Electrochemical oxygen reduction was carried out in artificial drinking water (ADW). ADW was prepared by dissolving 1 g of sodium bicarbonate, 0.0654 g of magnesium sulphate (Sigma Aldrich, 99.5% anhydrous), 0.3414 g calcium sulphate dehydrate (Honeywell, 99%), 0.007 g potassium phosphate dibasic (Fluka, 98%), potassium phosphate monobasic (Sigma Aldrich, 99%) and 0.01 g sodium nitrate (Sigma Aldrich, 99%) in 10 L of deionised water. ADW was allowed to saturate with oxygen through exposure to air at room temperature (~17 ºC). All oxygen concentrations were measured using a commercial optical DO probe (Hach, LDO101). Both gold-gold (Au-Au) and platinumplatinum (Pt-Pt) IDE arrays were used for this work. CVs were performed in each concentration of oxygen sweeping from 1.2 V to -0.8 V vs. Ag/AgCl at 50 mV/s for 3 cycles. Varying concentrations of hydrogen peroxide solutions (between 20 and 1000 µM) were prepared by diluting a hydrogen peroxide stock (Sigma Aldrich, 30% w/w) with ADW. LSVs were performed in each sample in the voltage range of 0.8 V to -0.2 V vs. Ag/AgCl at 50 mV/s. Scans were performed in triplicate for each concentration.