(600cd) CO2 Photoreduction Key Step Study: The Adsorption of CO2 On TiO2 Surfaces in the Presence of Co-Catalyst

Using solar energy to convert  to hydrocarbon fuels has been a promising area of research since it addresses two major challenges facing the planet: production of renewable energy while reducing CO2 emissions. However, the hydrocarbon production rate achieved so far is still in the µmol/hr  range[1]. Therefore it is desirable to search for new photocatalysts that can enhance the conversion of CO2. Titania with added metal co-catalysts is a promising approach for enhancing the reaction rate. It is believed that the reduction of  to  on the TiO₂ surface is the first and important step for  photoreduction mechanism[1, 2]. This key step relies on the  adsorbed forms on the TiO₂ surface. Smaller  bond angles facilitates the transfer of photoexcited electrons from TiO₂ to CO₂ due to the lowering of  LUMO energy level[3]. Many research groups have studied the appropriate TiO₂ surfaces for favored  adsorbed forms which facilitate this electron transfer [4-6]. However the effect of co-catalyst on TiO₂surfaces on the CO2 bond breaking have not been studied in the past.

The main objective of this work is to study the effect of Ag co-catalyst on TiO₂ for  photoreduction in order to design specific reaction surfaces that could interact sufficiently with the  to form smaller angle  adsorbed species. We consider (001), (101), and (100) surfaces of anatase, and (110) and (011) surfaces of rutile with Ag present. The adsorption sites for Ag and  were chosen based on  literature[6-9]. Gaussian (for cluster model) and Vienna Ab Initio Simulation package (VASP)(for periodic model), are  both  used to study the various adsorbed forms of CO2 on TiO₂ . The existence of co-catalyst on the model surfaces influences the interactions between  and TiO₂ surfaces. The goal is to achieve a better understanding of the bond cleavage mechanism in order to design more efficient photocatalysts for  reduction to light hydrocarbon fuels.

References

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