Development and Up-Scaling of Electrochemical Production and Mild Thermal Reduction of Graphene Oxide

Abstract

To reduce the global emissions of CO2, the aviation industry largely relies on new light weight materials, which require multifunctional coatings. Graphene and its derivatives are particularly promising for combining light weight applications with functional coatings. Although they have proven to have outstanding properties, graphene and its precursor graphene oxide (GO) remain far from application at the industrial scale since a comprehensive protocol for mass production is still lacking. In this work, we develop and systematically describe a sustainable up-scaling process for the production of GO based on a three-step electrochemical exfoliation method. Surface characterization techniques (XRD, XPS and Raman) allow the understanding of the fast exfoliation rates obtained, and of high conductivities that are up to four orders of magnitude higher compared to GO produced via the commonly used modified Hummers method. Furthermore, we show that a newly developed mild thermal reduction at 250 °C is sufficient to increase conductivity by another order of magnitude, while limiting energy requirements. The proposed GO powder protocol suggests an up-scaling linear relation between the amount of educt surface and volume of electrolyte. This may support the mass production of GO-based coatings for the aviation industry, and address challenges such as low weight, fire, de-icing and lightning strike protection.

Lightning Strike Protection: Current Challenges and Future Possibilities

“…To enhance the graphene oxide conductivity, reduction of the oxidic groups is necessary to restore the aromatic network. Various possible reduction routes such as chemical [ 46 , 47 ], thermal [ 48 ], solvothermal [ 49 ], and photoinduced [ 50 ] reduction are reported in the literature, with the first two being the most prominent. For example, powder conductivity of HI-reduced GO was measured at 2.11 × S/m, whereas thermally reduced GO achieved conductivity up to 2.41 × S/m (see Figure 5 a) [ 48 ].…”

“…Various possible reduction routes such as chemical [ 46 , 47 ], thermal [ 48 ], solvothermal [ 49 ], and photoinduced [ 50 ] reduction are reported in the literature, with the first two being the most prominent. For example, powder conductivity of HI-reduced GO was measured at 2.11 × S/m, whereas thermally reduced GO achieved conductivity up to 2.41 × S/m (see Figure 5 a) [ 48 ]. L-Ascorbic acid is a green and cheap alternative reductant showing similar capability to more toxic agents such as hydrazine or hydroiodic acid, producing reduced graphene oxide (rGO) powders with conductivity of 1.52 × S/m.…”

“…Moreover, further improvement in 2DM research will need to pay attention to the environmental impact of the chemistry in use. In this sense, green chemicals are essential for industries to comply with the goals set in the European Green Deal, as discussed in our previous work [ 48 ].…”

Recent advances in density functional theory approach for optoelectronics properties of graphene

“…Moreover, graphene-based coatings with distinct electronic properties might use electricity to generate thermal energy and transport it to the external surface, or they could improve conductivity and electromagnetic shielding to guard against lightning strikes. Therefore, optimization of the DFT and ML-DFT frameworks in future studies to modify graphene's structural and electronic properties is critical for the design and large-scale manufacturing of these graphene-based devices [ 388 , 389 ].…”

l-Ascorbic Acid Treatment of Electrochemical Graphene Nanosheets: Reduction Optimization and Application for De-Icing, Water Uptake Prevention, and Corrosion Resistance

“…This provides good upscale potential, avoids the use of toxic chemicals (e.g., manganese traces being considered harmful according to the literature), and leads to less oxidation due to milder process parameters. Yet, it bears the disadvantage of providing a distribution of multiple layer numbers following exfoliation errors. − Similar to GO, the presence of oxygen functional groups resulting from a prior exfoliation process enables material’s chemical modification with the trade-off of disturbing the aromatic backbone, which impedes both electrical and thermal conductivities of the material.…”