CO2 Photoconversion to Fuels and Chemicals under High Pressure

CO2 capture and storage is a fundamental research topic in order to decrease the concentration of such greenhouse gas. A new and challenging procedure is the CO2 photoreduction to alcohols and alkanes in the presence of a semiconductor. In this research, we tested a novel concept of photoreactor developed by our group1,2 able to operate under high pressure (up to 20 bar) and to explore different temperature ranges. Unconventional operating conditions were explored through this set up, so overcoming the key limitation of CO2 solubility in water and increasing the operating temperature, to improve the overall mass transfer inside the reactor. Na2SO3 was employed as inorganic hole scavenger. Besides reactor engineering optimization, several photocatalysts were investigated in order to solve the two main limitations of semiconductor application in photocatalysis: i) the inadequate visible light absorption of the UV-active catalysts; ii) the high electron-hole recombination rate. Au/TiO2 and CuO/TiO2 with different loadings (0.1-0.5 wt.%), preparation methods (deposition/precipitation, impregnation and Flame Spray Pyrolysis), and polymorphs (anatase, rutile) were chosen as photocatalysts. Characterization of fresh and spent samples was carried out by traditional techniques (XRD, BET, TEM, UV) combined with specific in situ analysis (DRIFTS). The operating conditions (pressure, temperature, pH, irradiation power) and photocatalysts have been varied allowing the investigation of the whole process several possible applications of this reactor. In particular focusing on the maximization of gas (H2 and CH4) and liquid (CH3OH, HCHO, HCOOH) products. Keywords: CO2 photoconversion, gold photocatalysts, copper oxide photocatalysts, high pressure photocatalysis. References (1) Rossetti, I.; Villa, A.; Pirola, C.; Prati, L.; Ramis, G. A Novel High-Pressure Photoreactor for CO2 Photoconversion to Fuels. RSC Adv. 2014, 4 (55), 28883–28885. (2) Rossetti, I.; Villa, A.; Compagnoni, M.; Prati, L.; Ramis, G.; Pirola, C.; Bianchi, C. L.; Wang, W.; Wang, D. CO2 Photoconversion to Fuels under High Pressure: Effect of TiO2 Phase and of Unconventional Reaction Conditions. Catal. Sci. Technol. 2015, 5, 4481–4487.