Applied Catalysis B: Environmental, Vol.219, 329-343, 2017
Synergistic effect in MMT-dispersed Au/TiO2 monolithic nanocatalyst for plasmon-absorption and metallic interband transitions dynamic CO2 photo-reduction to CO
Structured montmorillonite (MMT) dispersed Au/TiO2 nanocomposite has been designed and synthesized through a facile sol-gel method. Cordierite monolithic support was employed in order to load the catalyst for improved photo-activity and reusability in CO2 utilization process. The samples were characterized by XRD, Raman, SEM, TEM, FI'IR, XPS, N-2 adsorption-desorption, UV-vis and PL spectroscopy. The synergistic effect of MMT-dispersed Au/TiO2 nanocatalyst was evaluated in a gas-phase dynamic monolith photoreactor system using UV and visible light irradiations. The maximum CO yield over 0.5 wt.% Au-10 wt.% MMT-loaded TiO2 catalyst reached to 1223 p mole g-catal.(-1) h(-1), a 24 fold higher than the amount of CO produced over the 10 wt.% MMT/TiO2 and 68 times the amount of CO produced over the bare TiO2 catalyst. The other products observed with considerable amounts were CH4 and C2H6. This enactment under UV-light was due to interband transition of Au in catalyst composite. Enhanced photo-activity under simulated solar energy for CO2-to-CO reduction was due to LSPR effect of Au in the MMT/TiO2 sample. More importantly, the performance of Au-MM/TiO2 catalyst for CO evolution under UV-light was 6 folds higher than using visible light. The synergistic effect between MMT transition metals and Au ions and faster adsorption-desorption process contributed to remarkably enhance dynamic CO2 reduction to CO. The present design of catalyst provides prolonged stability to catalyst while CO evolution sustained even after 44h of operation time. The reaction mechanism developed to understand the role of Au/MMT and monolithic support on the photo-activity and reusability of catalyst for CO2 photo-reduction to fuels. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:CO2 Photo-reduction;Inter-band transition;Plasmon absorption;Synergistic effect;Montmorillonite;Monolithic support