Electrochemically oxidised graphite (original) (raw)
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Journal of Membrane Science, 2013
Three different graphite powders with different particles sizes were tested to synthesize tubular monochannel carbon supports for micro and ultrafiltration membranes using a new process. Carbon graphite powders and organic additives were mixed with an ethanolic solution of Resol s type phenolic resin. The extruded tubes were firstly consolidated by curing the resin at 150 1C then carbonized under nitrogen stream (1 mL min −1 ) for graphitization and pores opening.
A study of oxidation of graphite electrode material before and after impregnation with salts
Carbon, 1982
Oxidative consumption of graphite electrodes in technological use can be slowed down by impregnating the electrodes with inorganic salts. Burn-off kinetics was studied for impregnated and unimpregnated electrode material at temperatures in the range 550-750°C. The dependence on specimen size and on pore volume were separated out experimentally. The evolution of pore system during oxidation is discussed. Growth of pores with radii of 200-600 nm is the main result of burn-off.
Electrochemical Modification of Graphite Surface
2017
Thermodynamic and electrochemical parameters of intercalation and deintercalation of hydrosulfate ions into the graphite substrate have been investigated using electrodes after preliminary intercalation and without this stage and involving methods of the cyclic voltammetry, electronic microscopy and general principles of the irreversible thermodynamics. Potentials of the intercalation and deintercalation starting points, potentials of the anodic and cathodic maximums have been determined and changes in the free Gibbs energy for the intercalation and deintercalation processes, changes in the enthalpy and enthropy of these processes, diffusion and migration fluxes of the hydrosulfate ions were calculated using the experimental data. Criteria of Schtakelberg, Tomesh and Shevchik and measurements of an amount of electricity required for the processes were used to evaluate the reversibility ratio of intercalation and deintercalation. It was found that raise in the intercalation-deinterca...
2017
The scheme and the reactor for the continuous electrochemical oxidation of dispersed natural graphite with a capacity of 10 kg/h are created. The operating modes providing the steady quality of oxidized graphite for the production of the functional materials from thermally exfoliated graphite (TEG) are reported. The method of obtaining the intercalated graphite and the device for its implementation adaptable to industrial manufacturing that is based on the fabrication of sealing materials and products from TEG for the equipment used in nuclear and chemical industries, power engineering, metallurgy etc. are considered.
Carbon, 2006
This pH-potentiometric study explores the factors influencing the surface charge developed in aqueous dispersions of graphite oxide (GO) after a series of oxidation treatments. Surface charging curves demonstrate that lamellar surfaces of GO are negatively charged in the entire pH range studied. While these curves were found to be independent from the concentration of the GO suspensions, they were greatly affected by the solution conditions: increasing the pH and the ionic strength promotes the dissociation of acidic surface sites as weaker functional groups progressively participate in the ion exchange process, and the electrolyte provides an effective shielding for the surface charge. Surface densities of dissociated functional groups were determined by the proton binding isotherms and the specific surface areas of GO samples. BET surface areas provided irrationally high values for site densities, while surface areas calculated by geometrical considerations gave acceptable site densities. Formation of more and more oxygen-containing groups upon the subsequent oxidation steps, detected by IR spectroscopy and elemental analysis, resulted in the enhanced acidity of graphite oxide.
Scientific reports, 2016
Graphite is a typical electrocatalyst support in alkaline energy conversion and storage devices such as fuel cells, supercapacitores and lithium ion batteries. The electrochemical behaviour of a graphite electrode in 0.5 M NaOH was studied to elucidate its surface structure/electrochemical activity relationship. Graphite voltammograms are characterized by an anodic shoulder AI and a cathodic peak CI in addition to the oxygen reduction reaction plateaus, PI and PII. AI and CI were attributed to oxidation and reduction of some graphite surface function groups, respectively. Rotating ring disk electrode (RRDE) study revealed two different oxygen types assigned as inner and outer oxygen. The inner oxygen was reduced via the more efficient 4-electron pathway. The outer oxygen reduction proceeded with a lower efficient 2-electron pathway. The calculated percentages of the 4-electron pathway were ranged from 70% to 90%. A full mechanism for the graphite surface function groups changes over...
Nano Materials Science, 2019
Electrochemistry has emerged as a major route for graphene and graphene oxide synthesis from graphite. Anodic graphite oxidation is commonly used with dilute mineral acid or aqueous salt electrolytes. In this system, the electrolyte acid concentration appears to be a critical parameter. However, the effect of the acid concentration, particularly at low concentrations, is still not fully understood. To address this issue, we used a packed bed electrochemical reactor to synthesize seven different electrochemical graphite oxide (EGO) products in 2-16 M sulfuric acid. Detailed XRD, XPS, Raman, conductivity and optical microscopy analysis of the products was carried out. We found dilute acid (<10 M) graphite oxides were less crystalline and less oxidized than those produced in stronger acids. The oxygen evolution reaction at the graphite surface appears to affect the structural changes, oxidation mechanism, and electrochemical corrosion of the anode. EGO conductivity is also strongly affected by the electrolyte's acidity. We show that well oxidized, yet reasonably conductive, single layer graphene oxide can be produced from 7.1 M acid. These results broaden our understanding of graphite electrochemistry and will serve to inform future electrochemical graphene synthesis efforts.
Reactivities of Modified and Unmodified Exfoliated Graphite Electrodes in Selected Redox Systems
2012
The electrochemical profiles of exfoliated graphite electrodes (EG) and glassy carbon electrodes (GCE) were recorded using cyclic voltammetry and square wave voltammetry in the presence of various supporting electrolytes and Fe(CN)(6)](3-/4-), Ru(NH3)(6)](2+/3+), ferrocene redox probes. In the supporting electrolytes (KCl, H2SO4, NaOH, tetrabutylammoniumtetraflouroborate, phosphate buffers), the potential windows of EG were found in some cases to be about 200 mV larger than that of GCE. The electroactive surface area of EG was estimated to be 19.5 % larger than the GCE which resulted in higher peak currents on the EG electrode. Furthermore, EG was modified with various nanomaterials such as poly (propylene imine) dendrimer, gold nanoparticles, and dendrimer-gold nanoparticles composite. The morphologies of the modified electrodes were studied using scanning electron microscopy and their electrochemical reactivities in the three redox probes were investigated. The current and the rev...