Abstract

We report the effect of hydrothermal synthesis conditions on the morphological, optical and electrochemical properties of as-prepared iron oxide (γ-Fe₂O₃) and hydroxide (α-FeOOH) nanostructures. The physico-chemical identification of these Fe-based nanostructures using X-ray diffraction, scanning/transmission electron microscopy, porosity and Raman spectroscopy analyses revealed a temperature-depended phase transformation. A maghemite and goethite iron-based nanostructured formation was observed in nanorod and trigonal nanofiber shape-like morphology with mean diameters ranging from 32 to 50 nm. The textural analysis of the nanofibers confirmed mesoporosity with a specific surface area of ~ 129 m² g⁻¹ (in γ-Fe₂O₃) and 23 m² g⁻¹ (in α-FeOOH). The electrochemical performance of the iron oxide and hydroxide nanofiber electrodes with and without the addition of activated carbon (AC) was also investigated. The sample electrodes composed of γ-Fe₂O₃, γ-Fe₂O₃/AC, α-FeOOH and α-FeOOH/AC showed remarkable specific capacities of 164 mAh g⁻¹, 330 mAh g⁻¹, 51 mAh g⁻¹ and 69 mAh g⁻¹ at 1 A g⁻¹ gravimetric current. The influence of the phase transformation linked to the synthesis temperature, and the inclusion of an electric double-layer AC material into the nanofibers clearly demonstrates an enhancement in their energy-storage capability. Furthermore, the Fe-based nanofibers exhibited excellent cycling stability with good capacity retention of 73% and 99.8%, respectively, after 2000 cycles at a high 30 A g⁻¹ gravimetric current as well as low resistance obtained by impedance spectroscopy analysis. The implication of the results depicts the potential of adopting these γ-Fe₂O₃ nanorods as suitable material electrodes in electrochemical energy-storage devices.

Graphic abstract

中文翻译：

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无模板水热法合成氧化铁和氢氧化铁纳米纤维的光学和电化学性能

摘要

我们报告所制备氧化铁（γ-Fe的形态，光学和电化学性质的水热合成条件的影响₂ ö ₃）和氢氧化（α-的FeOOH）纳米结构。使用X射线衍射，扫描/透射电子显微镜，孔隙率和拉曼光谱分析对这些铁基纳米结构进行物理化学鉴定，发现了温度相关的相变。在纳米棒和三角形纳米纤维形状状形态中观察到磁赤铁矿和针铁矿的纳米结构，平均直径范围为32至50 nm。纳米纤维的纹理分析证实用〜129米的比表面积中孔² 克^-1（以γ-的Fe ₂O ₃）和23 m ²  g ^-1（在α-FeO​​OH中）。还研究了添加和不添加活性炭（AC）的氧化铁和氢氧化铁纳米纤维电极的电化学性能。构成的样品电极γ-的Fe ₂ ö ₃，γ-的Fe ₂ ö ₃ / AC，α-的FeOOH和α-的FeOOH / AC表现出显着的164比容量毫安克^-1，330毫安克^-1，51毫安克^-1和69 mAh g ^-1在1 A g ^-1重力电流。与合成温度相关的相变的影响，以及在纳米纤维中包含双电层AC材料，清楚地表明了其能量存储能力的提高。此外，在高30 A g ^-1重量电流下经过2000次循环后，铁基纳米纤维表现出出色的循环稳定性，分别具有73％和99.8％的良好容量保持率，以及通过阻抗谱分析获得的低电阻。结果的含义描述了采用这些γ-Fe的潜在₂ ö _3个纳米棒在电化学能量储存设备合适的材料的电极。

图形摘要