Green solid-state fabrication of new nanocomposites based on La-Fe-O nanostructures for electrochemical hydrogen storage application

Abstract

Nano-sized La-Fe-O (LFO) structures were fabricated via novel free-solvent and green solidstate route using La (acac)3. H2O and Fe (acac)3 complex precursors. Acetylacetonate (acac) in organometallic complex precursors control nucleation and growth of formed crystals with creation spatial barrier around the cations, and prevent nano-product agglomeration. The mechanism of role of acac has been explained in nanostructure formation. Changing of parameters in synthesis reaction consisting La:Fe molar ratio, calcination time and temperature in turn offer a virtuous control over the nanocomposites size and shape which various compositionsof La2O3/LaFeO3, LaFeO3/La2O3 and LaFeO3/Fe2O3 obtained. The as-prepared La-Fe-O nano-products were characterized thorough Scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), X-ray diffraction (XRD), Fourier transforminfrared (FT-IR), UV-Vis, BET and energy dispersive X-ray (EDX) analysis in terms of crystallinity structure, composition, porosity and morphology. Different formed La-Fe-O nanostructures were evaluated for electrochemical hydrogen storage capacity through chronopotentiometry technique in stable current (1mA). The achieved La-Fe-O nanoparticles could be applied as a favorable candidate active material for electrochemical hydrogen storage. Optical, magnetic and reducible characteristics of La-Fe-O nanostructures have positive effect on electrochemical hydrogen storage capacity. It was found out that the LaFeO3/Fe2O3 nanocomposites have the best electrochemical hydrogen storage performance due to oxidation-reduction process of Fe2+/Fe3+ components which can help to charge-discharge process of hydrogen to increase the storage capability to 790 mAhg-1 after 20 cycles. Also, the mixed metal oxides illustrate advanced discharge capacity than other binary oxides.