Investigation of process parameters for solar fuel production using earth-abundant materials

Photoreduction of CO2 to solar fuels and chemicals offers a sustainable method to produce net zero energy vectors. For large-scale applications, it is crucial to develop an improved understanding of the influence of reaction conditions on the design and optimisation of the photoreactor. The performance of CuO impregnated on BaTiO3 photocatalyst was investigated and compared to pristine BaTiO3, and CuO impregnated on commercial P25 (CuO/P25) and ZnO. The influence of irradiance, CO2 and H2O flow and partial pressure, and CO2/H2O ratio on the product yield and selectivity were examined. Using Design of Experiments and Computational Fluid Dynamic modelling, the optimised reaction conditions were irradiance of 125 mW cm−2, with a CO2 flow of 0.09 mL min−1, and water bubbler temperature of 25 °C. At these conditions, a 2 and 10-fold increase of CO and CH4 production, respectively, were obtained, compared to baseline conditions as well as exhibited the highest CO and CH4 production rate compared to previous reports. Among the earth-abundant photocatalysts, CuO/P25 had the highest quantum yield for CH4 (φCH4: 0.47), whilst CuO/BaTiO3 exhibited highest φCO (0.09) and stability for CO production. The under-performing of BaTiO3 and CuO/BaTiO3 was attributed to the presence of amorphous phase in BaTiO3. This work reveals that the combination of catalyst design, reaction engineering, and modelling can improve the efficiencies of CO2 photoreduction.