The present disclosure relates to electrolysis. Teachings thereof may be embodied in a reduction method and/or an electrolysis system for electrochemical carbon dioxide utilization. For example, an electrolysis system for carbon dioxide utilization may include: an electrolysis cell with an anode in an anode space, a cathode in a cathode space, and a membrane; a first feed for carbon dioxide into the cathode space, configured to bring the carbon dioxide into contact with the cathode; a proton donor unit; and a second feed for protons configured to bring the protons into the cathode space from the proton donor unit into contact with the cathode.