Strategies for improving CO2 photoreduction under solar light

Abstract

Carbon dioxide is an abundant greenhouse gas accounting for 79% of global warming. To reduce its concentration, it is important to implement strategies such as the conversion into high value-added products such as fuels and chemicals, like methane. Due to carbon dioxide inertness and low reactivity, additional energy is required for its activation. Photocatalysis, specifically CO2 photoreduction with water vapor, exploits solar energy as an abundant, unlimited, renewable energy source, and enhance carbon dioxide conversion into different solar fuels, without requiring additional energy input to make the reaction take place. The aim of my research is the study of BaTiO3 and CaTiO3 perovskites that are gaining attention, in virtue of the good photostability, corrosion resistance, photocatalytic properties and the intrinsic basicity. Therefore, the catalysts were synthetized by the hydrothermal method. Two strategies were used: the first was doping perovskites with nitrogen and carbon, the second was associating a co-catalyst with the semiconductor aiming to exploit the full sunlight spectrum and increase the light absorption range of the selected catalysts. All the materials were characterized through FT-IR, DRS, SEM-EDX, TEM, N2 physisorption, and XRD techniques and then tested in both gas and liquid phase under both solar and UV light to correlate their photoactivities with their physical, chemical, and optical properties. From the experimental data it can be proved that nitrogen and carbon doped catalysts enhanced photoreactivity towards methane under solar light. Also, carbon dots exhibited activity if irradiated by both UV and solar light.