Thermal effects on hydrogen storage capacity of Pd/MWCNT nanoparticles deposited at moderate pressure and temperature supercritical carbon dioxide conditions

Abstract

Pd nanoparticles were deposited on MWCNT support for the first time at 80 ℃ and under 2500 psi scCO2 conditions via a bipyridyl precursor in the absence co-solvent. After deposition, the samples were heated under different atmospheres. Then their morphological and hydrogen uptake capacities were investigated. An average particle size between 7−9 nm was estimated via HR-TEM images while intense Pd(111) and Pd(200) sites were detected for all heated samples except no thermally treated one which exhibits PdHx sites. The highest hydrogen adsorption at room temperature was recorded for the samples heated under oxygen. At room temperature, Pd loading amount was found to be effective in means of captured hydrogen. Hence, at higher temperatures, hydrogen uptake of samples treated under nitrogen atmosphere was higher. Additionally, in case of the sample which was not thermally treated, a signal referring to hydrogen release between 200−300 °C during reduction was detected.