Electrochemical hydrogen storage behavior of single-walled carbon nanotubes (SWCNTs) coated with Ni nanoparticles

The electrochemical hydrogen storage properties of Ni nanoparticle coated SWCNT electrodes were investigated. A surface modification technique enabled different amounts of Ni nanoparticles to be deposited on the SWCNT surface, which was first chemically oxidized by 6 N HNO3. The characteristic properties of the SWCNT samples coated with 4–12 wt.%Ni nanoparticles were examined using a scanning electron microscope with energy dispersive spectroscopy (SEM/EDX); micro-Raman spectroscopy; thermal analysis techniques consisting of both thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and Brunauer–Emmett–Teller (BET) measurements. It was found that all of the SWCNT samples coated with 4–12 wt.%Ni nanoparticles possessed a similar pore-size distribution. According to the electrochemical test results, the highest electrochemical discharge capacity of 1404 mA h g−1 was obtained for the SWCNT electrode coated with 8 wt.%Ni nanoparticles, which corresponded to 5.27 wt.% hydrogen storage. This enhancement of electrochemical hydrogen storage capacity was ascribed to the fact that the Ni nanoparticles act as a redox site, thus leading to an improved electrochemical hydrogen storage capacity. The results indicated that the SWCNT coated with Ni nanoparticles are a potential material for hydrogen storage.