Studies of photocatalytic reduction of carbon dioxide for renewable fuel production using niobium oxide

Reference	Presenter	Authors (Institution)	Abstract
05-012	Joao Otávio de Sousa Mendes	Mendes, J.O.(Federal University of São Carlos /Brazilian Agricultural Research Corporation); Carvalho, K.T.(Brazilian Agricultural Research Corporation); da Silva, G.T.(Federal University of São Carlos /Brazilian Agricultural Research Corporation); Ribeiro, C.(Brazilian Agricultural Research Corporation, São Carlos, SP, Brazil);	Using CO2 as feedstock for production of chemical compounds of high added value can play an important role in mitigating global warming by reducing the emissions of this gas in localized conditions. However, chemical reactions involving CO2, an inert molecule, require a large amount of energy. Photocatalytic process intermediated by semiconductor oxides can provide a viable rote for CO2 conversion. For this study, the photoactivity of Nb2O5 nanoparticles was tested. Nb2O5 powders were obtained by oxidant peroxo method using hydrothermal treatment for crystallization of the nanoparticles. Typically, 2g ammonium niobium oxalate was dissolved in 4mL of H2O2 and 100mL of H2O. This solution was transferred to an autoclave and kept at 120°C for 12h under magnetic stirring. The solid obtained was centrifuged and dried for 12h at 60°C. After the physical-chemical characterization, 50mg of powdered photocatalyst was irradiated using an 18W UV lamp in a 30mL batch gas/solid photoreactor containing CO2 and water vapor. Products were monitored at regular intervals by gas chromatography. Results show highly preferential CO formation during the first 6h of reaction. However, the formation of an increasing amount of CH4 is observed as the reaction time goes by and by the end of 24h a total of 1514?mol/g of CO and 94?mol/g of CH4 was obtained. Compared to the standard TiO2 (P25) under the same conditions, the amounts of CO and CH4 produced over Nb2O5 were 9x higher and 4x higher, respectively. Moreover, Nb2O5 is a non-toxic oxide formed by highly abundant elements that can be easily obtained by hydrothermal synthesis, having the potential to be produced on a large scale. Further studies are being carried out to improve the photoactivity of Nb2O5, as well as its selectivity to CO or CH4, as both products can be of industrial interest. Such studies include the formation of heterostructures and the use of photoelectrochemical methods for band position adjustments.
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