Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template

Abstract

Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports.

Confined Carbon Mediating Dehydroaromatization of Methane over Mo/ZSM‐5

“…With the aid of 13 CNMR spectroscopy,w e found that surface carbon is mainly of ap olyaromatic nature as characterized by ab road peak centered at 128 ppm (Figure 3a). [17] Furthermore,w hile the amount of carbon deposited on the catalysts during the induction period is similar, the C/Mo ratio varies from about 12 for 1%Mo to about 4f or 5%Mo, suggesting that confined carbon is not exclusively bound to Mo-species (Supporting Information, Figure S13, Table S2). We also found that the H/C ratio of surface carbon species is about 0.5, and that it remains constant during the reaction (Supporting Information, Figure S14).…”

Superaerophobic graphene nano-hills for direct hydrazine fuel cells

“…5 Moreover, these materials possess high intrinsic electrical conductivity that facilitates the electron transfer processes for hydrazine oxidation along with high surface area. 6 These striking properties have led to the use of carbon-based materials for various fuel-cell technologies, including hydrazine fuel cells. For instance, Li et al 7 showed that a complex of graphene and carbon nanotubes can be effectively utilized for the oxygen reduction reaction on the anode side of the fuel cell.…”

Chemical vapour deposition of freestanding sub-60 nm graphene gyroids

“…4,20 More recently, nano-porous zeolites decorated with Lanthanum have been used as a template to create carbon frameworks, albeit not fully graphitised. 7 Further, computational modelling has recently highlighted the potentially exceptional properties of periodic gyroid graphene structures. 13 A well-known challenge in particular for pure metal templates is their high self-diffusivity, 21 which means that metal templates with sub-100 nm unit cell sizes are prone to sintering, i.e.…”

“…Recent literature highlights the promise of such porous, foam-like materials, in particular those derived from graphene, in applications ranging from (opto)electronics, 1,2 artificial skin, 3 electrochemistry, [4][5][6] and catalysis 7 to thermal management, 8 self-cleaning, 9 sorption and filtration, 10 sensors, 11 bio-medical 12 and mechanical metamaterials. 13,14 Among the various synthetic strategies and 3D assembly approaches, 15 chemical vapour deposition (CVD) has emerged as the most viable route not only to grow highly crystalline 2D material films but also to directly grow covalently bonded, continuous 3D networks of these 2D materials.…”