Enhancing oxygen reduction reaction activity of ε-MnO2 nanoparticles via iron doping

Abstract

In this study, 3D flower-like MnO2 and Fe–MnO2 nanoparticles were developed using a co-perception method. In the doping manner, the concentration of Fe was raised from 0.025 M to 0.125 M in levels of 0.025 M. The prepared electrocatalysts were calcined at 500 °C. Different analytical techniques, particularly XRD, SEM, UV–Vis, FTIR, TGA/DTA, CV, ICP-OES, BET, and LSV were utilized to analyze the structure, morphology, optical, thermal, and electrochemical activity of 3D flower-like MnO2 and Fe–MnO2 nanoparticles. XRD analysis showed the phase change from ε to λ and the phase of MnO2 and the crystallite sizes of un-doped MnO2 and Fe–MnO2 were between 1.18 and 2.25 nm. Morphological examinations indicated that pure MnO2 and Fe-doped MnO2 have spherical-like flake-flower and agglomerated nanoparticle architectures, respectively. The BET surface area of 0.125 M Fe–MnO2 nanoparticles is 288.2 m2g-1. The bandgap energies of MnO2, 0.05 M Fe-doped MnO2, and 0.125 M Fe-doped MnO2 nanoparticles were determined to be 0.57 eV, 0.18 eV, and 0.14 eV, respectively as evident from UV–Vis. The presence of M − O bonds (M = Mn, Fe) was analyzed by FTIR spectroscopy. The doped MnO2 electrocatalyst shows improved thermal properties owing to the doping effect of iron. The results of CV and LSV measurements reveal that the Fe–MnO2 nanoparticles have an excellent catalytic performance toward the ORR under 0.1 M KOH alkaline conditions.