Hydrogen Storage in Porous Single-Walled Carbon Nanohorns Dispersed with Pd-Ni Alloy Nanoparticles

Single-walled carbon nanohorns containing Pd-Ni alloy nanoparticles (Pd-Ni/SWCNHs) were prepared by the gas-injected arc-in-water method, and high-pressure H-2 absorption by these nanoparticles was investigated using a magnetic suspension balance at 30 degrees C and 1.2 MPa. The amount of H-2 absorbed by them was larger than the predicted combined absorption contributed by Pd-Ni alloy and pure-carbon SWCNHs. This synergetic H-2 absorption was induced by the combination of Pd-Ni alloy nanoparticles and SWCNHs and occurred because of a spillover effect. Remarkably, H-2 absorption occurred by diffusing into as-grown Pd-Ni/SWCNHs. Opening the pores of Pd-Ni/SWCNHs by a mild oxidation treatment drastically improved the H-2 absorption. Consequently, the diffusivity of H-2 into Pd-Ni/SWCNHs was enhanced to the point where H-2 absorption could reach saturation in an extremely short time.