Multifunctional iron-oxide-nanoflake/graphene composites derived from mechanochemical synthesis for enhanced lithium storage and electrocatalysis

Abstract

Composites consisting of nanoparticles of iron oxides and graphene have attracted considerable attention in numerous applications; however, the synthesis methods used to achieve superior functionalities are often complex and unamenable to low-cost large-scale industrial production. Here we report our findings in exploring a simple strategy for low-cost fabrication of multifunctional composites with enhanced properties. In particular, we have successfully prepared FeO(OH)-nanoflake/graphene and nano-Fe3O4/graphene composites from commercially available Fe powders and graphite oxides using a simple and low-cost solid-state process, where the metallic Fe is converted to FeO(OH) nanoflake and graphite oxide is reduced/exfoliated to graphene. The resultant nano-Fe3O4/graphene composite is multifunctional, which demonstrates specific capacities of 802 and 629 mA h g-1, respectively, at 1,000 and 2,000 mA g-1 as an electrode material for lithium-ion batteries (LIB), and further displays efficient catalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER); the nominal overpotentials are lower than those for preciously-reported metal-based catalysts (e.g., IrO2, RuO2 and Pt/C). The dramatically enhanced properties are attributed to the synergistic mechanochemical coupling effects between iron oxide and graphene introduced by the facile process, which is well suited for large-scale cost-effective fabrication.