Photoelectrochemical sensing and mechanism investigation of hydrogen peroxide using a pristine hematite nanoarrays

In this paper, a facile hydrothermal combined with subsequent two-step post-calcination method was used to fabricate hematite (α-Fe₂O₃) nanoarrays on fluorine-doped SnO₂ glass (FTO). The morphology, crystalline phase, optical property and surface chemical states of the fabricated α-Fe₂O₃ photoelectrode were characterized by scanning electron microscopy, X-ray diffraction, ultraviolet visible spectroscopy and X-ray photoelectron spectroscopy correspondingly. The α-Fe₂O₃ photoelectrode exhibits excellent photoelectrochemical (PEC) response toward hydrogen peroxide (H₂O₂) in aqueous solutions, with a low detection limit of 20 μM (S/N = 3) and wide linear range (0.01-0.09, 0.3-4, and 6-16 mM). Additionally, the α-Fe₂O₃ photoelectrode shows satisfying reproducibility, stability, selectivity and good feasibility for real samples. Mechanism analysis indicates, comparing with H₂O, H₂O₂ possesses much more fast reaction kinetics over α-Fe₂O₃ surface, thus the recombination of photogenerated charges are reduced, followed by much more photogenerated electrons are migrated to the counter electrode via external circuit. The insight on the enhanced photocurrent, which is corelative to the concentration of H₂O₂ in aqueous solution, will stimulate us to further optimize the surface structure of α-Fe₂O₃ to gain highly efficient α-Fe₂O₃ based sensors.