Effects of different palladium content loading on the hydrogen storage capacity of double-walled carbon nanotubes

The effects of different amounts palladium loading on the hydrogen sorption characteristics of double-walled carbon nanotubes (DWCNTs) have been investigated. The physical properties of the pristine DWCNTs and Pd/DWCNTs were systematically characterized by X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller surface area measurements. Pd nanoparticles were loaded on DWCNT surfaces for the dissociation of H2 into atomic hydrogen, which spills over to the defect sites on the DWCNTs. When we use different Pd content, the particle size and dispersion will be different, which affects the hydrogen storage capacity of the DWCNTs. In this work, the hydrogen storage capacities were measured at ambient temperature and found to be 1.7, 1.85, 3.0, and 2.0 wt% for pristine DWCNTS, 1.0 wt%Pd/DWCNTs, 2.0 wt%Pd/DWCNTs, and 3.0 wt%Pd/DWCNTs, respectively. We found that the hydrogen storage capacity can be enhanced by loading with Pd nanoparticles and selecting a suitable content. Furthermore, the sorption can be attributed to the chemical reaction between the atomic hydrogen and the dangling bonds of the DWCNTs.

► Different content Pd was loaded on DWCNTs. And their hydrogen adsorption capacity has been significantly enhanced.
► The loading of Pd on the DWCNTs is believed to promote the dissociation of H2 molecules into hydrogen atoms.
► Higher dispersion and smaller particle of the Pd lead to the maximum amount of contact between the carbon and hydrogen atoms.