Synthesis and electrochemical performance of Cr-Mn3O4/PANI and Co-Mn3O4/PANI ternary nanocomposites for supercapacitor applications

Cr- and Co-doped Manganese oxide (Cr-Mn₃O₄ and Co-Mn₃O₄) was synthesized by facile auto combustion technique and inserted into the polyaniline (PANI) matrix to prepare Cr-Mn₃O₄/PANI and Co-Mn₃O₄/PANI ternary nanocomposites via in-situ oxidative polymerization method. The role of transition metal dopants and PANI on the composite’s crystal structure, morphology, and electrochemical properties was investigated systematically. The crystalline phase of the doped composite was identified using X-ray diffraction, while morphological evaluation of the composite was assessed using a scanning electron microscope, revealing a uniform coating of PANI on doped Mn₃O₄ particles. Electrochemical analysis indicated that metal doping and PANI incorporation significantly enhanced the electrochemical properties of the ternary nanocomposites. Doping with spinel-structured transition metal oxides improved phase stability during cyclic charge-discharge and charge-transfer behavior. Among the electrodes studied, the Co-Mn₃O₄/PANI nanocomposite achieved the highest specific capacitance at 1024.9 F/g at a current density of 0.5 A/g, an energy density of 22.8 Wh/kg, and a power density of 690 W/kg. Supercapacitor devices were then fabricated using the nanocomposite as the negative electrode and graphite (Gr) as the positive electrode. The Co-Mn₃O₄/PANI//Gr device demonstrated superior performance, reaching a capacitance of 300 F/g. This high performance is attributed to the interaction between Co-Mn₃O₄ and the PANI backbone, confirming that doping enhances the capacitive properties of spinel-structured transition-metal oxides. Co-Mn₃O₄/PANI nanocomposites are thus promising candidates for high-capacity supercapacitors.