PANI/Co3O4 composite material connected by coordination and hydrogen bonds for the elevation of rate charge/discharge capability

Abstract

In this investigation, PANI/Co₃O₄ composite material with good rate charge/discharge capability was prepared through chemical grafting polyaniline (PANI) on the surface of homogeneous nucleated Co₃O₄. he physical properties were characterized by XRD, IR, XPS, SEM, EDS and N₂ adsorption/desorption measurements. The charge/discharge performance was evaluated in 6 M KOH electrolyte using a symmetrical two-electrode configuration. The results show that Co₃O₄ has a face-centered cubic crystal structure with both Co²⁺ and Co³⁺ ions present in its lattice. After the modification, PANI particles covered the surface of Co₃O₄. Furthermore, PANI was bonded to Co₃O₄ via coordination and hydrogen bonds. Compared with Co₃O₄, the PANI/Co₃O₄ composite exhibits a 5.2 % increase in N content. Moreover, N atoms exist in PANI/Co₃O₄ as -${\mathrm{NH}}^{+·}$-, -NH- and = N- species. The PANI/Co₃O₄ composite has a specific surface area of 22 m²/g and a pore volume of 0.129 cm³/g, which are 1.57 times and 1.79 times those of pure Co₃O₄, respectively. In KOH electrolyte, the electrochemical behavior of PANI/Co₃O₄ is dominated by both surface control and ion diffusion processes. At a scan rate of 200 mV/s, the pseudocapacitive contribution of PANI/Co₃O₄ reaches 79.5 %, which is 3.2 % higher than that of Co₃O₄. Compared with Co₃O₄, PANI/Co₃O₄ displays a good rate charge/discharge performance. At 0.1 A/g, the energy density of PANI/Co₃O₄ is 6.7 Wh/kg. When the current density is enhanced to 5 A/g, the energy density retention is 43.4 %. This value is 1.18 times that of Co₃O₄, which is closely associated with the improved pore structure and the connection type between PANI and Co₃O₄.