文摘
The large amount of iron rust yielded in steel industries is undoubtedly a useless and undesired product since its substantial formation and recycle/smelting would give rise to enormous financial costs and environmental pollution issues. To best reuse such rusty wastes, we herein propose a smart and applicable method to convert them into uniform α-Fe<sub>2sub>O<sub>3sub> nanospheres. Only after a simple and conventional hydrothermal treatment in HNO<sub>3sub> solution, nearly all of the iron rust can evolve into sphere-like α-Fe<sub>2sub>O<sub>3sub> products with a typical size of ∼30 nm. When serving as actives for electrochemical energy storage, the in situ generated α-Fe<sub>2sub>O<sub>3sub> nanospheres exhibit prominent anodic performance, with a maximum specific capacity of ∼269 mAh/g at ∼0.3 A/g, good rate capabilities (∼67.3 mAh/g still retains even at a high rate up to 12.3 A/g), and negligible capacity degradation among 500 cycles. Furthermore, by paring with activated carbons/Ni cathodes, a unique full hybrid Ni–Fe cell is constructed. The assembled full devices can be operated reversibly at a voltage as high as ∼1.8 V in aqueous electrolytes, capable of delivering both high specific energy and power densities with maximum values of ∼131.25 Wh/kg and ∼14 kW/kg, respectively. Our study offers a scalable and effective route to transform rusty wastes into useful α-Fe<sub>2sub>O<sub>3sub> nanospheres, providing an economic way to make sustainable anodes for energy-storage applications and also a platform to develop advanced Fe-based nanomaterials for other wide potential applications.