Transition Metal Oxides on Reduced Graphene Oxide Nanocomposites: Evaluation of Physicochemical Properties (original) (raw)
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Modelling, Measurement and Control B
Hematite/reduced graphene oxide (Fe2O3/rGO) nanocomposite was successfully fabricated via a facile solvothermal reaction of iron precursor solution and GO leading to simultaneous deposition of iron oxide nanoparticles and in situ reduction of GO without any reducing agent. Texture and morphology, microstructure, chemical and surface composition of the nanocomposite were investigated by scanning electron microscopy, Xray diffraction, Raman spectroscopy, thermo-gravimetric analysis and X-ray photoelectron spectroscopy, respectively. Its electrochemical performance as anode material for sodium ion batteries was preliminarily evaluated via galvanostatic cycling. The results prove that the Fe2O3 nanoparticles are uniformly anchored onto the surface of graphene nanosheets and that the Fe2O3/rGO nanocomposite shows interestingly higher specific capacities compared to the bare Fe2O3.
The Journal of Physical Chemistry C, 2017
Graphenothermal reduction mechanism of Fe2O3 by graphene oxide (GO) is elucidated through careful experimental analysis. The degree of oxidation (DO) of GO plays a key role in controlling the reduction of Fe2O3 by GO. GO with low DO follows a conventional three stage reaction path i.e., ′2 + 2 3 → / 3 4 () → / () → / ()′ (where EG is exfoliated reduced graphene oxide) at temperatures 650 and 750 °C to reduce Fe2O3. Whereas the GO with higher DO transforms rapidly and ceases the reduction at Stage I i.e., with the formation of EG/Fe3O4 at 650 °C. It is also found that slow thermal treatment of GO continues the reduction to Stage II and further to Stage III depending on time of heating and temperature. EG/Fe3O4 (synthesized at 550 °C-5 h) by using GO with low DO showed superior cycling performance as an anode of Li-ion battery than its counterpart prepared (at 650 °C-5 h) from GO with high DO owing to good contacts between EG and
Electrochimica Acta, 2015
Fe 2 O 3-reduced graphene oxide (RGO) composites were successfully fabricated via a facile microwaveassisted reduction of graphite oxide in Fe 2 O 3 precursor solution using a microwave system, and investigated as anode material for sodium ion batteries (SIBs). Their morphologies, structures and electrochemical performance were characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy, respectively. The results show that the RGO addition can enhance the electrochemical performance of Fe 2 O 3-RGO composites. Fe 2 O 3-RGO composite with 30 wt.% RGO exhibits a maximum reversible capacity of 289 mA h g À1 at a current density of 50 mA g À1 after 50 cycles and excellent rate performance due to the synergistic effect between Fe 2 O 3 and RGO. The high capacity, good rate capability and excellent cycle performance of Fe 2 O 3-RGO composites enable them a potential electrode material for SIBs.
Reduced graphene oxide as a stable and high-capacity cathode material for Na-ion batteries
We report the feasibility of using reduced graphene oxide (RGO) as a cost-effective and high performance cathode material for sodium-ion batteries (SIBs). Graphene oxide is synthesized by a modified Hummers' method and reduced using a solid-state microwave irradiation method. The RGO electrode delivers an exceptionally stable discharge capacity of 240 mAh g −1 with a stable long cycling up to 1000 cycles. A discharge capacity of 134 mAh g −1 is obtained at a high current density of 600 mA g −1 , and the electrode recovers a capacity of 230 mAh g −1 when the current density is reset to 15 mA g −1 after deep cycling, thus demonstrating the excellent stability of the electrode with sodium de/intercalation. The successful use of the RGO electrode demonstrated in this study is expected to facilitate the emergence of low-cost and sustainable carbon-based materials for SIB cathode applications. The development of advanced energy storage systems has become an important research area because of their vast usage in applications ranging from portable electronic devices to grid-level energy storage. Intermittent energy sources such as geothermal, solar, and wind require large-scale energy storage systems 1. Lithium-ion batteries (LIBs) are dominant amongst the energy storage technologies for small-to medium-scale electronic devices. The use of electrical energy storage is expanding to large-scale applications, such as transportation and stationary storage systems. However, LIBs are not suitable for large-scale applications because of their high production cost and limited lithium resources. Sodium-ion batteries (SIBs) have emerged as a potential candidate for large-scale energy storage systems (ESS) because of their advantages of a low production cost and evenly distributed global sodium reserves compared to lithium 2–5. For the successful application of SIBs, the electrodes should deliver high round-trip efficiency, a long cycle life and flexible power. In recent years, several cathode materials such as layered oxides (NaMO 2 (M = 3d transition metals) and their solid solutions) 6–10 , sulfates (e.(CN) 6 ·H 2 O and KMFe(CN) 6 where M = transition metal, Na 2 Mn[Mn(CN) 6 ]) 21–23 , have been reported for SIBs. However, most of these materials either have a low sodium storage capacity (< 200 mAh g −1) or undergo rapid capacity degradation over cycling. The composition of most of the cathodes used in SIBs include transition metals, which are not environmentally benign and are often costly. Furthermore, the difficult synthesis procedure, low electronic conductivity and complex structural arrangements during sodium de/intercalation process make layered transition metal oxides unsuitable for use in high-performance SIBs at their present stage of development 24,25. In that regard, inexpensive, environmentally friendly and highly conductive carbonaceous materials are of great interest as electrode materials for electrochemical energy storage devices such as SIBs, LIBs and superca-pacitors 26–28. Among them, graphene, due to its ultrathin two-dimensional structure, has unique properties such as high electrical conductivity, large surface area, and high chemical and mechanical stabilities, and has been used widely in various applications such as electrodes for energy storage systems, field effect transistors, sensors , and catalyst support 29–32. Graphene has been extensively investigated for its use in electrochemical energy
In the present study, we report the synthesis of Fe@Ag nanoparticles/2-aminoethanethiol functionalized reduced graphene oxide (rGO) composite (Fe@AuNPs-AETrGO) and its application as an improved anode material for lithium-ion batteries (LIBs). The structure of the Fe@AgNPs-AETrGO composite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray pho-toelectron spectroscopy (XPS). The electrochemical performance was investigated at different charge/discharge current rates by using CR2032 coin-type cells and cyclic voltammetry (CV). It was found that the spherical Fe@AuNPs were highly dispersed on the rGO sheets. Moreover, the Fe@AuNPs-AETrGO composite showed high specific gravimetric capacity of about 1500 mAh g −1 and long-term cycle stability.
Journal of Alloys and Compounds, 2019
A novel nanocomposite electrode material consisting of Fe 2 O 3 and reduced graphene oxide (RGO/Fe 2 O 3) has been synthesized using a cost-effective chemical approach for its application in the field of energy storage devices. The morphological and structural characterizations of the as-synthesized RGO/Fe 2 O 3 nanocomposite materials were done using scanning electron microscopy (SEM) and X-ray diffraction respectively. The electrochemical properties of the RGO/Fe 2 O 3 nanocomposite were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The RGO5/Fe 2 O 3 nanocomposite exhibited higher specific capacitance (50 Fg-1) at a scan rate of 0.1 V/s in 0.5 M H2SO4 solution than the pristine RGO. Moreover, the impedance spectroscopy showed that the value of charge transfer resistance (RCT) was 91.1 and 21.64 ohm for RGO1/Fe 2 O 3 and RGO5/Fe 2 O 3 respectively, indicating a decrease in the charge transfer resistance and increased charge conductivity for RGO5/Fe 2 O 3. This low-cost protocol provides an alternative pathway for the large-scale production of various composite materials with controllable dimensions for energy storage and conversions.