New progress has been made in the preparation technology of resin-based three-dimensional carbon materials

Three-dimensional graphene carbon material is a new type of carbon nanomaterial composed of two-dimensional graphene at the macro scale, which has broad application prospects in the fields of energy storage and conversion, catalysis, adsorption and separation. To date, a large number of preparation methods for three-dimensional carbon materials have emerged, which can be classified as solid routes (precursors such as graphene oxide, natural and synthetic polymers, etc.) and gaseous routes (chemical deposition of gaseous carbon sources). Among them, the solid route often lacks the ability to flexibly regulate the composition and structure of the product, while the gaseous route is extremely dependent on the catalytic template and has low efficiency. The liquid state is a special state between solid and gas, which combines the molecular bulk density of solid state and the flow and compatibility of gas. The development and exploration of liquid routes is considered to be the key to achieving efficient and controllable structure and properties of three-dimensional graphene materials. For a long time, researchers have made a lot of efforts and attempts to establish a synthetic route of liquid three-dimensional graphene materials, but no substantial progress has been made.

Xiaoqing Liu, a researcher from the new thermosetting resin team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, based on years of research experience in bio-based thermosetting resins (Composites Part B, 2020, 190, 107926; Green Chemistry, 2021, 23, 8643; Progress in Polymer Science, 2021, 113,101353; Chemical Engineering Journal 2022, 428,131226; Composites Science and Technology, 2022, 219, 109248), proposed that the essence of the development of bio-based materials is to achieve efficient use of biochar. Based on this, the team used laser ablation to convert bio-based thermosetting resin into functional carbon materials (Carbon, 2020, 163, 85; Carbon, 2021, 183, 600; ACS Nano, 2021, 15, 12, 19490; Nano Energy, 2022, 100, 107477;Small, 2022, 2202960), plans to complete the closed-loop conversion from “biochar” to “bio-based resin” to “functional carbon”.

Recently, based on a rich research base in these two interdisciplinary fields, the team successfully achieved direct conversion from liquid precursors to three-dimensional graphene materials by designing the molecular structure of carbon precursors and using laser etching (as shown in Figure 1). This new preparation route combines the advantages of laser manufacturing and liquid precursors. Almost all the macrostructure of graphene that is widely used can be directly prepared by this liquid route, including powder, porous membrane, functional coating, flexible Janus structure, and macroscopic three-dimensional graphene material with customized structure, showing great research value and application prospects.

Figure 1 Direct synthesis of laser-induced graphene materials from liquid precursors

In addition, the functional components of the prepared three-dimensional graphene materials are also highly controllable. Thanks to the good compatibility of liquids, functional organic or inorganic fillers can be directly mixed into liquid precursors and formed in situ graphene-based composites under laser irradiation, including heteroatom doping, metal nanoparticle doping, metal oxide nanoparticle doping, and other functional components doped (Figure 2). For example, high-entropy alloy-doped graphene materials can be obtained by blending a variety of metal-organic compounds with liquids and laser irradiation. Among them, the high-entropy alloy is uniformly distributed on the porous skeleton surface of three-dimensional graphene in the form of nanoparticles, and its particle size and content can be flexibly adjusted by the doping ratio of the precursor.

Fig. 2 Preparation and characterization of three-dimensional graphene functional composites

It is worth mentioning that a new 3D printing principle (Selective Laser Transforming, SLT, as shown in Figure 3) is also proposed in the paper, that is, the three-dimensional structure of graphene materials is customized through the layer-by-layer conversion of liquid precursors, which makes an important expansion of the current extremely limited carbon material 3D printing technology. Due to the non-melt, insoluble and non-polymerization, the development of 3D printing technology suitable for carbon materials has long been regarded as a great challenge. Compared with the existing printing strategy, in addition to the fundamental difference in principle, the biggest advantage of this in-situ printing method through the in-situ growth of the surface unit is the simple and efficient printing process and the high structural continuity of the printed product. The SLT printing process not only avoids the preparation of traditional energy-consuming and high-pollution graphene oxide, but also eliminates the need for additional high-temperature annealing reduction process for the printed product. The conductivity and strength of the printed products reached 4380 S/m and 4.4 Mpa, respectively, which were significantly better than the traditional 3D printing graphene materials.

Figure 3 New SLT graphene 3D printing technology

The results were published online in Advanced Materials, a top journal in the field of materials under the title “Direct Conversion of Liquid Organic Precursor into 3D Laser-induced Graphene Materials”. This work was supported by the National Natural Science Foundation of China (52003282, U1909220), Zhejiang Outstanding Youth Fund (LR20E030001) and Zhejiang Leading Innovation Team Project (2021R01005). (Source: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences)

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