Synergistic effect in MMT-dispersed Au/TiO2 monolithic nanocatalyst for plasmon-absorption and metallic interband transitions dynamic CO2 photo-reduction to CO

Abstract

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, FTIR, XPS, N2 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 μ 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 44 h 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.