Abstract
Two Fe–Mn bimetallic oxides were synthesized through a facile solvothermal method without using any templates. Fe2O3/Mn2O3 is made up of Fe2O3 and Mn2O3 as confirmed via XRD. TEM and HRTEM observations show Fe2O3 nanoparticles uniformly dispersed on the Mn2O3 substrate and a distinct heterojunction boundary between Fe2O3 nanoparticles and Mn2O3 substrate. MnFe2O4 as a pure phase sample was also prepared and investigated in this study. The current densities in CV tests were normalized to their corresponding surface area to exclude the effect of their specific surface area. Direct methanol fuel cells (DMFCs) were equipped with bimetallic oxides as cathode catalyst, PtRu/C as the anode catalyst and PFM as the electrolyte film. CV and DMFC tests show that Fe2O3/Mn2O3(3 : 1) exhibits higher oxygen reduction reaction (ORR) activity than Fe2O3/Mn2O3(1 : 1), Fe2O3/Mn2O3(1 : 3), Fe2O3/Mn2O3(5 : 1) and MnFe2O4. The much superior catalytic performance is due to its larger surface area, the existence of numerous heterojunction interfaces and the synergistic effect between Fe2O3 and Mn2O3, which can provide numerous catalytic active sites, accelerate mass transfer, and increase ORR efficiency.
Highlights
The rapid depletion of fossil fuel and the increase in environmental pollution have driven us to search for sustainable and clean energy resources
Cyclic voltammetry (CV) and Direct methanol fuel cells (DMFCs) tests show that Fe2O3/Mn2O3(3 : 1) exhibits higher oxygen reduction reaction (ORR) activity than Fe2O3/Mn2O3(1 : 1), Fe2O3/Mn2O3(1 : 3), Fe2O3/ Mn2O3(5 : 1) and MnFe2O4
The TEM and HRTEM images show Fe2O3 nanoparticles uniformly dispersed on the Mn2O3 substrate and a distinct heterojunction boundary between Fe2O3 nanoparticles and Mn2O3 substrate
Summary
The rapid depletion of fossil fuel and the increase in environmental pollution have driven us to search for sustainable and clean energy resources. Transition metal (Fe, Co, Ni, Mn, etc.) oxides have gained increasing interest as ORR catalysts in virtue of their high activity, low cost and environmental friendliness.[21] In recent years, numerous studies have focused on binary and ternary metal oxides because of their good synergistic effects and good cycle stability. The catalytic activity of MnFe2O4 is higher than that of Fe2O3 The TEM and HRTEM images show Fe2O3 nanoparticles uniformly dispersed on the Mn2O3 substrate and a distinct heterojunction boundary between Fe2O3 nanoparticles and Mn2O3 substrate. The alkaline DMFCs were assembled using Fe2O3/Mn2O3 or MnFe2O4 as cathode catalyst, PtRu/C as anode catalyst, and PFM instead of PEM. CV and DMFC performance tests indicate that the ORR catalytic activity of Fe2O3/Mn2O3 is superior to that of MnFe2O4. X-ray photoelectron spectroscopy (XPS) measurements (VG Thermo ESCALAB 250 spectrometer) were used to quantitatively analyze the chemical compositions of samples
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