Heterogeneous photocatalytic performances of CO₂ reduction based on the [Emim]BF₄ + TEOA + H₂O system

The photochemical reduction of CO₂ was studied in a 1-ethyl-3-methylimidazolium tetrafluoroborate, triethanolamine and water ([Emim]BF₄ + TEOA + H₂O) system under visible light irradiation. The integration of CdS and the Co-bpy complex, which acted as a photocatalyst and cocatalyst, respectively, was employed as an efficient catalytic system for the CO₂-to-CO conversion. The utilization of [Emim]BF₄ and water took advantage of their green properties. The amount of CO production showed that the test medium containing 10 vol% H₂O was favourable for the catalytic performance of the CO₂ reduction. In order to further study the factors that influenced the current system, the physical and spectroscopy properties were characterized by altering the composition ratio of the ingredients. Relevant parameters, including the viscosity, conductivity, solubility and coordination, were adjusted using the ratio of the H₂O/[Emim]BF₄ addition, resulting in a different catalytic performance. All of these attempts led to an optimal reaction condition for the CO₂ reduction process.