Effect of ionic liquid in a pressurized reactor to enhance CO2 photocatalytic reduction at TiO2 modified by gold nanoparticles

This work describes the synergic effect of gold nanoparticles as co-catalyst on TiO2 nanotubes (TNT/AuNP) in aqueous medium containing the ionic liquid (IL) 1-Butyl-3-methylimidazolium tetrafluorobo-rate, in a pressurized photocatalytic reactor, as a good strategy to enhance CO2 conversion into value-added products. The surface plasmon resonance of the gold NPs improve the photoexcitation under vis-ible light and slightly change the TNT band gap from 3.2 to 2.9 eV. Methanol production using TNT/AuNP in aqueous medium containing 2% (v/v) BMIM-BF4, 1 g L-1 Na2SO3 as a hole scavenger, under 5 atm pressure and solar irradiation, produce up to 279.6 mM (mmol L-1) of methanol and 98.8 mM of methane, with the quantum yield of 1.12% at 440 nm. Isotope-labeled studies by GC/MS proved that (CO2)-C-13 is the source for photoproduction of (CH3OH)-C-13. The results indicate that the combination of the Au co-catalyst size, high pressure, and IL can provide efficient modulation of CO2 conversion. (C) 2021 Elsevier Inc. All rights reserved.