To prepare nominally duplicate electrodes, two GDE samples were extracted from a PTFE GDL sheet (0.45 µm Aspire Laminated membrane from lot# 685459, Sterlitech corporation) coated with ca. 300 nm of evaporated Cu. Each GDE was operated using a sequence of cyclic voltammetry (CV) and chronoamperometry (CA) experiments, with the CVs assessing the time-resolved product analysis and the CAs used for product quantification and evaluation of reproducibility between comparable experiments with the nominally duplicate electrodes.