Synthesis and surface engineering of carbon-modified cobalt ferrite for advanced supercapacitor electrode materials

The precise design and surface modification of electrode materials are crucial challenges for advancing the supercapacitor technology. In this study, we report a straightforward two-step process for the synthesis of a cobalt ferrite (CoFe2O4)/carbon hetero nanostructure. The CoFe2O4 nanoparticles were first synthesized using a simple chemical oxidation method, followed by carbon modification using glucose. The modified samples were calcined at 400 and 600 degrees C for 4 h in N2 atmosphere to optimize the structural and electrochemical properties. The increase in the grain size of carbon modified cobalt ferrite magnetic nanoparticles (MNPs) was observed from 22 to 28 nm with post annealing temperature. The presence of carbon was confirmed by the FTIR spectroscopy, FESEM and TEM analyses. The carbon decoration on the cobalt ferrite partially showed a core-shell like morphology. The saturation magnetization of bare cobalt ferrite was observed to be 76 emu/g and the same was decreased by the surface modification with carbon. A high specific capacitance of 323 F/g was observed for the carbon-modified cobalt ferrite MNPs annealed at 600 degrees C. The electrochemical impedance spectroscopy (EIS) analysis demonstrated that the charge-transfer resistance (Rct) decreased significantly in the carbon-modified CoFe2O4 MNPs, particularly for the sample annealed at 600 degrees C, with an Rctvalue of 17 Omega. The carbon layer effectively enhanced conductivity and reduced the electrode/electrolyte interface, led to the improved electrochemical performance, as reflected in the enhanced specific capacitance. An improved capacitance retention of 84 % was achieved in the case of carbon-modified cobalt ferrite MNPs based electrode even after 4000 cycles. The study suggested that the prepared carbon-modified cobalt ferrite MNPs stand in the limelight as a better candidate electrode material for the electrochemical applications.