Type of presentation: Oral

MS-2-O-3438 3D insight on the catalytic nanostructuration of few-layer graphene

Melinte G.^{1, 2}, Janowska I.², Baaziz W.², Florea I.¹, Moldovan S.¹, Arenal R.^{3, 4}, Wisnet A.⁵, Scheu C.⁵, Begin-Colin S.¹, Begin D.², Pham-Huu C.², Ersen O.¹

¹Institut de Physique et Chimie des Matériaux de Strasbourg, CNRS-Université de Strasbourg, 23, rue du Loess, 67037 Strasbourg, France , ²Institut de Chimie et Procédés pour l’Energie, l’Environnement et la Santé, CNRS, ECPM, Université de Strasbourg, 25, rue Becquerel, 67087 Strasbourg, France, ³Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, 50018 Zaragoza, Spain, ⁴ARAID Fundation, Calle Mariano de Luna, 50018 Zaragoza, Spain, ⁵Department of Chemistry and Center for NanoScience, Ludwig Maximilians University, Butenandtstr. 11, 81377 Munich, Germany

georgian.melinte@ipcms.unistra.fr

The catalytic cutting of few-layer graphene (FLG) is attracting nowadays an increase attention due to its potential applications in both the field of catalysis and graphene nanoribbons (GNRs) fabrication.[1,2] The nanopatterning of FLG sheets with open and subsurface channels develops during a chemical reaction between the metal nanoparticles (NPs) and the carbon substrate under a hot gaseous atmosphere (H2, O2).[3,4] The use of the FLG powder in the field of catalysis is limited by the restacking process which significantly decreases its surface accessibility. By channeling the FLG sheets the restacking effect is significantly reduced. This is due to the creation of a porous network which will not only increase the surface accessibility but also will create a network of defects that will further serve as anchorage sites for the surface decoration. Moreover, the nanopatterning of FLG has the potential of creating nanosheets with well-defined shapes and edge configurations which can be transformed in single-layer GNRs by simple techniques as for instance the chemical exfoliation.
To characterize the channeling process and the obtained nanostructures we used an initial system consisting in Fe3O4 NPs dispersed on FLG sheets. The FLG/Fe3O4 composite has undergone a heating treatment in a H2 atmosphere. HR-TEM shows that the well-defined channels are not randomly oriented but follow specific crystallographic directions i.e. <11-20> and <10-10> (Figure 1), leading to the formation of two types of edge morphologies, zigzag and armchair, respectively. The electron tomography analyses reveal interesting features on both the nanopattering mechanisms and properties of the nanostructured FLG sheets. Figure 2 indicates the effect of a topographical step-up of the FLG sheet . Accordingly, one observes that after interaction the cutting direction remains unchanged but the depth of the open-surface channel is changing proportional with the height of the step-up. Figure 3 displays the impact of a step-up event with the height larger than the size of the NP. As previously, the cutting direction remains unmodified and the result is the formation of subsurface channel. When topographic step-down events are encountered by the active NPs, the particle either stops or changes the direction.
[1] Mei-xian Wang et al., J. Phys. Chem. Lett., 4, 1484−1488 (2013).
[2] Ci Lijie et al., Nano Res. 1, 116-122 (2008).
[3] Tim J. Booth et.al, Nano Lett. 11, 2689–2692 (2011).
[4] Datta S. et. al Nano Lett. 8(7), 1912-1915 (2008).

Fig. 1: HR-TEM images illustrating the preferential crystallographic orientation of the tranches with a zigzag (a) and armchair (b) edge morphology (scale bars 5 nm).	Fig. 2: a) TEM projection of a selected channel (scale bar 50 nm). b) XY slice through the reconstructed volume. c) XZ slices through the selected channel at the positions numbered in Figure 1a. d) YZ slice taken through a region indicated in Figure 1a with a yellow dotted line. Scale bars 20 nm.
Fig. 3: a) TEM projection of two subsurface channels (scale bar 50 nm). b) XY slice through the reconstructed volume (scale bar 20 nm). c) and d) YZ slices taken at the position indicated in Figure 1a with the yellow line (scale bar 20 nm).