The Chemical and Physical alteration of Nafion Membranes for Use in Reversible Electrolyses to Generate Hydrogen

The reverse electrolyser is an electrochemical system designed to work in either electrolyser mode or fuel cell mode. The system harnesses energy from renewable sources during times of surplus, and uses that energy to catalytically convert water into hydrogen, using Ce(III) and (IV) as the active catalyst dissolved in methanesulphonic acid. The major flaw with the current system is the ion exchange membrane, made from Nafion, used to conduct protons from anode to cathode. Currently this membrane is not selective for protons alone, meaning other ions in the system can be conducted across the membrane and can short circuit the system as well as become trapped in the Nafion hydrophilic channels increasing the resistance of the membrane and hence will decrease the current the electrolyser can achieve. This study has involved altering the Nafion membrane either chemically using polyethylenimime, or electrostatically using negative and positive polymer solutions. The goal was to improve selectivity for protons and reject metal ions (specifically cerium ions) and hence enhance output performance by avoiding increase of resistance from metal ions migrating into membrane following proton current flow. This has proved reasonably successful finding membranes that are vastly better at rejecting metal ions whilst still able to maintain a high current. Further studies using more durable electrodes, a more concentrated electrolytic solution and for a longer period of time will need to be carried out before these new membranes can be used commercially.