Photocatalytic CO2 reduction testing

MeCN/H₂O/TEOA (3:2:1, 6 mL) mixed solution containing 7.5 mg [Ru (bpy)₃]Cl₂·6H₂O photosensitizer and 1 mg as-prepared cocatalysts was added into a gas-closed quartz reactor. Then, the quartz reactor was purged with CO₂ (99.9999% or 10%) for 30 min. A 300 W Xe lamp (PLS-SXE300D, Perfectlight) with UV cutoff filter (λ ≥ 420 nm) was applied to as the light source and the light intensity was measured to be 405 mW cm⁻². The reactor temperature was hold at room temperature by an electronic fan. For each 2 h, the gaseous products were analysed by gas chromatography (GC 2014C, Shimadzu). H₂ was analyzed by a thermal conductivity detector (TCD). CO was converted to CH₄ using a methanation reactor and then detected by a flame ionization detector (FID). The liquid products were analysed using ¹H NMR. Isotope test was conducted by gas chromatography-mass spectrometry (GC-MS, 7890B and 5977 A, Agilent). The AQE was calculated according to the equation: AQE = [(2 × number of CO evolved molecules)/(number of incident photons)] × 100%. The turnover number (TON) for CO over Ru atoms was calculated using the following equation: TON = moles of CO evolved/moles of Ru atoms on photocatalyst. For recycling tests, the sample was collected and rinsed with DI water three times after 2 h of photocatalytic reaction. Then, the fresh reaction solution containing 7.5 mg Ru-dye was mixed with the used cocatalysts to conduct the second cycle experiment. By analogy, the subsequent four recycling tests were conducted.