Hetero-structured Fe–Cr–O hollow multishelled spheres for stable sodium storage

Abstract

Hollow multishelled structures (HoMSs) are applicable in a diversity of fields, owing to their unique properties like large surface areas and buffering effect. Although metal oxide HoMSs with various compositions have been reported, the facile synthesis of hetero-structured HoMSs with more than one component is challenging. Herein, the construction of iron–chromium–oxide (Fe–Cr–O) HoMSs is achieved through the sequential templating approach. Three representative structures are obtained by controlling the Fe/Cr molar ratio, including unitary Fe₂O₃ or Cr₂O₃ HoMSs, Fe–Cr–O solid solution HoMSs, and hetero-structured Fe–Cr–O HoMSs. The hetero-structured HoMSs are composed of Fe–Cr–O solid solution walls with the decoration of Cr₂O₃-rich crystals. In situ XRD results reveal that Fe(III) is active while Cr(III) is inactive. However, the introduction of Cr(III) could stabilize the structure. As a result, the Fe₂O₃ HoMSs deliver the highest capacity, and the Fe–Cr–O–2/2 HoMSs demonstrate a trade-off between capacity and durability.