A novel PEBAX-1657/PES-(BiFeO3@ZnS) photocatalytic membrane for integrated hybrid systems coupling CO2 separation and photoreduction

Abstract

Suspended photocatalyst systems face the problems of poor light distribution, photocatalyst separation, and inappropriate transfer of reducing agent and CO2 gas to the active photocatalyst sites. To overcome these issues, Poly(ether-block-amide)−1657/Polyethersulfone (PEBAX-1657/PES) -(BiFeO3 @ZnS) photocatalytic membrane was synthesized and applied for simultaneous separation and photoreduction of CO2 to methanol as the valuable product. The two-phase membrane photoreactor was tested under both ultraviolet (UV) and visible light irradiation in the presence of water. Based on UV–visible and photoluminescence spectroscopy (PL) analyses, PEBAX-1657/PES-(BiFeO3@ZnS) exhibited wider light absorption range and lower recombination rate of photogenerated species compared with pristine PEBAX-1657/PES, respectively. Meanwhile, the separation features of the photocatalytic membrane remained almost constant even after 6 h reaction time. In addition, the schematic representation of proposed mechanism was clarified in detail based on the p-n junction photogenerated charge carrier transfer process of BiFeO3@ZnS. Finally, photocatalytic performance of the prepared photocatalytic membrane with different water flow rates and light powers were examined. The photocatalytic activity tests revealed the maximum methanol concentrations of 0.85 mmol/L and 0.56 mmol/L and the maximum methanol production yields of 5100 and 3360 µmol/gcat.h under UV and visible irradiation, respectively at the optimized operating conditions (water flow rate of 3 mL/min and light power of 250 W). Therefore, the present study provides a new insight into the effective visible-light-driven photocatalytic membranes for simultaneous separation and photocatalytic conversion of CO2 to solar fuels.