Facile synthesis of efficient Co3O4 nanostructures using the milky sap of Calotropis procera for oxygen evolution reactions and supercapacitor applications

Adeel Liaquat Bhatti; Aneela Tahira; Shusheel Kumar; Zaheer Ahmed Ujjan; Muhammad Ali Bhatti; Sooraj Kumar; Umair Aftab; Amal Karsy; Ayman Nafady; Antonia Infantes-Molina; Zafar Hussain Ibupoto

doi:10.1039/d3ra02555a

Facile synthesis of efficient Co₃O₄ nanostructures using the milky sap of Calotropis procera for oxygen evolution reactions and supercapacitor applications

RSC Adv. 2023 Jun 16;13(26):17710-17726. doi: 10.1039/d3ra02555a. eCollection 2023 Jun 9.

Authors

Affiliations

¹ Institute of Physics, University of Sindh Jamshoro 76080 Sindh Pakistan zaffar.ibhupoto@usindh.edu.pk.
² Institute of Chemistry, Shah Abdul Latif University Khairpur Mirs Sindh Pakistan.
³ Centre for Environmental Sciences, University of Sindh Jamshoro 76080 Sindh Pakistan.
⁴ Department of Chemical Engineering, Mehran University of Engineering and Technology 7680 Jamshoro Sindh Pakistan.
⁵ Department of Metallurgy and Materials, Mehran University of Engineering and Technology 7680 Jamshoro Sindh Pakistan.
⁶ Nanotechnology Research Centre (NTRC), The British University in Egypt (BUE) Cairo Egypt.
⁷ Chemistry Department, College of Science, King Saud University Riyadh 11451 Saudi Arabia.
⁸ Department of Inorganic Chemistry, Crystallography and Mineralogy, Unidad Asociada al ICP-CSIC, Faculty of Sciences, University of Malaga, Campus de Teatinos 29071 Malaga Spain.
⁹ Institute of Chemistry, University of Sindh Jamshoro 76080 Sindh Pakistan.

Abstract

The preparation of Co₃O₄ nanostructures by a green method has been rapidly increasing owing to its promising aspects, such as facileness, atom economy, low cost, scale-up synthesis, environmental friendliness, and minimal use of hazardous chemicals. In this study, we report on the synthesis of Co₃O₄ nanostructures using the milky sap of Calotropis procera (CP) by a low-temperature aqueous chemical growth method. The milky sap of CP-mediated Co₃O₄ nanostructures were investigated for oxygen evolution reactions (OERs) and supercapacitor applications. The structure and shape characterizations were done by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) techniques. The prepared Co₃O₄ nanostructures showed a heterogeneous morphology consisting of nanoparticles and large micro clusters. A typical cubic phase and a spinel structure of Co₃O₄ nanostructures were also observed. The OER result was obtained at a low overpotential of 250 mV at 10 mA cm^-2 and a low Tafel slope of 53 mV dec^-1. In addition, the durability of 45 hours was also found at 20 mA cm^-2. The newly prepared Co₃O₄ nanostructures using the milky sap of CP were also used to demonstrate a high specific capacitance of 700 F g^-1 at a current density of 0.8 A g^-1 and a power density of 30 W h kg^-1. The enhanced electrochemical performance of Co₃O₄ nanostructures prepared using the milky sap of CP could be attributed to the surface oxygen vacancies, a relatively high amount of Co²⁺, the reduction in the optical band gap and the fast charge transfer rate. These surface, structural, and optical properties were induced by reducing, capping, and stabilizing agents from the milky sap of CP. The obtained results of OERs and supercapacitor applications strongly recommend the use of the milky sap of CP for the synthesis of diverse efficient nanostructured materials in a specific application, particularly in energy conversion and storage devices.