Carbon-decorated iron oxide hollow granules formed using a silk fibrous template: Lithium-oxygen battery and wastewater treatment applications

Hierarchical nanoarchitecture and phase control of iron oxides are important approaches for achieving multi-functionality for various applications. Herein, rice-grain-shaped iron oxide hollow structures were synthesized via a hydrothermal process using a silk fibrous template, and the crystalline phases (α-Fe 2 O 3, Fe 3 O 4) were controlled by annealing. These structures were applied in a lithium-oxygen battery cathode and as adsorbents for wastewater treatment. The porosity, hollow interior, surface area, surface chemical composition and efficient carbon matrix of the C/Fe 3 O 4 hollow granules obtained by annealing under Ar atmosphere were favorable for enhancing the oxygen reduction and evolution kinetics when applied as an electrocatalyst for lithium-oxygen batteries, and also led to superior adsorption of organic pollutants (Rhodamine B) from an aqueous medium. The C/Fe 3 O 4 hollow granules were uniformly distributed and confined in the 3D nanoarchitecture; this morphology can offer rapid ion transport with improved electronic and chemical kinetics as well as superior adsorption of organic pollutants.