A novel twin reactor for CO₂ photoreduction to mimic artificial photosynthesis

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.