A carbon based electrode for the electrochemical reduction of sulfur or oxygen, which comprises an electrode core and, in electrical contact therewith, a structure comprising a porous particulate activated carbon bonded with a polymeric binder material, characterised in that the structure is at least 1 mm thick, in that the particulate activated carbon is prepared from a lignocellulosic material and has the following properties: i) a particle size in the range of from 200 to 850 &mgr;m; ii) a pore volume of from 0.45 to 1.0 cm3 per gram; iii) a surface area in the range of from 800 to 1500 m2/g; and in that the binder is used in an amount not exceeding 25% by weight based upon the mixture of activated carbon and binder material.