Sharif Digital Repository

Nanostructured MgH2-Ni/Nb2O5 nanocomposite was synthesized by high-energy mechanical alloying. The effect of MgH2 structure, i.e. crystallite size and lattice strain, and the presence of 0.5 mol% Ni and Nb2O5 on the hydrogen-desorption kinetics was investigated. It is shown that the dehydrogenation temperature of MgH2 decreases from 426 °C to 327 °C after 4 h mechanical alloying. Here, the average crystallite size and accumulated lattice strain are 20 nm and 0.9%, respectively. Further improvement in the hydrogen desorption is attained in the presence of Ni and Nb2O5, i.e. the dehydrogenation temperature of MgH2/Ni and MgH2/Nb2O5 is measured to be 230 °C and 220 °C, respectively. Meanwhile,... 

The high charge carrier recombination rate and weak oxygen evolution kinetics have impeded the efficiency of WO3 photoelectrodes for water splitting. We present a novel type II heterojunction semiconductor based on mixed WS2 and MoS2 nanosheets on WO3 nanoflakes hydrothermally grown on highly porous W skeletons. The chemically exfoliated transition metal dichalcogenide (TMD) sheets with submicrometric lateral sizes were deposited on the surface of WO3 nanoflakes by the electrophoretic technique to fabricate a staggered gap heterojunction. The photoanode exhibited an impressive current density of 14.9 mA cm−2 at 1.23 VRHE which comprised ∼1.7 mA cm−2 photocurrent under 100 mW cm−2 simulated... 

A novel microspherical adsorbent for the removal of uranium from aqueous solutions was developed by immobilizing of natural bentonite in the polymeric matrix of calcium alginate. Different uptake properties of the prepared microspheres were examined using batch, stirred and column methods. The adsorbent showed high affinity toward uranium ions, especially at pHs above 3. Major uptake mechanisms included ion exchange, chelating of the (UO2)2+ ions to the -OH groups of alginate, and surface complexation with bentonite. Surprisingly, the capacity of microspheres was higher than both its constituents, revealing that a synergetic effect occurs. Adsorption kinetics was controlled by slow chemical...