Photoreduction of CO2 to liquid products with innovative photocatalysts

PHOTOREDUCTION OF CO2 TO LIQUID PRODUCTS WITH INNOVATIVE PHOTOCATALYSTS Matteo Tommasia,*, Mohammad Imteyaz Alama, Gianguido Ramisb and Ilenia Rossettia a. Chemical Plants and Industrial Chemistry Group, Dip. Chimica, Università degli Studi di Milano, CNR-SCITEC and INSTM Unit Milano-Università, via C. Golgi 19, 20133 Milan, Italy b. Dip. Ing. Chimica, Civile ed Ambientale, Università degli Studi di Genova and INSTM Unit Genova, via all’Opera Pia 15A, 16145 Genoa, Italy e-mail: matteo.tommasi@studenti.unimi.it Emission of CO2 caused by the use of fossil fuels has been widely considered as the anthropogenic primary contributor to the climate change. Lately, photocatalysis and in particular CO2 photoreduction (PR) has gained more and more attention [1] as a way to store solar energy. CO2 is used as reagent to produce different kind of liquid products, such as formic acid and methanol, in mild condition (80°C) in aqueous solution [2]. An innovative high pressure photoreactor allows to perform the reaction in aqueous phase up to 20 bar which increase the CO2 solubility and subsequently also the activity of the process. At first, the influence of different hole scavengers on the productivity has been investigated. TiO2 is cheap, non-toxic to humans, abundant and for these reasons it has been used as a reference [3]. Ammonia did not show any activity. P25 performances when using alcohols, vary greatly depending on the HS used. 2-propanol showed a HCOOH and a H2 productivity of 2401 mmol/kgcat h and 1478 mmol/kgcat h respectively, with the additional production of acetic acid. Then, different catalyst has been synthetized and tested to increase the productivity of the process. BaTiO3, CuO nanoparticles were synthesized by solvothermal process, ZnO by precipitation method and the CuO NPs have been deposited through impregnation. Pure WO3 and a composite of WO3/TiO2 have been synthetized through FSP. Bare BaTiO3 and 40% WO3/60% TiO2 showed the best performances with productivity of 36.9 mol/kgcath and 36.5 mol/kgcath respectively, which are outstanding results compared to the ones reported in literature. Lastly, glass tiles support has been designed, optimized and realized in stainless-steel through the use of 3D-printing technology. The latter allow to fit 12 slides coated with the desired catalyst in the reactor. The deposition procedure has been standardized, modification with Ag has been also performed and the obtained glass tiles have been tested towards the CO2 PR, showing good performance compared to P25 in form of powder. The deposited catalyst avoids the problem of the separation of titania from the liquid mixture and represents a starting point for the recycle and reuse of the photocatalysts. References 1. Li, K.; An, X.; Park, K.H.; Khraisheh, M.; Tang, J. A critical review of CO2 photoconversion: Catalysts and reactors. Catal. Today 2014, 224, 3–12, doi:10.1016/j.cattod.2013.12.006. 2. Shehzad, N.; Tahir, M.; Johari, K.; Murugesan, T.; Hussain, M. A critical review on TiO2 based photocatalytic CO2 reduction system: Strategies to improve efficiency. J. CO2 Util. 2018, 26, 98–122, doi:10.1016/j.jcou.2018.04.026. 3. Zhang, Z.; Bai, L.; Li, Z.; Qu, Y.; Jing, L. Review of strategies for the fabrication of heterojunctional nanocomposites as efficient visible-light catalysts by modulating excited electrons with appropriate thermodynamic energy. J. Mater. Chem. A 2019, 7, 10879–10897, doi:10.1039/c9ta02373a.