Synthesis And Electrochemical Properties Of Iron-based Nanocomposites

In recent years,with environmental pollution and depletion of fossil fuels,we need to find a clear energy supply and efficient energy conversion to reduce the dependence on fossil energy and improve energy efficiency.Therefore,to improve the charge storage performances of supercapacitors and catalytic activities of water electrolysis industry have become the research center.Transition metal oxides and sulfides have attracted growing research attention in the fields of catalysis/energy storage owing to their earth-abundance,low cost.Especially,transition metal-based compounds containing a variety of metal components have excellent catalytic/sensing/energy storage performances due to the strong synergistic effects between components.Developing high efficient electrocatalysis and electrochemical energy storage materials become a hot research topic by utilizing the synergistic effect.In this study,with iron based composite nanocomposites as research objects,Fe₃O₄@Co₉S₈/reduced graphene oxide composite electrocatalysts and porous Fe-Mn-O nanocomposite materials were successfully synthesized.All products were systematically characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,and other means.The properties of Fe₃O₄@Co₉S₈/reduced graphene oxide composites used as electrocatalysts of oxygen evolution reaction and porous Fe-Mn-O nanocomposites used as electrode materials of supercapacitor were investigated.The details are as follows:1.A facile solvothermal method was developed for the synthesis of Fe₃O₄ decorated Co₉S₈/ reduced graphene oxide composites?Fe₃O₄@Co₉S₈/rGO?.It was found that the introduction of iron component could affect the phase of cobalt sulfide in the composites.The composite exhibits enhanced electrocatalytic oxygen evolution due to the synergistic effects.We found Fe₃O₄@Co₉S₈/rGO catalyst afforded a current density of 10 m A cm-2 at a small overpotential of a mere 0.34 V and a Tafel slope of ⁵4.5 mV decade-1 in 0.1 M KOH solution,which is far better than the performance of precious cobalt sulfide catalysts.In addition,this Fe₃O₄@Co₉S₈/rGO catalyst also presents outstanding durability under OER cycling conditions.Based on the results of XPS analysis,in the Fe₃O₄@Co₉S₈/rGO catalyst,the electron transfer trend from Fe species to Co₉S₈ promotes the breaking of the Co-O-O bond attributing to the excellent catalytic activity.2.With tartaric acid as a complexing agent,Fe-Mn-O nanocomposite materials were synthesized by a calcination-assistant polymer precursor route.In the composites,iron and manganese are uniformly distributed,and the porous structure with the BET surface area of 72.7 m2 g-1 was characterized.When used as supercapacitor electrode in neutral solution,the Fe-Mn-O composites exhibit an extremely wide working potential window from-0.2 to 1.0 V?vs.SCE?,and a specific capacitance as high as 86.7 F g-1 was observed at the current density of 1 A g-1 with good cycle life.