Design and reversible hydrogen storage capacity determination of unique nanoarrays of TiO2 and carbon nanotubes

Abstract

In this project hydrogen storage studies were carried out on TiO2 nanotubular arrays of different diameters prepared by electrochemical anodization, combined with template-grown carbon nanotubes (CNTs). The growth of the CNTs on the nanotubular TiO2 arrays was accomplished by chemical vapor deposition. The hydrogen storage capacity was determined for the nanotubular TiO2 and the combined TiO2-CNT arrays, by charging and discharging hydrogen with a Sievert's apparatus. It was found that the presence of carbon nanotubes on nano-porous titanium oxide can enhance storage of hydrogen as determined by volumetric means. The hydrogen uptake in as-anodized TiO2 nanotubes was found to be 2 wt% at liquid nitrogen temperature (77 K) and 0.94 wt% at room temperature. Desorption results for TiO2 at 393 K and 300 K were 1.5 wt% and 0.7 wt%, respectively. The CNT-TiO2 composites showed a hydrogen uptake capacity of 1.94 wt% at room temperature and 2.5 wt% at 77 K. The desorption results were 1.8 wt% at 393 K and 0.68 wt% at room temperature. It was seen that the hydrogen uptake was higher at lower temperatures and discharge was increased significantly at higher temperatures for both TiO2 and CNT/TiO2 samples. The utilization of this novel hydrogen storage method can be recognized as a break-through in the hydrogen economy as applied to on-board vehicular applications.