Graphene and other two-dimensional atomic crystals

* Explorations on new two-dimensional atomic crystals

* CVD growth of high-quality graphene and their macrostructures

* Chemical methods for large-scale production of graphene

* Graphene for lithium ion batteries and supercapacitors

* Graphene for flexible optoelectronics and energy storage devices

* Graphene for thermal management, functional coatings and composites, etc.

Using chemical vapor deposition (CVD) method, we have synthesized a three-dimensional flexible and conductive interconnected graphene network with metal foams as templates (Fig. 1) and realized the repeated growth of millimeter-size single-crystal graphene on Pt (Fig. 2). Moreover, we have proposed a novel bubbling method to transfer graphene from metals to arbitrary substrates, which is nondestructive not only to graphene, but also to the metals. Aiming at the large-scale applications of graphene, we have developed a new synthesis method and realized the mass production of high-quality graphene at a low cost.

In the aspect of properties and applications of graphene, we have revealed the excellent field emission property of graphene and the synergistic energy storage effect between graphene and oxide electrode materials, and expanded their applications in flexible energy storage devices. In addition, we have fabricated a series of graphene-based functional materials and devices including elastic conductors, highly sensitive gas sensors, highly efficient thermal management materials, lightweight electromagnetic interference shielding materials, and flexible lithium ion batteries with ultrafast charge and discharge rate, etc.

In addition to graphene studies, we have developed a floating catalyst CVD method to prepare double-walled carbon nanotubes, and systematically studied their structures, Raman spectra and growth mechanism. We have also developed a metal-catalyst-free CVD process for the high-efficiency growth of single-walled carbon nanotubes and revealed their vapor-solid-solid growth mechanism.

Fig 1. (a), (b) Three-dimensional interconnected graphene network, and (c) the elastic conductor made by graphene network/PDMS composite.

Fig 2. (a)-(c) SEM images of millimeter-size hexagonal single-crystal graphene grains grown on Pt, and (b'), (c') Optical images of the graphene grains in (b) and (c) transferred onto Si/SiO₂ by the bubbling transfer method.