The Pseudocapacitive Nature of CoFe2O4 Thin Films

Nanostructured Cobalt ferrite (CoFe2O4) thin films are fabricated by aerosol-assisted chemical vapour deposition (AACVD) and studied for application in supercapacitors. XRD and Raman spectroscopic analysis confirms the formation of single phase CoFe2O4. SEM analysis shows that the thin film morphology consists of nanoparticles less than 100nm in size that are sintered together to form larger dendrites raised from the substrate. The larger dendrites range from 0.5–1μm in diameter and are uniformly distributed over the FTO substrate, providing a highly porous structure which is desired for supercapacitor electrodes. Three-electrode electrochemical measurements reveal that CoFe2O4 is pseudocapacitive and is highly conducting. Studies of CoFe2O4 thin films in two-electrode symmetric supercapacitor configuration show a capacitance of 540μFcm−2 and a relaxation time constant of 174ms. Around 80% of the capacitance is retained after 7000 charge-discharge cycles when a maximum charging voltage of 1V was used, indicating that the pseudocapacitive processes in CoFe2O4 are highly reversible and that it exhibits excellent chemical stability in 1M NaOH alkaline electrolyte solution. The results show that CoFe2O4 is a cheap and promising alternative pseudocapacitive material to replace the expensive pseudocapacitive materials.