(617dz) Novel Catalysts for Photocatalytic Conversion of CO2/H2O and CO2/CH4 Systems to Syngas

Novel Catalysts for the Photocatalytic Conversion of CO2/H2O and CO2/CH4 Systems to Syngas 

Karishma Piler, Paul Bernazzani, Cristian Bahrim, and Tracy J Benson.

In accordance with EPA, Carbon dioxide accounts for ~ 81 % of all U.S. greenhouse gas emissions in 2014. According to NASA global climate change, for the first time in the recorded history CO2 levels have surpassed 400 ppm in 2013. While many researchers are searching for capture and storage methods for reducing CO2 emissions, identifying methods to effectively convert CO2 to saleable products, CO2 can then become a valuable feed stock for sustainable energy production. This research will present the use of pairing of Titania nanotubes with single walled carbon nanotubes in photocatalytic conversion of carbon dioxide in water/CO2 and methane/CO2 systems into useful fuels and chemicals. The reaction was carried out in a continuous flow annular heterogeneous reactor in the presence of UV and visible light.

Titanium dioxide as a photocatalyst has been studied and implemented for a long period of time, chiefly in the production of hydrogen and other chemicals through water splitting, decomposition of bacteria and organic waste, and carbon dioxide conversion. Titanium dioxide has been doped with various metals and non-metals to engineer the band gap for effective light harvesting and to increase the time of electron-hole pair recombination so as to bring in a large increase in the efficiency of energy production through photocatalysis.

In this research, titania nanotubes have been used because of their high specific surface area for interaction and optimum pore size for diffusion of active species. Also, because of their nanotube architecture, the recombination effect is greatly reduced. The reasons for implementing carbon nanotubes is because of their properties such as large surface area, one dimensional electron transfer, and large electron storage capacity easily accepting photo-excited electrons. They also act as photosensitizers for TiO2. They can adsorb twice the CO2 adsorbed compared to activated carbon, another significant asset. The reason behind pairing of titanium dioxide nanotubes and carbon nanotubes was to observe and implement the synergistic effects which can result from combination of their unique properties in photocatalytic conversion of CO2 to useful products.

The pairing of titanium dioxide nanoparticles and metallic carbon nanotubes along with providing several surface irregularities which act as trap states for electrons, it also leads to a distinctive quantum effect called the schottky barrier, a space charge separation region at the interface of TiO2-CNT that increases the recombination time of electron-hole pairs. This results in TiO2 acquiring a strong positive charge and metallic single walled carbon nanotube (SWCNT) a strong negative charge. The Ti-O-C bond results in the shift from UV to Visible wavelength region.

In this presentation, we will present the characterizations of the photo-catalyst, including FTIR, Raman, TEM, and XRD, as well as the reaction results, namely the conversion of CO2. Reactions were conducted at 100 â?? 120 °C, and a GC-TCD was used to analyze the conversion of CO2 and the formation of CO, H2, and low molecular weight hydrocarbon gases.