Deep eutectic solvent-assisted synthesis of transition metal oxide and its integration into polymer matrix for supercapacitor

Transition metal oxide-based materials continue to attract interest in energy and environmental applications due to their unique characteristics. However, their integration with polymers needs to be explored to achieve enhanced capacitance values. To address this issue, two step strategy is utilized wherein the first step involves preparation of a pristine transition metal oxide (Co₃O₄) by a deep eutectic solvent (DES) consisting of choline chloride and hydrogen donor ethyelene glycol in the ratio of 2:1. In the second step the environmentally friendly high energy ball milling is utilized with strong mechanical forces producing desired poly-3-dodecyl thiophene (P3DDT)-wrapped cobalt oxide (Co₃O₄). The structural and morphological properties of the prepared Co₃O₄ and its composite (P3DDT-Co₃O₄) are determined by aid of X-ray diffraction (XRD) studies, Field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS). The synthesized Co₃O₄ exhibited petal-like morphology, whereas in P3DDT-Co₃O₄ the polymer appears to be completely wrapped on transition metal oxide. The electrochemical characteristics of electrodes were studied. The P3DDT-Co₃O₄ exhibited higher specific capacitance (294F/g) than pristine Co₃O₄ (174F/g) at a current density of 1 A/g and its retention capacity increased (96%) and then decreased (93%) over 5000 cycles in a three-electrode cell assembly. The lowest capacitance (136F/g) was obtained for P3DDT. Experimental results demonstrate that the design is suitable for upgrading favorably active electrochemical spots in Co₃O₄ during the incorporation of P3DDT by the ball-milling procedure, showing outstanding performance in energy-storage applications.