Hierarchically Structured Ferric Oxides Derived from Fe-MOF-5-Wood for Scalable Cathodic H2O2 Electrochemical Synthesis

Abstract

Existing fossil-fuel-derived electrocatalysts still pose huge challenges in terms of cost-effective operation, safety, renewability, and ecological sustainability. Here, we demonstrate a simple effective strategy to construct a nanostructured wood-Fe-MOF-5 as a high-performance electrocatalyst for the air-cathodic electrosynthesis of scalable H₂O₂. Through coordinating of organic iron into regular MOF-5 in situ growing around the abundant oxygen-containing xylem cell walls vertically aligned within natural wood, we obtain a unique biconical hexagonal prism Fe-MOF-5 structure with a high specific surface area. The rapid gasification of Zn²⁺ pyrolytically dissociated from wood-Fe-MOF-5 modulates the catalytic electron structure of micro-mesoporous hollow ferric oxides (50–200 nm, hybrid Fe₂O₃/Fe₃O₄), enabling abundant carbon defects and oxygen vacancies offered by unsaturated coordinated Fe–O₄. This catalyst achieves a highly selective 2e^– oxygen reduction reaction (84.5%), boosting H₂O₂ production to 264.0 mg L^–1 in the cathodic chamber using ambient air. Its production efficiency surpasses that of existing biochar-based electrocatalysts by up to 100 times. This strategy shows also universality to other lignocellulosic wastes such as bamboo and corn straw, manifesting also a huge potential in scalable H₂O₂ production.