One-step synthesis of single-walled carbon nanohorns dispersed with Pd-Ni alloy nanoparticles by gas-injected arc-in-water method and effects of synthesis factors on their hydrogen sensor sensitivity

Abstract

Single-walled carbon nanohorns (SWCNHs) dispersed with Pd-Ni alloy nanoparticles were synthesized in a technique requiring a single step by a gas-injected arc-in-water method using Pd-Ni-C mixed powders charged in an anode hole. It was found that the Ni/Pd weight ratio in the alloy nanoparticles dispersed in the products uniquely depended on the initial Ni/Pd weight ratio; Pd in the products was enriched by a factor of two when the Ni/Pd weight ratio in the initial mixture was higher than 0.1, while Ni was enriched at a Ni/Pd weight ratio below this threshold. The average diameter of alloy nanoparticles increased with the initial weight of the metallic components, while the average diameter of the discrete forms of the SWCNH aggregates exhibited the opposite tendency. Increasing the amount of the metallic compounds in the initial mixed powders caused the enrichment of Pd. The effect of adding Pd-Ni alloy nanoparticles into the products on the carbonaceous structures of SWCNHs was not detected by Raman analysis. The sensitivities of H2 sensors using the SWCNHs dispersed with Ni, Pd, and Pd-Ni alloy nanoparticles were compared, and the sensitivity of the sensor using the Pd-Ni alloy was the highest.