Evolution of Useless Iron Rust into Uniform α-Fe₂O₃ Nanospheres: A Smart Way to Make Sustainable Anodes for Hybrid Ni–Fe Cell Devices

Abstract

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 2 O 3 nanospheres. Only after a simple and conventional hydrothermal treatment in HNO 3 solution, nearly all of the iron rust can evolve into sphere-like α-Fe 2 O 3 products with a typical size of ∼30 nm. When serving as actives for electrochemical energy storage, the in situ generated α-Fe 2 O 3 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 2 O 3 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.

High‐Capacity Iron‐Based Anodes for Aqueous Secondary Nickel−Iron Batteries: Recent Progress and Prospects

“…Zhu et al synthesized the α-Fe 2 O 3 nanospheres with the average diameter of 30 nm as shown in Figure 5a from the iron rust wastes using a costeffective and reliable way. [55] This revolutionary strategy was relatively low-cost and controllable, and could not only avoid high energy consumption but also relieve environmental pollution problems. With the small size, the as-built α-Fe 2 O 3 nanosphere could bring more active sites for electrochemical reactions and greatly increase the specific energy density.…”

Sol-Gel Mediated Greener Synthesis of γ-Fe2O3 Nanostructures for the Selective and Sensitive Determination of Uric Acid and Dopamine

“…It can be seen that the attained results pointed out that the value of magnetization decreases regularly with the increasing concentration of AV extract. The reduction in magnetization (Ms) value of the green synthesized iron oxide nanostructures related to the bulk materials is mainly ascribed to the nano-sized particles [41]. This significant decrease in magnetization values are mainly attributed to the presence of higher amount of AV extract on the surface of γ-Fe 2 O 3 nanostructures.…”

Mesoporous Fe3O4@C nanoarrays as high-performance anode for rechargeable Ni/Fe battery

“…Among various aqueous batteries, the alkaline Ni/ Fe battery has attracted much attention because Ni and Fe are earth-abundant, ecofriendly, and rather cheap compared with other alternatives [8]. Despite these merits, the relatively low power/energy density and short cycle life of Ni/Fe battery limit their wide applications [9,10]. To improve their performance, delicate design and synthesis of nanostructured electrodes have been widely reported [11][12][13][14][15][16].…”