RESUMO
Propylene carbonates are important organic solvents and feedstocks for different applications, including synthesis of polymers and Li-batteries. The generation of propylene carbonate utilising anthropogenic CO2 and renewable solar energy offers an alternative sustainable process with a closed loop carbon cycle. The development of microstructured photocatalysts with desired properties, including high degree of product selectivity, wide range of optical properties, and maximised conversion yield, plays an important role for effective production of propylene carbonate from CO2. A hierachical hollow core with a double shell of TiO2-x-Cu2O-CuO was fabricated using the versatile solvothermal-microwave synthesis method. The fabricated sample revealed effective cascading of photogenerated electrons and holes that promoted the conversion of propylene carbonate (i.e., 1.6 wt%) under 1 Sun irradiation.
RESUMO
TiO2-x/W18O49 with core-shell or double-shelled hollow microspheres were synthesized through a facile multi-step solvothermal method. The formation of the hollow microspheres with a double-shell was a result of the Kirkendall effect during the solvothermal treatment with concentrated NaOH. The advanced architecture significantly enhanced the electronic properties of TiO2-x/W18O49, improving by more than 30 times the CO2 photoreduction efficiency compared to the pristine W18O49. Operando DRIFTS measurements revealed that the yellow TiO2-x was a preferable CO2 adsorption and conversion site.
RESUMO
To improve the CO2 adsorption on the photocatalyst, which is an essential step for CO2 photoreduction, solid solutions were fabricated using a facile calcination treatment at 900 °C. Using various alkalis, namely NaOH, Na2CO3, KOH, K2CO3, the resulted samples presented a much higher CO2 adsorption capacity, which was measured with the pulse injection of CO2 on the temperature programmed desorption workstation, compared to the pristine Evonik P25. As a result, all of the fabricated solid solutions produced higer yield of CO under UV light irradiation due to the increased basicity of the solid solutions even though they possessed only the rutile polymorph of TiO2. The highest CO2 adsorption capacity under UV irradiation was observed in the sample treated with NaOH, which contained the highest amount of isolated hydroxyls, as shown in the FTIR studies.
RESUMO
Anthropogenic CO2 is the main contributor to the increased concentration of greenhouse gases in the atmosphere, and thus utilising waste CO2 for the production of valuable chemicals is a very appealing strategy for reducing CO2 emissions. The catalytic fixation of CO2 with epoxides for the production of cyclic carbonates has gained increasing attention from the research community in search of an alternative to the homogeneous catalytic routes, which are currently being used in industry. A novel photocatalytic heterogeneous approach to generate cyclic carbonates is demonstrated in this work. Hyper-branched microstructured Ru modified TiO2 nanorods decorated with RuO2 nanoparticles, supported on fluorine-doped tin oxide (FTO) glass were fabricated for the first time and were used to catalyse the photo-generation of propylene carbonates from propylene oxides. Propylene carbonate was used as a reference for cyclic carbonates. The photo-generation of cyclic carbonates from epoxides and CO2 was carried out at a maximum temperature of 55 °C at 200 kPa in a stainless steel photoreactor with a quartz window, under solar irradiation for 6 h. The best performing photocatalyst exhibited an estimated selectivity of 83% towards propylene carbonates under the irradiation of a solar simulator.