Abstract: Disclosed is an energy efficient electrolyzer for the production of hydrogen. The electrolyzer consists of an inner container, a plurality of electrolytic cells within the container and means for passing electric current in series through the electrolytic cells. Each cell consists of the anode half of one inert impervious conducting bipolar plate, in contact with an inert conductive anode bed of large surface area separated from the facing cathode half of another inert impervious conducting bipolar plate by a porous insulating separator. The anode is impregnated with an anolyte of about 10 to about 60% aqueous sulfuric acid saturated with sulfur dioxide and the cathode is bathed in a catholyte of about 10 to about 60% aqueous sulfuric acid. The anode is preferably carbon pellets which have been obtained from vegetable matter and which contain about 1 to about 5% platinum.