Graphene oxide as a promising photocatalyst for CO2 to methanol conversion (original) (raw)
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Electric and Photocatalytic Properties of Graphene Oxide Depending on the Degree of Its Reduction
Nanomaterials
When graphene oxide is reduced, the functional groups are released and the structure becomes more ordered. The degree of reduction might be tunable with the process parameters. In our work, graphene oxide is prepared and the effect of thermal and chemical reduction is investigated. The samples are characterized with TG/DTA-MS, SEM-EDX, TEM, XPS, ATR-FTIR, Raman spectroscopy and XRD. Their electrical resistance, cyclic voltammetry and photocatalytic activity data are investigated. The conductivity can be varied by several orders of magnitude, offering a tool to match its electrical properties to certain applications. Low temperature reduction in air offers a material with the highest capacitance, which might be used in supercapacitors. The bare graphene oxide has considerably larger photocatalytic activity than P25 TiO2. Reduction decreases the activity, meaning that reduced graphene oxide can be used as an electron sink in composite photocatalysts, but does not contribute to the pho...
Graphene Oxide as An Efficient Photocatalyst For Photocatalytic Reduction of CO2 Into Solar Fuel
INTERNATIONAL JOURNAL OF AUTOMOTIVE AND MECHANICAL ENGINEERING
Photocatalytic reduction of CO2 into solar fuel such as methane and methanol, is an attractive approach to simultaneously solve the energy crisis and global warming problem. Herein, comparative photocatalytic activity of graphene oxide nanosheets have been investigated for photocatalytic reduction of CO2 into methane and methanol in continuous gas and liquid phase photoreactor system. The graphene oxide sheets were prepared according to Tour's method. The chemical composition and optical properties was evaluated through XPS and UV-vis spectroscopy. Graphene oxide nanosheets exhibited maximum amount of 224.87 μmol/g.h methanol and 14.8 μmol/g.h methane in liquid and gas phase system, respectively. Higher yield of methanol in liquid phase compared to methane in gaseous system can be attributed to dispersion of graphene oxide sheets in water. Hence, graphene oxide nanosheets are efficient photocatalyst for CO2 reduction into methanol. Nevertheless, further research is essential to improve the photostability of graphene oxide sheets for real application of photocatalytic CO2 reduction.
Photochemical stability and reactivity of graphene oxide
Journal of Materials Science, 2015
The photoreactivity of graphene oxide (GO) suspensions was investigated with a double aim: i) to give insights into the previously reported photo-reduction process, which allows a partial elimination of the oxygen-containing groups from the 2D graphitic structure; ii) to explore the possible use of GO as photo-activator able to promote the photo-transformation/abatement of organic molecules. To reach these goals and clarify some peculiar aspects of the photochemistry of GO till now obscure or confuse, we synthesized and characterized stable GO suspensions which were then subjected to UV-Vis irradiation for prolonged times. GO underwent partial photoreduction with the release of gaseous molecules and soluble organic species (e.g. carboxylic acid). The mechanisms of photo-reduction occurring under air or N 2 are different, as assessed by the release in solution of diverse soluble molecules. In the presence of oxygen, at long irradiation time, a complete solubilization of the graphenic structures was observed. No difference in the nature and amount of released gases (principally CO 2 and CO) was observed in the oxic or anoxic conditions. The possible use of GO as photo-activator was evaluated by using phenol as probe molecule. GO revealed a double role of photo-activator and reagent in phenol degradation, as competition was assessed between GO self-transformation/reduction and phenol degradation. At prolonged irradiation time a marked reactivity of the photoformed species was observed and the complete degradation was achieved for both organic small molecules formed from GO and the phenol added as probe molecule.
Effect of Dissolved Oxygen Content on Photocatalytic Performance of Graphene Oxide
arXiv: Materials Science, 2018
Graphene, a two-dimensional (2D) promising emergent photocatalyst consisting of earth-abundant elements. This study evaluated the potential of graphene oxide (GO) towards photocatalytic degradation of a novel organic dye, Methylene Blue (MB). In this work, photocatalytic activity of graphene oxide (GO), graphene oxide (GO) along with hydrogen peroxide (H2O2) were tested by photodegrading Methylene Blue (MB) in aqueous solution. The resulted GO nanoparticles were characterized by X-ray powder diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Fourier Transform Infrared Ray Spectroscopy. The XRD data confirms the sharp peak centered at 2Theta=10.44 degree corresponding to (002) reflection of GO. Based on our results, it was found that the resulted GO nanoparticles along with H2O2 achieved ~92% photodecolorization of MB compared to ~63% for H2O2 under natural sunlight irradiation at pH~7 in 60 min. The influences of oxygen and hydrogen peroxide (H2O2) on the ...
Graphene oxide (GO) was synthesized by a modified Hummer's method. 1,2 1 g of graphite flakes (Sigma-Aldrich) was grounded with 20 g of NaCl (Himedia) in a mortar pastel for 30 minutes. The excess NaCl was washed by rinsing repeatedly with water through vacuum-filtration. The above washed graphite flakes were dried in oven for 30 minutes at 70 0 C. 23 ml of 36N H 2 SO 4 (Rankem) was added to the dried graphite flakes in a 250 ml round bottom flask and stirred for 24 hours at room temperature. Then the temperature was raised to 40 0 C and 100 mg of NaNO 3 (Himedia) was dissolved in the solution. This step is followed by slow addition of 500 mg of KMnO 4 (Himedia) into the reaction mixture, keeping the reaction temperature below 45 0 C. Subsequently, 3 ml of water was added to the flask, followed by another 3 ml after 5 minutes. After next 5 minutes, 40 ml of water was added slowly to it. After 15 minutes the flask was removed from the oil bath and 140 ml of H 2 O and 10 ml of 30% H 2 O 2 were added. Then the flask with the reaction mixture was stirred at room temperature for 10 minutes. Then reaction mixtures were washed by centrifugation with 5% HCl and then further with excess of water. The final precipitate was dispersed in 100 ml of water and ultrasonicated for 30 minutes. Graphite particles in the dispersion were separated by centrifugation at 5000 rpm for 5 minutes and a brown homogeneous supernatant was collected. Then pure GO was collected from the above supernatant solution by centrifugation at 15000 rpm for 30 minutes and re-dispersed in 100 ml of ethanol (~2 mg/ml).
Graphene oxide as a photocatalytic material
Applied Physics Letters, 2011
Surface enhanced Raman scattering and localized surface plasmon resonance of nanoscale ultrathin films prepared by atomic layer deposition Appl. Phys. Lett. 101, 023112 Work function measurements on nano-crystalline zinc oxide surfaces J. Appl. Phys. 111, 123710 (2012) Iron oxide nanoparticles fabricated by electric explosion of wire: focus on magnetic nanofluids AIP Advances 2, 022154 Ambipolar charge injection and transport of few-layer topological insulator Bi2Te3 and Bi2Se3 nanoplates
Electrochemical reduction of NAD+ on graphene oxide and chemically reduced graphene oxide nanosheets
Materials Science and Engineering: B, 2020
In this work, the electrochemical reduction of nicotinamide adenine dinucleotide (NAD +) was studied on graphene oxide (GO) and chemically reduced graphene oxide (CRGO) nanosheets. GO was prepared by modified Hummer's method and reduced using hydrazine hydrate to obtain CRGO. The material was characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The TEM studies reveal the presence of nanosheets and the XRD exhibited the characteristic pattern of GO and CRGO respectively. The Raman spectrum showed a slight red shift for CRGO compared to GO. The electrochemical reduction of NAD + was investigated on bare and modified glassy carbon electrode (GCE) using various electrochemical techniques such as linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The reduction of NAD + to NADH occurs at a relatively lower potential of −1.04 V on GO/GCE compared to CRGO/GCE (−1.08 V) and bare GCE (−1.12 V). GO/GCE showed enhanced catalytic activity due to the presence of defect structures and oxygen functional groups on the carbon framework. The kinetic studies further revealed that reduction is an adsorption controlled process. From LSV obtained at different scan rates the number of electrons transferred was deduced as 1.7 and 1.2 for GO/GCE and CRGO/GCE respectively and the values are correlated with other electrochemical techniques such as hydrodynamic voltammetry and DPV. The heterogeneous rate constant determined from hydrodynamic voltammetry showed that GO/GCE (8.5 × 10 −5 cm s −1) exhibited higher rate constant than CRGO/GCE (7.4 × 10 −7 cm s −1). EIS was carried out at different cathodic potentials to analyze the kinetics at the electrode-electrolyte interface. The detection of NAD + was performed on GO/GCE using DPV which showed a linear range of 100-1100 µM with a LOD of 19.36 µM. It was found that GO/GCE showed good catalytic activity compared to CRGO/GCE with better electron transfer kinetics.
Chemical Engineering Journal, 2017
A series of TiO 2 /nitrogen (N) doped reduced graphene oxide (TiO 2 /NrGO) nanocomposites with varying concentration and bonding configurations of nitrogen were synthesized by a one-step urea-assisted hydrothermal method, and applied to photoreduction of CO 2 with H 2 O vapor in the gas-phase under the irradiation of a Xe lamp. The effect of the N dopant (doping quantity and bonding configuration) on the catalytic performance of TiO 2 /NrGO was examined. In particular, TiO 2 /NrGO-300, with a 300:1 mass ratio of urea/GO in precursor solution, had the highest CO production yield (356.5 μmole g-1), manifesting a significant 4.4 and 2.2-fold enhancements of CO yield over pure TiO 2 and TiO 2 /rGO, respectively. More significantly, TiO 2 /NrGO showed excellent catalytic stability during the prolonged reaction, while catalytic deactivation was observed for both pristine TiO 2 and TiO 2 /rGO after a few hours. The promoting effects of N dopants on the structure and activity of TiO 2 /NrGO were investigated. It was demonstrated that NrGO with an appropriate N quantity and N-bonding configuration acted as a dual-functional promoter, simultaneously enhancing CO 2 adsorption on the catalyst surface and facilitating electron-hole separation, while eventually boosted the photocatalytic performance. Experimental results in this work provide a better understanding of the critical roles of N dopants in the synthesized composites and also inspire the ongoing interest in better design of other N-doped graphene based materials for photoreduction of CO 2 .
Graphene-Semiconductor Hybrid Photocatalysts and Their Application in Solar Fuel Production
Advanced 2D Materials , 2016
Harvesting solar light by semiconductors for conversion of carbon dioxide (CO 2) and water into fuel is a revolutionary approach for fulfilling energy appetite and mitigating increased greenhouse gases concentration in our environment. Nanocomposite materials synthesized by hybridization of semiconductors with graphenic materials owing to their better absorbance, charge separation, and higher surface area have been proved to be superior candidates for photocata-lytic applications from quantum efficiency and selectivity viewpoints. This chapter is focused on the discussion of various graphene/semiconductor nanocomposite systems for enhanced photocatalytic performance for water splitting as well as CO 2 reduction. So far, extensive work has been carried out on TiO 2 and non-TiO 2 semiconductors, but still quantum efficiency is far from the real-life application and limited to 5-50 μmol. Recent developments in this realm suggested that gra-phene oxide (GO) or reduced GO boosted the performance of semiconductors by facilitating charge separation. Furthermore, functionalization of these hybrids with dyes and metal complexes provided a significant enhancement in the product yield.