Sunlight Powered Continuous Flow Reverse Water Gas Shift Process Using a Plasmonic Au/TiO₂ Nanocatalyst

The continuous flow reverse water gas shift (rWGS) process was efficiently catalyzed by a plasmonic Au/TiO₂ nanocatalyst using sunlight as sole and sustainable energy source. The influence of the catalyst bed thickness on the CO production rate was studied, and three different catalytic regimes were identified as direct plasmon catalysis (DPC), shielded plasmon catalysis (SPC) and unused plasmon catalysis (UPC). The CO₂  : H₂ ratio was optimized to 4 : 1 and a maximum CO production rate of 7420 mmol ⋅ m^-2  ⋅ h^-1 was achieved under mild reaction conditions (p=3.5 bar, no external heating, E_e =14.0 kW ⋅ m^-2 ), corresponding to an aparent quantum efficiency of 4.15%. The stability of the Au/TiO₂ catalyst was studied for 110 h continuous operation, maintaining more than 82% of the initial CO production rate. On/off experiments mimicking discontinuous sunlight powered processing furthermore showed that the Au/TiO₂ catalyst was stable for 8 consecutive runs.