Extended Data Fig. 6: Bromide electrolysis stability.

The voltage (IR corrected) as a function of time during prolonged galvanostatic measurements at a current of 600 mA in 1.5 M NaBr electrolyte with (red curve) or without 3.8 mM Na₂Cr₂O₇ (all other curves) measured at 60 °C (blue, red and orange curves) or at room temperature (purple and green curves) with (all curves expect for the purple curve) or without stirring (purple curve). Pristine Pt foil or coil (at 60^oC or room temperature, RT, respectively) cathode and RuO₂/TiO₂ DSA anode were used in the measurements, except for the one presented by the orange curve where a pre-coated Pt foil cathode from previous electrolysis tests was used. The voltage drift in the red curve results from changes in the electrolyte composition due to conversion of bromide to bromate during the measurement.