Evolution of Useless Iron Rust into Uniform α‑Fe<sub>2</sub>O<sub>3</sub> Nanospheres: A Smart Way to Make Sustainable
Anodes for Hybrid Ni–Fe Cell Devices
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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<sub>2</sub>O<sub>3</sub> nanospheres. Only after a simple and conventional
hydrothermal treatment in HNO<sub>3</sub> solution, nearly all of
the iron rust can evolve into sphere-like α-Fe<sub>2</sub>O<sub>3</sub> products with a typical size of ∼30 nm. When serving
as actives for electrochemical energy storage, the <i>in situ</i> generated α-Fe<sub>2</sub>O<sub>3</sub> 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>2</sub>O<sub>3</sub> 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