NOVELTY - The electrochemical cell comprises a porous metal support (41) comprising a first main surface and a second main surface, a porous layer (42) for thermomechanical adaptation on the second main surface, a porous barrier layer (43) for the diffusion of chromium and present on the thermomechanical adaptation layer, a porous hydrogenated electrode layer (44) on the porous barrier layer, a dense electrolyte layer (45) on the porous electrode layer, a dense reaction barrier layer on the electrolyte layer, and an air or oxygen porous electrode layer on the reaction barrier layer.    USE - The electrochemical cell is useful for the electrolysis of water vapor at high temperatures for the production of hydrogen and generation of electricity.    ADVANTAGE - The electrochemical cell ensures economical and large scale production of hydrogen with high performance and reduced emissions of greenhouse gases, avoids the deformations such as cracks in the electrolyte thus improving its life time, and exhibits desired microstructural characteristics such as controlled porosity.    DETAILED DESCRIPTION - The electrochemical cell comprises a porous metal support (41) comprising a first main surface and a second main surface, a porous layer (42) for thermomechanical adaptation on the second main surface, a porous barrier layer (43) for the diffusion of chromium and present on the thermomechanical adaptation layer, a porous hydrogenated electrode layer (44) on the porous barrier layer, a dense electrolyte layer (45) on the porous electrode layer, a dense reaction barrier layer on the electrolyte layer, and an air or oxygen porous electrode layer on the reaction barrier layer. The first and second main surfaces are plane surfaces and parallel. The first main surface is a lower surface, and the second main surface is an upper surface. Layers are stacked on the second main surface. The metal support and the dense layers have a porosity of 20-60 vol.% and lower than 6 vol.% respectively. A distance between the first and second main surfaces is 400-500 mu m. The thermomechanical adaptation porous layer is a metal same as the metal support and an ionic conductor. An INDEPENDENT CLAIM is included for a process for preparation of an electrochemical cell.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross-sectional view of an electrochemical cell.    Metal support (41)    Thermomechanical adaptation porous layer (42)    Chromium diffusion barrier layer (43)    Porous hydrogenated electrode layer (44)    Dense electrolyte layer. (45)