Electrochemical performances of MnO₂/Fe₃O₄/activated carbon ternary composites for supercapacitor and direct ethanol fuel cell catalyst application

MnO₂ and Fe₃O₄ nanoparticles' slow ion-diffusion kinetics and weak electrical conductivity hinder their electrochemical performance in supercapacitors and their energy-conversion ability in direct ethanol fuel cells (DAFCs). Combining MnO₂/Fe₃O₄ with biomass-based activated carbon (AC), which is conductive, inexpensive, and has a long cycle life, to create MnO₂/Fe₃O₄/AC can improve their electrochemical performances for ethanol oxidation and in supercapacitors. Herein, MnO₂/Fe₃O₄/AC ternary composites were synthesized <i>via</i> a facile method. The physicochemical and electrochemical properties of pure and composite materials were characterized using TGA-DTA, XRD, FTIR, BET, SEM-EDX, TEM, HRTEM, SAED, CV, and EIS. The composite MnO₂/Fe₃O₄@8%AC exhibited the highest specific capacitance, with a value of 515.113 F g^-1 at 1 A g^-1. Furthermore, in cyclability tests, after 700 cycles at a current density of 1 A g^-1, its charge-storage performance showed an 81.83% capacity retention and a maximum energy density of 27.679 W h kg^-1. Upon integration in a DAFC, MnO₂/Fe₃O₄@8%AC electrocatalytic ethanol oxidation was achieved with a maximum power density of 44.41 mW cm^-2, indicating better performance than that of other pure and composite catalysts. Therefore, this work provides a potential candidate for use in efficient energy-storage devices and an effective catalyst electrode for the ethanol oxidation reaction.