Electrochemical testing was carried out using the ME-cell (shown in Figure in the main manuscript) and a laboratory-electrolyser-cell (LE-cell) with a 5 cm 2 active area which has been previously reported. Both were supplied with KOH(aq) (1 M) feed solution at the anode and cathode using a peristaltic pump while the flow rates deferred at 7.8 mL min -1 from two 250 mL reservoirs and 40 mL min -1 from two 1 L reservoirs for the ME and LE-cell, respectively. The solution was preheated using stainless steel tubing submerged in a water bath to achieve an anode outlet temperature of 40 °C measured using an in-line K-type thermocouple. Electrochemical measurements were performed using Gamry Interface 1000 and 5000E potentiostats.