NOVELTY - The porous cathode (30) comprises an electrically conductive porous support, and a composite material disposed on the support. The composite material comprises a rare earth oxide that is present in part on a surface of the cathode, and metal particles comprising a compound of a metal capable of reacting with a hydride to form a transition metal hydride. The metal particles are partially present on the surface of cathode, and have a size of 10-50 nm. The porous support has a porosity of 40-50%, and is a porous gas diffusion electrode made of carbon.    USE - The porous cathode is useful for reducing carbon dioxide (claimed) by electrocatalysis.    ADVANTAGE - The porous cathode is capable of simply and effectively reducing the carbon dioxide by electrocatalysis hence its catalytic activity is improved.    DETAILED DESCRIPTION - The porous cathode (30) comprises an electrically conductive porous support, and a composite material disposed on the support. The composite material comprises a rare earth oxide that is present in part on a surface of the cathode, and metal particles comprising a compound of a metal capable of reacting with a hydride to form a transition metal hydride. The metal particles are partially present on the surface of cathode, and have a size of 10-50 nm. The porous support has a porosity of 40-50%, and is a porous gas diffusion electrode made of carbon. The composite material comprises an intimate mixture of the rare earth oxide and metal particles in the form of an agglomerate of particles. The composite material further comprises an electronic conductor consisting of carbon black, carbon nanotubes, graphene and pitches. INDEPENDENT CLAIMS are included for:    (1) a process for manufacturing a porous cathode; and    (2) a device for reducing carbon dioxide.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an electrocatalytic device.    Anode (10)    Proton exchange membrane (20)    Cathode (30)    First surface of cathode (33)    Second surface of cathode. (36)