ORIGINAL PAPER Influence of temperature on the preparation of CoFe 2 O 4 by the sol-gel method and its application in electrochemical energy storage E. C. Silva 1 & J. C. M. da Costa 1 & M. C. Nascimento 1 & B. L. Pereira 1 & R. R. Passos 1 & L. A. Pocrifka 1 Received: 11 December 2019 /Revised: 20 April 2020 /Accepted: 23 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract CoFe 2 O 4 particles were successfully synthesized by a sol-gel proteic route in three different temperatures, and their structural and morphological properties were studied in detail. The XRD pattern results confirmed CoFe 2 O 4 formation with some residual second phase of αCo–Fe in low temperature calcined materials. FTIR spectra showed the strong absorption bands in the range of 440 to 650 cm -1 , which are related to Fe–O and Fe–Co bonds. SEM images illustrated that the cobalt ferrite particles exhibit a porous structure are formed by a hexagonal morphology. It was observed that the increase of calcination temperature resulted in more crystalline and better organized materials. CoFe 2 O 4 specific capacity was 76.52 mA h g -1 at current density of 1 Ag -1 . This was the best result obtained with the 1000 °C material, which was based on the fact that temperature has a great influence on the electrochemical response of cobalt ferrite synthesized by proteic sol gel. It was also observed that 75% of the initial capacity remains the same for 5000 continuous cyclic voltammetry at the scan rate of 25 mVs -1 which confirms the superior performance of the prepared electrode as energy storage material. Keywords Ferrites . Energy storage . Stable structure . Pseudocapacitors Introduction There are renewable and nonrenewable energy resources that supply existing global demand, but it is necessary to assess the limit of these resources, especially nonrenewable ones. Due to globalization, the availability of these nonrenewable sources has been decreasing, their misuse causing environmental ca- tastrophes, and the vast majority of renewable sources are relative to the season, generating the need for materials capa- ble of storing energy [1]. Supercapacitors are energy storage devices capable of pro- viding fast charging, high energy density, and cycling [2]. Applications can already be found where supercapacitors replace common batteries such as chargers, tablets, and power tools. In capacitive materials, there are two modes of energy stor- age, the first through electric double layer and the second by charge transfer at the electrode-electrolyte interface, which obeys Faraday’ s law; the second is called electrochemical pseudocapacity [3]. Currently, supercapacitors dominate research on electronic devices, and despite their widely known advantages, they have major limitations, such as low energy density, for example. Within the group of battery-type materials, it is possible to perceive the degradation of the material during cycling, limit- ing the useful life of the material. It is necessary to develop a new device that will be able to develop energy and energy of high density value. That is, the combination of battery type materials and supercapacitors. Cobalt ferrite has been used extensively for energy storage. The use of this material is due to its excellent electrochemical properties, easy synthesis, low cost, and good theoretical capacity. * L. A. Pocrifka pocrifka@gmail.com 1 Laboratory of Electrochemistry and Energy (LEEN), Chemistryl Graduate Program of Federal University of Amazonas (UFAM), Av. Rodrigo Otávio, 1200, Coroado, Manaus, Amazonas 69067-005, Brazil Journal of Solid State Electrochemistry https://doi.org/10.1007/s10008-020-04616-z