Guillaume Muller

A sustainable aqueous route to highly stable suspensions of monodispersed nano ruthenia

Highly stable suspensions of monodispersed ruthenia nanoparticles have been prepared via a sustainable aqueous oxidative pathway. The nanoparticles (2 nm) have been thoroughly characterized by TEM, XRD, XPS, MS-TGA and thermodiffraction. The addition of hydrogen peroxide in the RuCl3 solution provokes a fast oxidation of Ru(III) ions into Ru(IV). This increases the rate of the hydrolysis/condensation reactions and further promotes the nucleation over the growth of the particles. The very high stability conditions of the colloidal suspension have been studied. This aqueous one-step process, which uses no organic solvent or toxic pollutant additive, is quick and produces calibrated ruthenia nanoparticles in high yields. It presents a green alternative to the preparation and use of ruthenia. As examples, two applications are presented. In the first, RuO2 coatings have been tested for their electrical capacitance. In the second, RuO2/TiO2 catalysts, prepared from the controlled deposition of ruthenia nanoparticles on TiO2 particles, have been proven to be highly effective for the production of methane from CO2.

Discussion on a percolating conducting network of a composite thin-film electrode (≤1 μm) for micro-solid oxide fuel cell application.

Ni/Gd0.1Ce0.9O(2-δ) (Ni/GDC) and La0.6Sr0.4Fe0.8Co0.2O(3-δ)/Gd0.1Ce0.9O(2-δ) (LSCF/GDC) porous thin-film electrodes with thicknesses between 120 and 500 nm were synthesized through templated sol-gel chemistry coupled with the dip-coating process and heat treatment. The thin films consist of two interpenetrated networks made of pores and inorganic materials. The porous structure was composed of multi-scale pores with dimensions ranging from macro- to nanosize and with an oriented columnar structure. The dimension of the percolation network is discussed as a function of the chemical nature of the percolating components and the particle/thickness ratio. A three-dimensional percolation network is achieved in the LSCF/GDC composite, while a two-dimensional percolation network is observed for the Ni/GDC composite. This difference is related to the microstructure of the composite thin film. An anisotropic columnar structure is observed for Ni/GDC, while an isotropic structure is achieved for LSCF/GDC.