NOVELTY - Gas electrode comprises multiple layers (2, 3, 4) allowing the passage of reactive species through the electrode layers stacked on each other on a solid substrate (1) such as a solid electrolyte and comprising a first layer in contact with the solid substrate and a last layer having a free outer surface intended to be placed in contact with a gas, each of these layers are made up of mixed oxide.    USE - The gas electrode is useful in electrochemical fuel cells (claimed).    ADVANTAGE - The costs and manufacturing techniques of the gas electrode are compatible with industrial scale operation.    DETAILED DESCRIPTION - Gas electrode comprises multiple layers (2, 3, 4) allowing the passage of reactive species through the electrode layers stacked on each other on a solid substrate (1) such as a solid electrolyte and comprising a first layer in contact with the solid substrate and a last layer having a free outer surface intended to be placed in contact with a gas, each of these layers are made up of mixed oxide. The layers are constituted of a mixed oxide, comprising Ruddlesden-Popper phase and perovskites, of formula Ln+1-xNin-yMyO(3n+1 plus minus s) (I). The microstructure of the first layer is different from the microstructure of the last layer. The porosity of different layers increases from the first layer of which the porosity is very low until the last layer of which the porosity is very high. The different layers stacked on each other form a network of solid material interconnected between the external free surface of the last layer and the solid substrate, having a total thickness greater than 1 mu m.    L = rare earths element, preferably La, Pr, Nd, Sm, Eu, Er or Gd;    Ni = nickel;    M = transition metal, preferably Fe, Co or Mn;    n = non-zero integer; and    x, y, s = real numbers i.e. 0 less than or equal to x less than n+1, 0 less than or equal to y less than n and 0 less than or equal to s less than or equal to 0.25.    INDEPENDENT CLAIMS are included for:    (1) the preparation of the gas electrode by stacking the multiple layers on top of each other on the solid substrate i.e. the solid electrolyte, according to the given criteria;    (2) electrochemical cell comprising the gas electrode; and    (3) electrochemical fuel cell, comprising a solid electrolyte carrying a cathode made of the gas electrode.    DESCRIPTION OF DRAWING(S) - The figure shows the cross section of the gas electrode.    Solid electrolyte (1)    First layer (2)    Intermediate layer (3)    Last layer. (4)