Oxidation-Reduction Processes for Graphene and Graphene Oxide Production

Graphene oxide is known as an intermediate product for the creation of graphene, based on oxidation-reduction processes. As a product featuring excellent chemical, physical and optical properties, graphene oxide has its own value too.

The number of oxygen groups within the sheets and the edges can be controlled depending on how the production process is operated, affecting band gaps and conductivity.

Graphene oxide can be altered and chemically linked to polymers with appropriate bonding groups as it is rich in oxygen-containing functional groups such as carboxyl, hydroxyl and epoxy.

This results in higher mechanical properties such as abrasion resistance. The polymer containing graphene oxide also has superior flame-retardant and anti-bacterial properties in some embodiments.

Graphene oxides can also be employed to optimize catalytic activity in instances where a high content of oxygen groups and a high surface area are required. A lot of research is currently ongoing in this area.

The Sixth Element has gained a world leading position in manufacturing graphene oxide and low concentrated graphene oxide suspensions as a result of its modified, proprietary Hummer’s technique. A mono-layer graphene oxide is available directly after the oxidation and exfoliation process of graphite.

Further processing steps then result in either highly concentrated graphene oxide suspensions, in which the layers are stacked to graphite oxide, or low concentrated, almost purely mono-layer graphene oxide suspensions.

Currently, there are two varieties of very stable, low concentrated graphene oxide suspensions available. In order to avoid restacking of the mono-layers and achieve high suspension stability, the concentrations are limited to 1%.

In the lateral size of the primary particles, the types differentiate. The D50 of the primary particle size of SE3122 is 8 µm, while SE3522 is made up of primary particles with a D50 of below 4 µm. The production of 450 t per annum on ready-to-use graphene oxide suspension is enabled using Current equipment.

Due to the large adsorption capacity and high adsorption speed, such suspension can be utilized as adsorbents in water treatment plants to remove heavy metals. The heavy metals can be regained environmentally friendly by using further processing steps. This is currently undergoing long-term testing by The Sixth Element’s customers.

Trials have demonstrated that the addition of graphene suspensions of The Sixth Element in oil drilling operations enhances the quality of the filter and results in a reduction of fluid loss. When graphene oxide is added to the drilling fluid, the filter cake is formed. The resulting filter cake is denser, leading to better stabilization of the well wall.

Another benefit is that water cannot enter the oil reservoir. The addition of graphene oxide nanoparticles reduces the viscosity of the heavy oil during its recovery, resulting in a higher yield of the heavy oil. This mechanism is currently studied on a large scale.

The graphene oxide suspension with the trade name SE2430W is highly concentrated and has been utilized for a number of years as a precursor for graphene-based heat dissipation films, which are widely utilized in mobile phones. SE2430W-N is marketed outside the heat dissipation application.

In a further development step, The Sixth Element can now produce halogen-free graphene oxide materials on a large scale. Particle size can be altered using ultrasonic equipment extremely easily, as with other graphene oxide materials from The Sixth Element.

Appearance (left),1 wt% water suspension (middle) and dilute water solution (right) of SE2430W-N.

Appearance (left),1 wt% water suspension (middle) and dilute water solution (right) of SE2430W-N. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.

Special process modification of the oxidation-reduction process has allowed The Sixth Element to produce an extremely high electrically conductive type of graphene called SE1234.

SEM 1234.

SEM 1234. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.

SE1234 has a higher mono-layer rate than other graphene types created using an oxidation-reduction process. It is available as a powder and can be dispersed into coatings and polymers with appropriate methods. 

Much less SE1234 is required to achieve the same electrical conductivity in the application in comparison to SE1233, an already good electrically conductive graphene type. Sample quantities of SE1234 are available from August 2021.

Surface resistance (O) by adding SE1234 into acrylic resin with the weight of 0%, 0.8% and 1.575 %. The coating substrate is PET and the thickness of the film should be 0.5mm (wet state before drying).

Surface resistance (Ω) by adding SE1234 into acrylic resin with the weight of 0%, 0.8% and 1.575%. The coating substrate is PET and the thickness of the film should be 0.5 mm (wet state before drying). Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.

Where a low addition of conductive additive in polymer formulation is needed, SE1234 can be utilized. It can also be added to lithium-ion battery cathode material to enhance its electronic conductivity and increase cyclic life and specific capacity. It is currently being tested by The Sixth Element’s joint venture ShanYuan.

This information has been sourced, reviewed and adapted from materials provided by The Sixth Element (Changzhou) Materials Technology Co.,Ltd.

For more information on this source, please visit The Sixth Element (Changzhou) Materials Technology Co.,Ltd.

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