Green synthesis of lead oxide nanostructures using Passiflora edulis peel extract and investigation of their electrochemical response toward ethanol oxidation

An aqueous Passiflora edulis peel extract was used to prepare lead oxide nanostructures, which were then tested as modifiers of carbon paste electrodes for ethanol oxidation in acidic medium. Structural, thermal, and morphological features were examined by ultraviolet-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The synthesized material consisted of a Pb3O4-rich mixed lead oxide system with lamellar morphology and surface-associated phytochemical residues. Among the tested compositions, the electrode containing 5 wt% oxide combined the highest apparent electroactive area with the favorable voltammetric response. The ethanol-oxidation response depended strongly on electrolyte acidity and reached its highest value in 0.5 mol L−1 sulfuric acid (pH ≈ 0.3). Scan-rate analysis suggested a mixed response with an important diffusion contribution and interfacial surface effects. Chronoamperometry and continuous cycling showed that the modified electrode retained electrochemical activity over the test period, whereas impedance measurements at open-circuit potential were consistent with a comparatively low interfacial charge-transfer barrier.These results indicated that Passiflora edulis peel extract can be used as a biomass-derived reagent for the preparation of lead oxide nanostructures for ethanol oxidation studies.