An electrolyser including a stack of a plurality of elementary electrolysis cells, each cell including a cathode, an anode, and an electrolyte provided between the cathode and the anode. An interconnection plate is interposed between each anode of an elementary cell and a cathode of a following elementary cell, the interconnection plate being in electric contact with the anode and the cathode. A pneumatic fluid is to be brought into contact with the cathodes, and the electrolyser further includes a mechanism ensuring circulation of the pneumatic fluid in the electrolyser for heating it up before contacting the same with the cathodes.