Photocatalytic reduction of CO2 over Bi2WO6 in a continuous-flow differential photoreactor: Investigation of operational parameters

Abstract

Carbon dioxide (CO2) photoreduction is a complex process and, despite significant efforts in photocatalyst development, an investigation of the influence of process parameters on photoreduction is still necessary. In this work, a Bi2WO6 photocatalyst was used for the photocatalytic reduction of CO2 in a continuous-flow differential photoreactor and a rotational central composite design (RCCD) was employed for a systematic evaluation and optimization of the operational parameters. The experimental parameters considered were CO2 flow rate, light intensity, partial pressure of H2O, and amount of photocatalyst. The synthesized Bi2WO6 was characterized by XRD, XPS, Raman, SEM, BET measurements and UV–vis spectroscopy. The results showed that the CO2 flow rate had an impact on CO2 photoreduction; the light intensity, partial pressure of H2O, and amount of photocatalyst significantly influenced the CO cumulative production. At optimum conditions (120 mW cm−2, 2.7kPa, and 15 mg), it was possible to obtain a 60% enhancement in photocatalytic efficiency, compared to the results obtained before the experimental design. Characterization studies carried out after the use of the photocatalyst showed that Bi2WO6 experienced changes on its surface, which may explain the deactivation observed during the photoreduction under gaseous flow.