(549f) The Role of Carbon Nanotubes in Photocatalytic Conversion of CO2/H2O and CO2/CH4 Systems to Syngas

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

The significance of photocatalysis in becoming one of the solutions in solving major air and water pollution problems has been increasing. In fact, NASA has been implementing photocatalytic technology in purifying air and water since 2011 and plans to use this technology in converting CO2 to fuels using solar light for In-Situ Resource Utilization (ISRU) Mars energy production. In addition, as part of Global Burden of Disease Project in Institute for Health Metrics and Evaluation, it was indicated that 5.5 million people die annually prematurely because of air pollution. Where in, air pollution caused primarily due to power plants, factories, and vehicle exhausts. Therefore, considering the significant role that photocatalysis plays currently and futuristically in air and water purification and alternative fuel production, it becomes increasingly necessary to optimize photocatalytic processes.

Our research work has led to the understanding and optimization of photocatalysis and photocatalytic processes through the synthesis of highly stable and highly efficient photocatalyst, chiefly for reducing CO2. The photocatalyst that we have produced contains single walled carbon nanotubes (CNT) doped onto titanium nanorods and have shown to convert mixtures of CO2/H2O and CO2/CH4 to synthesis gas (CO and H2) at low temperatures (100 – 150 °C) and pressures (1 – 3 atm) using visible light. Surfactants were employed to effectively disperse the carbon nanotubes. These dispersions allow for the de-bundling of CNT’S, providing large surface areas for other particles to come into contact. Therefore, the effects of three surfactants (SDS, SDBS, and CTAB) were studied to efficiently disperse carbon nanotubes with titanium dioxide nanoparticles. The synthesized catalysts were characterized using SEM, TEM, UV-VIS DRS, XRD, and FTIR. The reaction was carried out in an annular photochemical reactor using a 12 watt LED white light. The changes in CO2 concentration in the product gas were determined using GC/TCD.

In terms of optimizing the photocatalyst, the role of CNT in visible light driven photocatalysis was explored. There appears to be a synergistic effect which occurring between the TiO2/CNT that results in lower band gap energies (~2 eV). Implementation of the CNT’S have shown to have the following results for carbon dioxide conversion: 1) red shift of photocatalytic reaction, 2) Better adsorption of CO2 because of their nano-hollow structures including both SWCNT and MWCNT, and 3) longer lifetime of electron-hole separation because of its structure and large electron storage capacity.