From Basic Fuchsin to Mixed Dyes: Teaching Electrocatalytic Advanced Oxidation and Digital Image Colorimetry via a Knowledge-Transfer Framework

This article presents an upper-level undergraduate laboratory activity that integrates electrochemistry and environmental chemistry through the electrocatalytic oxidative degradation of the organic dye basic fuchsin (BF). Students assemble a simple two-electrode electrolysis system, operating it under both constant-voltage modes. At the three-dimensional porous nickel-foam cathode, dissolved O2 is reduced via a two-electron pathway to generate H2O2. This H2O2 is subsequently activated at the nickel surface via a reversible Ni2+/Ni3+ redox cycle to yield highly oxidative hydroxyl radicals (•OH), which rapidly degrade BF. Reaction progress is initially monitored qualitatively through time-lapse decolorization. Students then translate these visual changes into semiquantitative trend information using digital image colorimetry. By extracting RGB values from standardized photographs and applying the complementary color principle, students calculate an RGB-derived equivalent absorbance as an operational optical metric, which is compared with UV–Vis spectroscopy to evaluate the degradation trend. Crucially, to foster knowledge transfer, students complete an independent extension task evaluating alternative emerging pollutants to validate the broader applicability of this analytical method. Emphasizing experimental design and variable control, this mechanism-supported, data-driven platform successfully equips students with practical skills in advanced water treatment technologies and accessible analytical techniques.