HYDROGEN ADSORPTION OF NANOSTRUCTURED HYDROTALCITE BASED MIXED OXIDES ADSORBENT

The research work in this thesis focuses on the reversible hydrogen adsorption using
Mg, Ni and Al containing hydrotalcite based adsorbents. Different techniques were
applied to form the reversible intermetallic hydride from hydrotalcite based
adsorbents for enhancing hydrogen sorption capacity and to get the favorable
hydrogen adsorption thermodynamics and kinetics.
The nano-structured adsorbents have been synthesized vm the coprecipitation
method under variable pH (7-ll) and low supersaturation method. The adsorbents
were characterized to find the optimum metal composition and to determine the
physical and chemical properties such as crystallinity, surface morphology, surface
energy, metals distribution and interactions. The source material and converted mixed
oxides adsorbents phases and crystallinity were confirmed by X-ray diffraction
(XRD) technique. The specific BET surface area of synthesized adsorbents of
Mg(Ni,Al)O are in a range of 110 to 325 m2/g with narrow pore size distribution
(PSD) in a range of 5-15 nrn and pore volume of0.86-1.09 cm3/g. Inductive couple
plasma mass spectrometry (ICP-MS) analyses ensured the homogenous metals
distribution of adsorbents. Hexagonal plate-like and flower-like morphology of the
adsorbents were found through field emission scanning electron microscopy
(FESEM) and high resolution transmission electron microscopy (HRTEM) analyses
and selected area diffraction pattern (SAED) of Mg(Ni,Al)O demonstrated that the
adsorbent were poly-crystalline with the crystallite size range of 12-22 nm.
Temperature programmed reduction (TPR) analyses revealed the order of interaction
between metals and reduction temperature of different oxides phases.