Electrolyte pH conditioning of Regenesys®

Regenesys® is a regenerative fuel cell based on the sulphur and sodium bromide redox couple. On charging the system sulphur (polysulphide) is reduced to the sulphide and bromide oxidised to bromine. During discharge or power delivery the sulphide is oxidised back to sulphur (polysulphide) and the bromine reduced back to the bromide The bromide electrolyte pH decreases during operation. This is symptomatic of the chemical imbalance within the system. HS- is transported across the membrane where oxidisation by the bromine ultimately yields sulphuric acid. Back diffusion of protons will occur if low pH is maintained. The result is the neutralisation of the polysulphide electrolyte (HS- and OH-) and consequently the inhibition of the hydroxyl dependent discharge process that decreases the discharge capacity. [Continues.]