Spinel nano-ferrites for aqueous supercapacitors; linking abundant resources and low-cost processes for sustainable energy storage

Spinel nano-ferrite are a remarkably versatile group of metal oxides with unique magnetic and electronic properties as well as huge abundance, low-cost, and high biocompatibility. They are promising materials for addressing sustainable energy conversion and storage as well as the mounting environmental concerns. Although their magnetic and photochemical properties have been widely investigated, their electrochemistry has only recently gained a wide attention and has remained less understood. In the recent years (2016-2020), there have been a surge of reports on the application of nano-ferrites as electrodes in supercapacitors, yet there is no report that is particularly devoted to reviewing and discussing critically the electrochemical performance of the various ferrites (i.e., Fe3O4, MnFe2O4, CoFe2O4, ZnFe2O4, NiFe2O4, and CuFe2O4,) for supercapacitors in different aqueous electrolytes. Herein, first their properties and simple chemical synthesis methods are introduced, and then, their application as supercapacitor electrodes is thoroughly and critically reviewed. Particular attention is given to resolve confusion over inconsistent electrochemical data (e.g., cyclic voltammograms) reported for various nano-ferrites in different electrolytes. Furthermore, it will be revealed that only Fe3O4, MnFe2O4, and CoFe2O4 can behave pseudocapacitive in their respective potential windows, and the other nano-ferrites show either simply an electrochemical double layer capacitor (EDLC) behavior or a battery-type behavior. Finally, concluding remarks, current challenges, and future prospects for supercapacitors based on nano-ferrites will be discussed.

Automated summary

Spinel nano-ferrites are versatile metal oxides with unique properties, making them promising materials for sustainable energy applications. Recent studies have focused on their use as electrodes in supercapacitors, with different ferrites showing varying electrochemical behaviors in aqueous electrolytes.