Perovskite-based catalysts for CO2 photoreduction reaction

Perovskite-based catalysts for CO2 photoreduction reaction I. Martin1*, G. Forghieri2, E. Ghedini2, I. Rossetti3, M. Signoretto2 1Functional Nanosystems, Italian Institute of Technology, Via Morego 30, 16163 Genoa, Italy 2Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice and INSTM RU of Venice, Via Torino 155, 30172 Venice, Italy 3Chemical Plants and Industrial Chemistry Group, Chemistry Department, University of Milan, CNR-SCITEC ans INSTM RU of Milan, Via C. Golgi 19, 20133 Milan, Italy *Corresponding Author’s E-mail address: irene.martin@iit.it Introduction. The worrying rise in greenhouse gas emissions has led to the necessity of limiting the consumption of fossil sources on one hand, and on the other to develop new technologies for capturing, storing and utilising these gases [1]. In this perspective, CO2 photoreduction, paired with water splitting, presents a great potential for the synthesis of fuels and other building block molecules of high value, e.g. methane (CH4), carbon monoxide (CO) and other C1-based products [2]. To develop an effective and selective photocatalytic system, the perovskite barium titanate (BaTiO3) was chosen as a new promising photoactive material with respect to other common photocatalysts, e.g. titanium dioxide (TiO2) and zinc oxide (ZnO). Copper (II) oxide was introduced as a co-catalysts to hinder charge recombination [3], enhacing the activity and selectivity of the perovskite. Experimental/methodology. BaTiO3 was synthesized by hydrothermal method, modified from literature [4], and was compared with commercial TiO2 (Degussa P25, Evonik) and a lab-synthesized ZnO (synthesized by precipitation [5]). CuO was synthesized by hydrothermal method [6] and introduced as a co-catalyst by impregnation (2.5 wt%) on BaTiO3, TiO2 and ZnO. The photocatalysts were tested in a gas and liquid phase. Results and discussion. Experiments performed in gas phase resulted in the production of methane and hydrogen, in accordance with the proposed reaction mechanism [7]. Pristine BaTiO3 was less active with respect to TiO2 (79 vs 104 μmol gcat-1 h-1 of CH4, respectively), but the presence of CuO both improved both its activty and resulted in a minor H2 production with respect to CuO/TiO2 (221 vs 169 μmol gcat-1 h-1 of CH4 and 239 vs 414 μmol gcat-1 h-1 of H2, repectively). Experiments performed in liquid phase under neutral pH resulted in the production of formic acid and methanol [7], whereas under basic pH only HCOOH was detected. The basic enviroment also provided a ten-fold total productivity in C-based molecules with respect to pH 7. Under these reaction conditions, the materials showed similar activity and the introduction of CuO did not lead to significant improvements. Thus it is possible to argue that CO2 photoreduction performed in liquid phase is driven by reaction conditions, whilst in gas phase the choice of the appropriate photocatalyst can redirect the activity and selectivity of the reaction. References [1] Riahi, K. et al. IPCC, 2022: Mitigation of Climate Change, Contribution of Working Group III to the Sixth Assessment Report of Intergovernmental Panel on Climate Change, Cambridge, UK and New York, NY, USA 2022. [2] Gür, T.M. Progress in Energy and Combustion Science 2022, 89, 1009657. [3] Nogueira, A.E. Catalyis Communications 2020, 137, 105929. [4] Kwak, B.S. and Kang, M. Journal of Nanoscience and Nanotechnology 2017, 17, 7351-7357. [5] Thompson, W.A. et al. RSC Advances 2019, 9, 21660. [6] Chandrasekar, M. et al. Journal of Kind Saud University – Science 2022, 34, 101831. [7] Olivo, A. et al. Energies 2017, 10, 1394.