Co3O4 spinel nanoparticles decorated graphite electrode: Bio-mediated synthesis and electrochemical H2O2 sensing

- Extracellular synthesis of single crystalline Co3O4 NPs using analytes present in Sechium edule.
- Weak ferromagnetic Co3O4 NPs of 31.25 nm average diameter tailored on carbon paste electrode for H2O2 sensing.
- Co3O4 NPs surface concentration 5.92 × 10−13 mol/cm2 for Co(OH)2/Co3O4 and, Co3O4/CoOOH redox couple.
- H2O2 detection limit 0.0217 μM and sensitivity 65.32 nA/μM/cm2 was invariant by electroactive species.

The Co3O4 NPs were successfully synthesized by a green synthesis pathway using the analytes extracted from Sechium edule, the fruit of a perennial climber. The analytes, mostly, ascorbic acid, mediated CoOOH transformation to Co(OH)2 and, CoOOH was abundant with Co3O4 NPs in the control condition without these analytes. The structure and morphology of Co3O4 NPs were determined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Atomic force microscopy (AFM), Field emission scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Vibrating sample magnetometer (VSM). The pure Co3O4 NPs confirmed weak ferromagnetic properties. TEM images showed that the Co3O4 NPs have an average diameter size of 31.79 nm. The Co3O4 NPs were tailored on a graphite electrode with an average concentration of 5.92 × 10−13 mol/cm2 to develop a non-enzymatic H2O2 sensor in a phosphate buffer media (pH 7.2). The cyclic voltammetry (CV) technique within the −Ecat = 0.5 to −0.5 V vs. Ag/AgCl showed a low H2O2 reduction peak at −0.117 V with a quasi-reversible electrochemical system. The modified electrode was exhibited a quick amperometric response (<5 s), a low limit of detection (LOD) of H2O2 of 0.0217 μM, and a high electrode sensitivity of 65.32 nA/μM/cm2 and reproducibility (relative standard deviation 3.06%). No alteration of the amperometric responses was noted in the presence of common interferents.