Since its discovery in 2004 by Andre Geim and Konstantin Novoselov, and their subsequent award of the Nobel Prize in Physics in 2010, graphene has attracted great interest from scientists and engineers around the world [1]. This carbon-based material, renowned for its exceptional electrical conductivity, mechanical strength and versatility, is revolutionizing numerous fields, including light-emitting diodes, field-effect transistors, sensors, biomedical devices, electrochemical energy storage, solar cells, catalyst supports and thermal interface materials.
Despite its exceptional promise, graphene prepared via common top-down synthesis approaches tend to stack, which limits ion and electron transport and hinders its performance in practical applications. This challenge inspired our pursuit of a unique structure: vertical graphene nanosheets (VGSs). The morphology of VGSs is that graphene nanosheets grow perpendicular to their supporting surface. This architectural twist not only preserves native properties of graphene but overcomes the stacking bottlenecks for improving its integration into advanced devices.
Method for scalable preparation of VGSs
In our recent paper published on Nature Protocols, "Scalable growth of vertical graphene nanosheets by thermal chemical vapor deposition", we detailed a thermal chemical vapor deposition (thermal CVD) method to grow graphene vertically.
The journey toward this scalable method began over a decade ago when Prof. Jie Yu, an expert in carbon materials, was exploring carbon nanofibers (CNFs) and their potential as scaffolds for energy applications. In 2013, Prof. Jie Yu managed to grow radial graphene layers on CNFs using NH₃-assisted carbonization. The outcome was promising, but the graphene domains were too small to be functionally significant [2].
In 2018, after numerous iterations, Prof. Jie Yu's team made a breakthrough: by using thermal chemical vapor deposition (thermal CVD) with methane and hydrogen gases, which achieved catalyst- and template-free growth of full-sized vertical graphene nanosheets directly on CNFs [3]. Subsequently, VGSs were grown on carbon fibers (CFs) with micron diameters by thermal CVD for application as a catalyst support in water electrolysis in 2021 [4]. Furthermore, the team grew VGSs on Si particles through the thermal CVD method, as a lithium-ion battery anode, to effectively enhance conductivity and mitigate the issue of volume expansion [5].
As illustrated in Figure 1, VGSs were formed on these three types of substrates in the alumina ceramic crucible through the deposition action of CH4 and the etching action of H2 with the sufficient heating by the tubular furnace.
Advantages and perspectives
The VGSs produced by this protocol is high-quality (pure, dense and uniform) with good graphene layers separation. Additionally, the thermal CVD is able to grow VGSs on powder substrates (with a capacity of 5 kg per batch of powder substrates) and features much lower equipment cost, comparing to the common CVD method of plasma-enhanced chemical vapor deposition (PECVD).
The thermal CVD method reported in this protocol is scalable. The amount of substrate, the growth height of the VGSs, and the flow rates of CH4 and H2 can all be adjusted according to specific requirements. As long as the tube furnace and alumina ceramic crucible are sufficient to accommodate the samples, the amounts of substrates can be increased or decreased according to needs. The growth time of VGSs can also be adjusted according to needs; the longer the growth time, the greater the height of the VGSs. The gas flow rate parameters of CH4 and H2 can also be proportionally scaled up or down to accommodate experiments in tube furnaces of different sizes.
To date, we have successfully implemented the thermal CVD method for substrates of Si or C. The expansion of VGSs growth using thermal CVD on other substrates has not yet been fully explored, particularly on metal substrates commonly used in industry, such as Fe, Al, Zn, Ti and Cu etc. This presents a broad area for further research and development. We will continue to focus on extending the thermal CVD method to various non-metallic and metallic substrates, with the goal of accelerating the application of VGSs across a wide range of fields. We believe this effort lays the foundation for establishing VGSs as a universal platform in nanotechnology.
References
1. Dresselhaus M. S. & Paulo T. Araujo P. T. Perspectives on the 2010 Nobel Prize in Physics for graphene. ACS Nano 4, 6297-6302 (2010).
2. Zhao, L. et al. Carbon nanofibers with radially grown graphene sheets derived from electrospinning for aqueous supercapacitors with high working voltage and energy density. Nanoscale 5, 4902-4909 (2013).
3. Zeng, J. et al. 3D graphene fibers grown by thermal chemical vapor deposition. Adv. Mater. 30, 1705380 (2018).
4. Ji, X. et al. Graphene/MoS2/FeCoNi(OH)x and Graphene/MoS2/FeCoNiPx multilayer-stacked vertical nanosheets on carbon fibers for highly efficient overall water splitting. Nat. Commun. 12, 1380 (2021).
5. Yu, P. et al. Hierarchical yolk-shell silicon/carbon anode materials enhanced by vertical graphene sheets for commercial lithium-ion battery applications. Adv. Funct. Mater. 35, 2413081 (2025).