A 3D insight on the catalytic nanostructuration of few-layer graphene

The catalytic cutting of few-layer graphene is nowadays a hot topic in materials research due to its potential applications in the catalysis field and the graphene nanoribbons fabrication. We show here a 3D analysis of the nanostructuration of few-layer graphene by iron-based nanoparticles under hydrogen flow. The nanoparticles located at the edges or attached to the steps on the FLG sheets create trenches and tunnels with orientations, lengths and morphologies defined by the crystallography and the topography of the carbon substrate. The cross-sectional analysis of the 3D volumes highlights the role of the active nanoparticle identity on the trench size and shape, with emphasis on the topographical stability of the basal planes within the resulting trenches and channels, no matter the obstacle encountered. The actual study gives a deep insight on the impact of nanoparticles morphology and support topography on the 3D character of nanostructures built up by catalytic cutting

A 3D insight on the catalytic nanostructuration of few-layer graphene

The catalytic cutting of few-layer graphene is nowadays a hot topic in materials research due to its potential applications in the catalysis field and the graphene nanoribbons fabrication. We show here a 3D analysis of the nanostructuration of few-layer graphene by iron-based nanoparticles under hydrogen flow. The nanoparticles located at the edges or attached to the steps on the FLG sheets create trenches and tunnels with orientations, lengths and morphologies defined by the crystallography and the topography of the carbon substrate. The cross-sectional analysis of the 3D volumes highlights the role of the active nanoparticle identity on the trench size and shape, with emphasis on the topographical stability of the basal planes within the resulting trenches and channels, no matter the obstacle encountered. The actual study gives a deep insight on the impact of nanoparticles morphology and support topography on the 3D character of nanostructures built up by catalytic cutting

Hyperbranched Quasi-1D TiO2 Nanostructure for Hybrid Organic-Inorganic Solar Cells

The performance of hybrid solar cells is strongly affected by the device morphology. In this work we demonstrate a Poly(3-hexylthiophene-2,5-diyl)/TiO2 hybrid solar cell where the TiO2 photoanode comprises an array of tree-like hyperbranched quasi-1D nanostructures self-assembled from the gas phase. This advanced architecture enables us to increase the power conversion efficiency to over 1%, doubling the efficiency with respect to state of the art devices employing standard mesoporous titania photoanodes. This improvement is attributed to several peculiar features of this array of nanostructures: high interfacial area; increased optical density thanks to the enhanced light scattering; and enhanced crystallization of Poly(3-hexylthiophene-2,5-diyl) inside the quasi-1D nanostructure

Selective CO ₂ methanation on Ru/TiO ₂ catalysts: unravelling the decisive role of the TiO ₂ support crystal structure

International audienceThe catalytic hydrogenation of CO2 is a relevant strategy for mitigating CO2 emissions and its applicability relies on our ability to prepare catalysts that are highly active under mild conditions. Understanding and improving these tailored catalysts requires innovative materials synthesis routes and advanced methods of characterization. In this study, mono-dispersed 2 nm RuO2 nanoparticles were prepared as a stable colloidal suspension and deposited onto different titania supports by impregnation. Supported RuO2 nanoparticles are homogeneously dispersed at the surface of the titania supports. Then, upon annealing and reduction, metallic Ru nanoparticles are obtained, which are active in the hydrogenation of CO2 to CH4. However, depending on the crystal structure of the different TiO2 supports (anatase, rutile, and a mixture of both), the catalysts exhibited drastically diverse catalytic performances. An array of characterization tools (N2-physisorption, H2-chemisorption, HR-TEM, STEM-HAADF, 3D tomographic analysis, XRD, and XPS) was used to unravel the origin of this support effect. It appeared that catalytic behaviour was related to profound morphological changes occurring during the annealing step. In particular, advanced electron microscopy techniques allow visualisation of the consequences of RuO2 nanoparticle mobility onto titania. It is shown that RuO2 sinters heavily on anatase TiO2, but spreads and forms epitaxial layers onto rutile TiO2. On anatase, large Ru chunks are finally obtained. On rutile, the formation of a particular “rutile-TiO2/RuO2/rutile-TiO2 sandwich structure” is demonstrated. These phenomena – along with the relative thermal instability of the supports – explain why the catalysts based on the commercial P25 titania support outperform those based on pure crystalline titania. The study opens new perspectives for the design of highly active CO2 methanation catalysts