Electric and Photocatalytic Properties of Graphene Oxide Depending on the Degree of Its Reduction (original) (raw)
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Solar Energy, 2019
Abstract In this study, TiO2 nanoparticles (NPs) /reduced graphene oxide (RGO) composites were prepared by hydrothermal process and physiochemical, optical, photocatalytic and photoelectrochemical properties of prepared materials was investigated. Photocatalytic activity measurement showed that methylene blue (MB) photodegraded faster by TiO2-RGO composites compared to bare TiO2. Furthermore, photoelectrochemical (PEC) properties of TiO2 and TiO2-RGO electrodes were investigated under the illumination of a 150 W Xe lamp in 1M aqueous solution of KOH as the electrolyte. Moreover, TiO2-RGO electrodes showed greatly improved photocurrent density which is 3.3-fold higher than pure TiO2. Combined analyses of Mott-Schottky plots and electrochemical impedance spectroscopy (EIS) confirmed that RGO in the TiO2-RGO nanocomposite increased the donor concentration (ND), decreased recombination process of charge carriers (τD), thinner the space charge layer (WSCL) and reduced flat band potential (VFb) of the TiO2, thereby greatly enhancing the PEC performances of the TiO2 photoanodes. The improved PEC performance of the TiO2-RGO nanocomposite compared to TiO2 NPs attributed to great enhancement of electron transport through the RGO in the TiO2- RGO film and consequently charge separation.
Nanoscale, 2013
Efficient reduction of graphene oxide (GO) by chemical, thermal, electrochemical, and photo-irradiation techniques has been reviewed. Particular emphasis has been directed towards the proposed reduction mechanisms of GO by different reducing agents and techniques. The advantages of using different kinds of reducing agents on the basis of their availability, cost-effectiveness, toxicity, and easy product isolation processes have also been studied extensively. We provide a detailed description of the improvement in physiochemical properties of reduced GO (RGO) compared to pure GO. For example, the electrical conductivity and electrochemical performance of electrochemically obtained RGO are much better than those of chemically or thermally RGO materials. We provide examples of how RGO has been used as supercapacitor electrode materials. Specific capacitance of GO increases after reduction and the value has been reported to be 100-300 F g À1 . We conclude by proposing new environmentally friendly types of reducing agents that can efficiently remove oxygen functionalities from the surface of GO.
The Journal of Physical Chemistry C, 2011
Solution-phase photocatalytic reduction of graphene oxide (GO) to reduced graphene oxide (RGO) by titanium dioxide (TiO 2 ) nanoparticles produces an RGO-TiO 2 composite that possesses enhanced charge transport properties beyond those of pure TiO 2 nanoparticle films. These composite films exhibit electron lifetimes up to four times longer than that of intrinsic TiO 2 films due to RGO acting as a highly conducting intra-particle charge transport network within the film. The intrinsic UV-active charge generation (photocurrent) of pure TiO 2 was enhanced by a factor of ten by incorporating RGO; we attribute this to both the highly conductive nature of the RGO and to improved charge collection facilitated by the intimate contact between RGO and the TiO 2 -uniquely afforded by the solutionphase photocatalytic reduction method. Integrating RGO into nanoparticle films using this technique should improve the performance of photovoltaic devices that utilize nanoparticle films, such as dye sensitized and quantum-dot sensitized solar cells.
Characteristic of Thermally Reduced Graphene Oxide as Supercapacitors Electrode Materials
IOP Conference Series: Materials Science and Engineering
We investigated graphene like material named reduced graphene oxide (RGO) as an electrode material by employed graphene oxide (GO). Thin film of GO was prepared on the indium thin oxide (ITO) substrate by spin-coating method using varied concentration of GO that dispersed in water. In order to remove its oxygen contained, GO film was thermally reduced at 200 0 C for 1 hour. We used cyclic voltammetry to measure its CV characteristic and estimated its specific capacitance. We obtained the highest specific capacitance of 6.53 mF g −1 that measured from 4 mg ml-1 RGO thin film at scan rate 25 mVs-1 .
Photo catalytic reduction of oxygenated graphene dispersions for supercapacitor applications
Reduced graphene oxide (rGO) obtained from aqueous graphene oxide (GO) tends to agglomerate with time and hinders the commercial scale applications for high-density energy storage. Here, we report a photo-catalytic reduction of GO dispersions in N-Methyl- 2-Pyrrolidone (NMP) under deep UV light (λ ~ 253 nm) for 60 min. The obtained hydrophobic rGO dispersions are electrochemically stable for more than 160 d and exhibit a high Brunauer–Emmet–Teller (BET) surface area of ~260 m2 g−1. The NMP being a dipolar aprotic solvent serves as an electron donor and its high dipole moment enhances the electrochemical stability of rGO. Furthermore, the fabricated supercapacitor exhibits a high specific capacitance, charge retention, energy and power density of ~220 F g−1 (current density of 0.5 A g−1), up to 1000 charging/discharging cycles, 7.32 Wh kg−1 and 130 W kg−1, respectively. The high stability of dispersion and electrochemical performance of synthesized rGO is envisaged for potential applications in high density energy storage and conductive inks for flexible electronics.
Catalysts
In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO2 nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO2 led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradati...
Modification of graphene oxide with titanium dioxide by alcoholic reduction
Fullerenes, Nanotubes and Carbon Nanostructures, 2018
Graphene oxide (GO) nanocomposites doped with DEGUSSA (P25) was synthetized by (GO) alcoholic reduction at high temperatures, during the reduction the P25 anchored to the spaces left by carbonyls groups in the graphene network, this incorporation improved photocatalytic behavior by retarding the electro-hole pair (e ¡ h C). Raman spectroscopy confirms the anchorage, because the material with higher load of TiO 2 presented a band at 1100 cm ¡1 belonging to Carbonate's groups (CO 3) and a total modification of the bands D and G, also this material presents a band gap of 2.54 eV. The P25 incorporation into graphene three-dimensional arrangement is notorious in diffraction x ray patterns, because the graphene diffraction pattern shows a sharpened and smaller peak than the starting graphene oxide. The incorporation of TiO 2 to graphene sheets, improved the band gap, which P25 being of 3.2 eV was reduced to almost 2.5 eV, naturally this allows it, to be an excellent material to be used as photoanodes, photovoltaic devices and photocatalysis, the latter case, its demonstrated by a photodegradation of methylene blue at 60 ppm exposed to solar light and 25 ppm exposed to a sodium lamp that emits radiation close to 589 nm.
Synthesis and evaluation of reduced graphene oxide for supercapacitor application
Materials Today: Proceedings, 2020
The paper reports synthesis of graphene oxide (GO) using modified Hummer's method and its hydrothermal assisted reduction to produce reduced graphene oxide (rGO) for supercapacitor applications. Synthesized GO and rGO were characterized using Raman spectroscopy and their I d /I g ratio was found to be 0.94 and 0.87, respectively. Scanning Electron Microscopy (SEM) was also performed on samples for detailed surface morphology information. UV-Vis spectroscopy was employed to investigate optical properties. FT-IR spectroscopy was utilized to get the information of attached functional groups and electrochemical characterization (cyclic voltammetry) was used to test the charging discharging behavior of the material. The specific capacitance of synthesized rGO was found to be 105F/g.
Characterization of graphene oxide reduced through chemical and biological processes
Journal of Physics: Conference Series, 2013
The study of new materials for transparent electrodes or new heterojunctions made of 2D materials combinations is a very active research topic. Challenges to overcome are the modulation of the optoelectronic properties of such materials to achieve competitive photovoltaic devices. In this work, graphene oxide was reduced into graphene through different chemical (hydrazine, ultraviolet photocatalysis) and biological (microorganisms) processes. We benchmarked the reduction efficiency by probing materials characteristics using various physical characterization techniques. X-ray photoelectron spectroscopy (XPS) analyses were carried out to observe the effectiveness of the reduction processes through the sp 2 /sp 3 content. In addition, the homogeneity of the reduction is investigated on micrometer scale sample with micro Raman mapping and extraction of the I D /I G ratio. Conductive-probe atomic force microscopy (CP-AFM) was employed to investigate the longitudinal conductivity of the different samples. The results show that hydrazine based reduction remains the most efficient. However, the bacterial procedure demonstrated partial reconstruction of the carbon network and reduced the amount of oxygenated functional groups.
Chemically Reduced Graphene Oxide as Electrodes for Energy Storage Applications
The International Conference on Electrical Engineering
Supercapacitors have attracted increasing attention due to their widespread applications, such as hybrid electric vehicles, power tools, portable electronic equipment and other devices. Using larger surface area of graphene electrodes and thinner dielectrics to achieve larger capacitances is a new trend for increasing capacitance of supercapacitors. This allows for energy densities greater than those of conventional capacitors and power densities greater than those of batteries.. In this paper, graphene oxide was synthesized by improved Hummers method. polyaniline PANI/grapheneoxide (GO) nanocomposite electrode materials were prepared from aniline (ANI), GO and ammoniumpersulfate (APS) by insitu chemical polymerization in ice bath. GO in composite was reduced for 5h and 20h. The crystal structure and the surface topography of all materials were characterized by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The electrochemical properties were evaluated by cyclic voltammetry (CV), charge-discharge measurements, electrical impedance spectroscopy (EIS) and a four-point probe, respectively. The results show that with increasing reduction time, the oxygen content on the surface of GO was decreased, leading to increased ID/IG ratio in the Raman spectra of GO and increased conductivity of composite. Consequently, the capacitance properties of RGO/PANI composites could be significantly improved by the reduction of GO for 20h. The GO /PANI composite reduced for 20h had a specific capacitance as high as 1405.68 F/g at scan rate of 1 mV/s compared with 291.73 F/g for pristine graphene film.