A highly sensitive non-enzymatic hydrogen peroxide and hydrazine electrochemical sensor based on 3D micro-snowflake architectures of α-Fe2O3

Abstract

In the present work, well crystalline 3D micro-snowflake structured α-Fe₂O₃ has been successfully synthesized on a large scale via a simple hydrothermal reaction by hydrolysis of a K₃Fe(CN)₆ precursor. The structure, composition, purity and morphology of the synthesized α-Fe₂O₃ samples are examined using powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and Mössbauer spectroscopy. The FESEM and TEM images reveal that the sample exhibits a micro-snowflake like shape having six-fold symmetry with symmetric branching along each arm consisting of a long central trunk and secondary branches. The 3D micro-snowflake structured α-Fe₂O₃ embedded ITO electrode exhibits high selectivity and sensitivity for electrochemical probing of hydrogen peroxide (H₂O₂) and hydrazine (N₂H₄) with a very low detection limit in a wide linear range. Amperometric measurements show a sensitivity of 7.16 μA mM⁻¹ cm⁻² in a wide linear range from 0.1 to 5.5 mM with the lowest detection limit of 0.01 mM (S/N = 3) towards H₂O₂ sensing. The sample also exhibits a sensitivity of 24.03 μA mM⁻¹ cm⁻² in the linear range between 50 μM and 1340 μM with the lowest detection limit of 5 μM towards hydrazine detection. The excellent electrochemical activity of the sample is rendered to the presence of a large number of catalytic sites in the sample due to its 3D micro-snowflake like architecture. Good reproducibility, stability and selectivity suggest its suitability for the fabrication of H₂O₂ and hydrazine sensors.