Rational design and solvent-free synthesis of iron-embedded 2D composite materials derived from biomass for efficient oxygen reduction reaction

Abstract

Graphene-like two-dimensional (2D) composite materials, owing to their unique physicochemical features, stand out as suitable catalyst supports for electrocatalytic oxygen reduction reactions (ORR). However, most of these traditional fabrication processes use toxic or expensive chemicals and involve long treatment times and specialized processes. A huge challenge still remains to develop a facile, ecofriendly and sustainable method to fabricate 2D materials from readily available carbon sources. Here, we introduce a universal and scalable solvent-free shearing/carbonization synthetic strategy to fabricate Fe-embedded graphene-like 2D composite materials from biomass and FeCl₃·6H₂O, and demonstrate their performance as efficient and stable ORR electrocatalysts. The coordination derived from the shear exfoliation of biomass, the deliquescent characteristics of FeCl₃·6H₂O, and the carbothermal redox process drives the formation of the Fe-embedded biomass-derived graphene-like 2D composite materials (2DFe/BC). The carbothermal redox process, which is conducive to the etching of the C framework and the formation of the Fe₃C species, endows the as-synthesized 2DFe/BC with abundant active sites and preferentially facilitates electron tunneling, thereby enhancing ORR activity. These morphology and textural features enable the as-synthesized 2DFe/BC electrocatalyst to show remarkable ORR performance and superstability in both alkaline and acid environments, which is comparable with those of the commercial Pt/C (20% wt%) catalyst. Furthermore, many common biomass sources can be used, even biowaste precursors (such as sawdust, tea leaves, wheat straw, carrot, and potato), further confirming that such a concise solvent-free shearing/carbonization method holds promising potential as an effective strategy for the design of graphene-like 2D composite materials for a wide range of applications.