Dual-functional Nb2O5 and Nb2O5-TiO2 materials for simultaneous CO2 reduction and organic substance oxidation to value-added compounds

Fossil fuels are still the leading energy source in the world, which constitute a major source of CO2 emissions. The rising concentration of CO2 in the atmosphere is a growing concern due to its effects on climate and is considered as the leading cause of climate change. To mitigate the negative influence of greenhouse gases, it is imperative to reduce CO2 emissions and possibly reduce the existing CO2 concentration in the atmosphere. A search for alternative sources of energy is a viable solution to this problem. As the Sun provides us with abundance of energy, harvesting even a fraction of it would satisfy all our current energy needs. Harnessing solar energy and converting it into useful chemicals can be done via photocatalysis using a material that catalyses certain reactions when exposed to irradiation — a photocatalyst. Photocatalytic reduction of CO2 into energy-rich compounds (methane, methanol and ethanol) not only transforms sunlight into chemical energy, but has an added benefit of reducing the existing concentration of CO2 in the atmosphere. While CO2 reduction reaction with photocatalysis alone has two positive impacts, the oxidation half-reaction using photogenerated holes is left unutilized. However, with precise engineering of a photocatalyst, oxidation half-reaction can be used to produce value-added organic compounds, while the reduction half-reaction drives the production of energy-rich compounds from CO2. Much work has been done in recent decades on the photocatalysts, however, certain challenges still remain, namely: low efficiency of conversion into desired products, low absorption of visible light (and thus low efficiency) and low selectivity of catalyzed reactions. We will address these problems in the project by developing novel photocatalysts for simultaneous reduction of CO2 and oxidation of alcohols into value-added compounds. To this end we will prepare and investigate: 1) solid and mesoporous Nb2O5 nanoparticles with non-noble metal cocatalysts, 2) Nb2O5 and TiO2 hollow spheres with spatially separated reduction and oxidation cocatalysts and 3) Nb2O5-TiO2 heterojunctions. We will investigate the influence of synthesis parameters and post-synthesis modifications on the properties of the photocatalysts and on the activity and selectivity in reduction of CO2 to energy-rich compounds and oxidation of alcohols to value-added compounds. Investigation supported by simulations using DFT will enable us to establish relationships between structure, properties and activity of the prepared photocatalysts, thus contribute towards understanding, development of the photocatalysts and eventual progress from laboratories into real-world applications.