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 °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.