Deposition of Ni nanoparticles onto porous supports using supercritical CO2: effect of the precursor and reduction methodology

The deposition of Ni nanoparticles into porous supports is very important in catalysis. In this paper, we explore the use of supercritical CO2 (scCO2) as a green solvent to deposit Ni nanoparticles on mesoporous SiO2 SBA-15 and a carbon xerogel. The good transport properties of scCO2 allowed the efficient penetration of metal precursors dissolved in scCO2 within the pores of the support without damaging its structure. Nickel hexafluoroacetylacetonate hydrate, nickel acetylacetonate, bis(cyclopentadienyl)nickel, Ni(NO3)2 · 6H2O and NiCl2 · 6H2O were tried as precursors. Different methodologies were used: impregnation in scCO2 and reduction in H2/N2 at 400°C and low pressure, reactive deposition using H2 at 200–250°C in scCO2 and reactive deposition using ethanol at 150–200°C in scCO2. The effect of precursor and methodology on the nickel particle size and the material homogeneity (on the different substrates) was analysed. This technology offers many opportunities in the preparation of metal-nanostructured materials.