Integrated CO2 Capture and Photocatalytic Conversion to Solar Fuels Using Multifunctional Materials

Photocatalytic conversion of CO₂ with H₂O to solar fuels is a promising technology to recycle CO₂, a major greenhouse gas. However, the CO₂-to-fuel conversion efficiency is typically low, mainly due to the fast recombination of photo-excited electron-hole pairs and limited absorption of solar spectrum by the photocatalyst. Some scientific challenges that have been overlooked in the literature are the photocatalyst’s ability to adsorb, activate and dissociate CO₂, as well as the adsorption/desorption kinetics on the catalyst surface.  To solve these problems, we have designed a new multifunctional material, porous microsphere MgO/TiO₂ that performs as a hybrid adsorbent/photocatalyst, and we operated the CO₂ photo-conversion temperature at around 150 ^oC.  The higher reaction temperature enhanced intermediate/product desorption, and the addition of MgO improves CO₂ adsorption at the MgO-TiO₂ interface, particularly in the presence of water vapor. This multifunctional material demonstrated a significantly enhanced and more stable activity than pure TiO₂ for CO₂ photoreduction to CO. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study was applied to identify surface intermediates and study the kinetics that is a critical factor governing the activity and stability of the photocatalyst. The effects of MgO morphology and dispersion on the TiO₂ surface are also investigated.