Abstract
The carbon supported iron selenide catalysts (FeSe2/C) were prepared with various selenium to iron ratios (Se/Fe), namely, Se/Fe = 2.0, 2.5, 3.0, 3.5 and 4.0, through facile microwave route by using ferrous oxalate (FeC2O4·2H2O) and selenium dioxide (SeO2) as precursors. Accordingly, effects of Se/Fe ratio on the crystal structure, crystallite size, microstructure, surface composition and electrocatalytic activity for oxygen reduction reaction (ORR) of FeSe2/C in an alkaline medium were systematically investigated. The results revealed that all the FeSe2/C catalysts obtained with the Se/Fe ratios of 2.0–4.0 exhibited almost pure orthogonal FeSe2 structure with the estimated mean crystallite sizes of 32.9–36.2 nm. The electrocatalytic activities in potassium hydroxide solutions were higher than those in perchloric acid solutions, and two peak potentials or two plateaus responded to ORR were observed from cyclic voltammograms and polarization curves, respectively. The ORR potentials of 0.781–0.814 V with the electron transfer numbers of 3.3–3.9 at 0.3 V could be achieved as the Se/Fe ratios varied from 2.0 to 4.0. The Fe and Se were presented at the surface of FeSe2/C upon further reduction on FeSe2. The Se/Fe ratios slightly influenced the degree of graphitization in carbon support and the amount of active sites for ORR.
Highlights
Alkaline fuel cells have been attracting extensive attention due to their great advantages in cathode dynamics and with the reduction of ohmic polarization [1]
The onset potential of 0.823 V for ORR could be attained in H2SO4 solutions with CoSe/C synthesized through microwave assisted routes [16], while the ORR potentials of 0.6–0.7 V and the electron transfer numbers of 3.1 Oxygen reduction reaction 4.0 could be obtained for CoSe2/C prepared with the Se/Co ratios of
The crystal phases, microstructures, chemical compositions and electrocatalytic activities of the as-prepared FeSe2/C catalysts were explored by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and rotating disk electrode (RDE) techniques
Summary
Alkaline fuel cells have been attracting extensive attention due to their great advantages in cathode dynamics and with the reduction of ohmic polarization [1]. The onset potential of 0.823 V for ORR could be attained in H2SO4 solutions with CoSe/C synthesized through microwave assisted routes [16], while the ORR potentials of 0.6–0.7 V and the electron transfer numbers of 3.1 Oxygen reduction reaction 4.0 could be obtained for CoSe2/C prepared with the Se/Co ratios of. A series of carbon supported FeSe2 nanoparticles were synthesized using the microwave method with different molar ratios of Se/Fe. The crystal phases, microstructures, chemical compositions and electrocatalytic activities of the as-prepared FeSe2/C catalysts were explored by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and rotating disk electrode (RDE) techniques. The effect of Se/Fe ratio on ORR activity in an alkaline medium is discussed in terms of ORR active site and carbon graphitization
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