Photocatalytic water splitting and hydrogenation of CO2 in a novel twin photoreactor with IO3-/I- shuttle redox mediator

Article abstract of DOI:10.1016/j.apcata.2015.08.027

One of the major drawbacks in photoreduction of carbon dioxide (CO₂) into hydrocarbons is the high thermodynamic barrier involved, resulting in low photoreduction quantum efficiency (PQE). A novel twin photoreactor system has been developed to enhance the PQE of CO₂ reduction as a solution to this limitation. The twin photoreactor divides the oxygen (O₂)-generating photocatalyst and the dual-function photocatalyst having both CO₂ reduction and hydrogen (H₂) production capabilities in two compartments by a membrane thus preventing the undesired reverse reaction. Herein, the dual-function photocatalyst can hydrogenate CO₂ via the produced H₂, allowing the overall reaction to be more thermodynamically favorable. The charge balance was accomplished by the aid of IO₃^-/I^- redox mediator in the twin photoreactor for shuttling electrons. Two visible-light photocatalysts, Pt/WO₃ (O₂-generating photocatalyst) and GaN:ZnO-Ni/NiO (both CO₂-reducing and H₂-generating photocatalysts) were used. We found out that through the application of the twin photoreactor system under artificial sunlight (AM1.5G 300 W Xenon lamp), the PQE was enhanced more than 4-folds in comparison with that in the single photoreactor, an increase from 0.015% to 0.070%. A possible enhancing mechanism for twin photoreactor, in compare with the conventional single photoreactor, is also proposed based on the knowledge of species present during the photocatalytic reaction.