Preparation of nano-Co3O4-coated Albizia procera-derived carbon by direct thermal decomposition method for electrochemical water oxidation

Abstract

It is obtained that nano-Co3O4-coated carbon prepared by thermal decomposition of Co(NO3)2·6H2O at 300 °C on home-made Albizia procera (Roxb.) leaves derived carbon is an efficient electrocatalyst for electrochemical water oxidation in 0.1 M NaOH (aq.) solution. The loading of nano-Co3O4 on the carbon was changed by varying the amount of precursor of cobalt (100–1000 mg) and using a constant amount of the carbon (200 mg) during thermal decomposition. The prepared samples were characterized by physical techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), thermo-gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). XRD, TEM, FESEM, and EDS confirmed the formation of uniformly distributed nanoparticles of single-phase Co3O4 on the surface of carbon. The XRD data reveals formation of nano-Co3O4 with average particle sizes in the range of 9–17 nm. The FESEM micrographs demonstrate that Co3O4 nanoparticles, having irregular morphology, are uniformly and densely covered on the surface of supporting carbon.. The prepared samples were immobilized on the filter paper derived carbon electrode (FPCE) to study their electrocatalytic properties toward water oxidation. The cyclic voltammetric studies showed that the nano-Co3O4-C prepared using 400 mg of Co(NO3)2·6H2O (nano-Co3O4-C-400), which possesses meso- and macropores with BET surface area of 192.4 m2/g, reaches a current density of 28 mAcm−2 at 1.5 V and electrochemical water oxidation starting potential of 0.7 V. In this work, it is also shown that the current densities, at 1.5 V, increase by increasing the amount of cobalt oxide in the prepared samples though. The nano-Co3O4-C-400 catalyst shows optimum performance for electrochemical water oxidation in terms of starting water oxidation potential, reasonable amount of Co3O4 and moderate level of current density at 1.5 V.