Fe₂O₃ Nanoparticle/SWCNT Composite Electrode for Sensitive Electrocatalytic Oxidation of Hydroquinone

This article reports a composite electrode of Fe₂O₃ nanoparticles/SWCNTs for hydroquinone electrochemical sensing. The synthesis includes the wet-chemical synthesis of Fe₃O₄ nanoparticles and the assembly of Fe₃O₄ nanoparticles onto single walled carbon nanotubes. Fe₃O₄/NH₂-CNTs composite is formed via the electrostatic attraction between positively-charged ammonia-terminated CNTs and negatively-charged Fe₃O₄ nanoparticles. Subsequent heat treatment oxidizes Fe₃O₄ to Fe₂O₃. The composite can be applied onto FTO glass to form Fe₂O₃/CNTs/FTO electrode and the electrode shows good performance in electrochemical sensing of hydroquinone as compared to Fe₂O₃/FTO and CNTs/FTO electrodes. SEM and TEM results show the iron oxide NPs were uniformly dispersed onto the surface of SWCNTs. The iron oxide NPs which uniformly anchored on the SWCNTs could accelerate the electron transfer rate which was evidenced by electrochemical impedance spectroscopy. The enhancement of electrochemical response further confirms the synergy between Fe₂O₃ NPs and SWCNTs. Differential pulse voltammetry was successfully used to quantify hydroquinone within the concentration range of 1.0∼80.0 μM under optimal conditions. The detection limit of Fe₂O₃/CNTs/FTO electrode for hydroquinone was 0.50 μM (S/N = 3). The electrode was further applied to test for hydroquinone in tap water and the Fe₂O₃/CNTs/FTO electrode also presents good stability and high reproducibility, proofing the potential of Fe₂O₃/CNTs electrode as a promising electrochemical sensor. This work presents an electrode using FTO substrate for the first time. It shows that FTO can be a potential alternative to glassy carbon electrode with lower cost, but without compromising too much on the sensitivity.