Ni/MMT-promoted TiO2 nanocatalyst for dynamic photocatalytic H2 and hydrocarbons production from ethanol-water mixture under UV-light

Photocatalytic H-2 evolution from ethanol-water mixture over Ni and montmorillonite (MMT)-loaded TiO2 nanocomposite has been investigated. The samples, prepared by a single step sol-gel method, were characterized by XRD, SEM, TEM, FTIR, XPS, UV-Vis and PL spectroscopy. The TiO2 crystal growth was controlled by Ni/MMT, thus produced anatase phase TiO2. The nickel presented over the TiO2 as Ni2+, thus promoted charges separation. The photocatalytic H-2 production activity was conducted in a gas phase continuous flow photoreactor system under UV-light. A significant enhancement in photoactivity of Ni-promoted MMT/TiO2 catalyst was detected for selective H-2 production with appreciable amounts of C-1-C-3 hydrocarbons. The highest amount of H-2 evolved over 3 wt% Ni-10 wt% MMT/TiO2 composite was 3470 mu mole g-cat.(-1)h(-1) at selectivity 99%, 2.62 order of magnitude higher than pure Ni/TiO2, 6.48 fold more than MMT/TiO2 and 6.45 times the amount of H-2 produced the over the pure TiO2 catalyst. Among the hydrocarbons, MMT promoted CH4/C2H6 production, while Ni/MMT was favorable for CH4/C3H6 production. The activity and selectivity of Ni-MMT/TiO2 was reduced at higher catalyst loading due to mass transfer limitations. In addition, significantly improved and stable cyclic performance was detected over the irradiation time for dynamic and selective H-2 evolution. The enhanced performance of the Ni-MMT/TiO2 composite for H-2 production is mainly associated with efficient charges separation due to synergistic effect of Ni/MMT and appropriate redox potentials. The reaction mechanism to understand the production of H-2 and hydrocarbons in a gas phase system is critically deliberated. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.