a given amount of said mixture; forming said sintered electrode body by subjecting the mixture deposited on said support to sintering under vacuum or an inert gas atmosphere, with subsequent cooling, so as to produce a topochemical reaction between the particles of the deposited powder mixture and to transform said mixture into said catalyst in the form of a non-stoichiometric mixed carbide of at least two of said metals, said carbide forming a major part of said sintered electrode body.

Claim 8

The process of claim 8 comprising the step of tempering said catalyst after said sintering step in a protective atmosphere at a temperature within the upper region of existence of the mixed carbide.

Claim 9

The process of claim 9, comprising the steps of applying a porous hydrophobic layer by spraying on to the gas side of said electrode body, applying under pressure a porous hydrophobic membrane to said layer and heating in such manner as to simultaneously provide sintering of said layer and membrane to said electrode body and said tempering of the catalyst.

Claim 10

The process of claim 8, wherein the powder mixture has a composition in parts by weight of from about 45 percent to about 75 percent of nickel, about 20 to 50 percent of cobalt and about 5 to 10 percent of active carbon.

Claim 11

The process of claim 8, wherein the powder mixture has a composition in parts by weight of about 75 percent of nickel, 19 percent of manganese and 6 percent of active carbon.