Carbon aerogel supported nickel nanoparticles and nanorods using supercritical deposition

Carbon aerogel (CA)–nickel nanocomposites were synthesized by impregnating the CAs with nickel(II) acetylacetonate (Ni(acac)2) from supercritical carbon dioxide at 30 MPa and 60 °C followed by thermal or chemical treatment using H2 at atmospheric pressure. The CA–Ni(acac)2–CO2 adsorption isotherm was measured at the impregnation condition and found to be linear. The decomposition of Ni(acac)2 on the CA surface was investigated using thermo-gravimetry and mass-spectroscopy. Propane was found in the gaseous decomposition products. CA–Ni composites were characterized using Infrared (IR) Spectroscopy and characteristic Ni(acac)2 peaks were found to disappear after thermal or chemical treatments. X-ray diffraction (XRD) data confirmed that after H2 treatments nickel nanocrystals were present in the CA. Transmission electron microscopy (TEM) revealed the presence of nickel nanostructures dispersed homogeneously on the surface of the CA. In the samples treated with H2 at 170 °C, the average Ni nanoparticle size increased from 4.9 to 12.9 nm when the Ni loading increased from 3 to 6.5 wt.%. The H2 treatment at 200 °C resulted in Ni nanorods with diameters of 7–11 nm and lengths of 25–50 nm dispersed throughout the CA surface.