A novel twin reactor for CO2 photoreduction to mimic artificial photosynthesis

[Display omitted] ► We demonstrated the photo CO2 hydrogenation by a novel twin reactor to mimic photosynthesis. ► A twin reactor can separate H2 and O2 to prevent the backward oxidation reaction. ► The dual photocatalyst system was more efficient than single photocatalyst system under simulated sunlight AM1.5G. One of the best routes to covert CO2 into energy and simultaneously reduce atmospheric CO2 is photosynthesis. In natural photosynthesis, the first step is water splitting in which proton is generated and O2 is released using solar energy. The second step is the Calvin cycle in which CO2 is reduced to hydrocarbons. This study demonstrated the photocatalytic hydrogenation of CO2 by using a novel twin reactor to mimic photosynthesis process in nature. The twin reactor, which divided H2-generating photocatalyst and O2-generating photocatalyst in two compartments using a membrane, first achieved separate H2 and O2 evolution to prevent the backward reaction to form water under visible light irradiation. The generated hydrogen was then used to perform CO2 hydrogenation by CO2 reduction photocatalyst. The advantage is that CO2 hydrogenation is a spontaneous reaction based on the thermodynamics. The single photocatalyst system using Pt/CuAlGaO4 as both H2-generating photocatalyst and CO2 reduction photocatalyst, was compared with the dual photocatalyst system using Pt/SrTiO3:Rh and Pt/CuAlGaO4 as H2-generating photocatalyst and CO2 reduction photocatalyst, respectively, under simulated sunlight AM1.5G. The dual photocatalyst system has demonstrated photoreduction quantum efficiency (PQE) of 0.0051%, which is more than doubled the PQE of the single photocatalyst system.