Enhancement of hydrogen storage capacity of multi-walled carbon nanotubes with palladium doping prepared through supercritical CO2 deposition method

Pd doped Multi-Walled Carbon Nanotubes were prepared via supercritical carbon dioxide deposition method in order to enhance the hydrogen uptake capacity of carbon nanotubes at ambient conditions. A new bipyridyl precursor that enables reduction at moderate conditions was used during preparation of the sample. Both XRD analyses and TEM images confirmed that average Pd nanoparticle size distribution was around 10 nm. Hydrogen adsorption and desorption experiments at room temperature with very low pressures (0–0.133 bar) were conducted together with temperature programmed desorption (TPD) and reduction (TPR) experiments on undoped and doped materials to understand the complete hydrogen uptake profile of the materials. TPD experiments showed that Pd nanoparticles increased the hydrogen desorption activity at moderate temperatures around at 38 °C while for undoped materials it was determined around at 600 °C. Moreover, a drastic enhancement of hydrogen storage was recorded from 44 µmol/g sample for undoped material to 737 µmol/g sample for doped material through adsorption/desorption isotherms at room temperature. This enhancement, also verified by TPR, was attributed to spillover effect. © 2017 Hydrogen Energy Publications LLCBIDEB 2211-EThe authors acknowledge Prof. Dr. Ramazan Esen from Ç.U. Physics Department for XRD measurements, Deniz Kaya for TPD-TPR measurements of Pd/MW-CNT and Atalay Çalışan for BET measurements from Chemical Engineering Department of M.E.T.U. Dr. Fatma Ulusal's financial support was provided by International Research Fellowship Programme (for PhD students) TUBITAK BIDEB 2211-E