Browsing by Author "Rasalingam, Shivatharsiny"
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Item Competitive role of structural properties of titania–silica mixed oxides and a mechanistic study of the photocatalytic degradation of phenol(environmental, 2014) Rasalingam, Shivatharsiny; Kibombo, Harrison S.; Peng, Rui; Koodali, Ranjit T.TiO2–SiO2 mixed oxide materials were hydrothermally synthesized and the photocatalytic degradation of phenol under UV-irradiation was evaluated. We also demonstrated that varying the co-solvent, modulates the structural properties of the materials. In particular, the use of non-polar co-solvents such as toluene seemed to increase the crystallinity, surface area, and pore diameter while the crystallite size of titania seemed to change little. A comprehensive characterization using surface and bulk techniques evidenced the role of porosities, crystallinity, and Ti–O–Si linkages of the mixed oxides as significant factors that contribute to the degradation of phenol. The TiO2–SiO2 mixed oxide material prepared using only ethanol as the solvent showed 24% degradation of phenol after 120 min of irradiation whereas other mixed oxide materials degraded phenol more efficiently (57% to 100%) in the same duration of time. The higher photocatalytic activities of the mixed oxide materials prepared using non-polar solvents is attributed to a combination of factors that include higher Apparent Surface Coverages of Ti–O–Si heterolinkages, larger pore sizes, and most importantly higher crystallinities of the titania phase. Larger pore sizes enabled better transport of reactant molecules and products to and from the active sites (Ti–O–Si heterolinkages) and the higher crystallinities of the titania phase helped in minimizing the electron–hole recombination in these photocatalysts, and thus resulted in high degradation efficiencies.Item Facile template free method for textural property modulation that enhances adsorption and photocatalytic activity of aperiodic titania supported silica materials(Applied Catalysis B: Environmental, 2013) Kibombo, Harrison S.; Rasalingam, Shivatharsiny; Koodali, Ranjit T.A series of aperiodic titania–silica photocatalysts were prepared in ethanolic solutions of co-solvents such as ethyl acetate (EtOAc), acetonitrile (ACN), acetone (ACT), and N,N′-dimethylformamide (DMF) using a combination of sol–gel chemistry and mild hydrothermal conditions. Extensive structural characterization emerged critical in demonstrating that the incorporation of such polar aprotic solvents is a viable approach for the enhancement and modulation of textural properties such as surface areas and pore sizes without the use of expensive templates. These studies revealed that the dark adsorption capacities of Rhodamine B (RhB) dye were dependent on the pore volume, and had minimal role on the photocatalytic degradation of the dye molecules. However, photocatalysts with large pore diameters exhibited improved initial degradation rates, suggesting that the sizes of the pores through which organics can diffuse in and out of the mesostructure are vital for their effective photocatalytic degradation under visible light irradiation. This work provides an insight into the use of facile preparation methods for the design of photocatalysts of desired porosities that are optimal for application in areas such as persistent organic pollutant remediation in waste water management.Item Influence of Ti–O–Si hetero-linkages in the photocatalytic degradation of Rhodamine B(Catalysis communications, 2013) Rasalingam, Shivatharsiny; Kibombo, Harrison S.; Wu, Chia-Ming; Baltrusaitis, Jonas; Koodali, Ranjit T.The influence of Ti–O–Si hetero-linkages in the degradation of Rhodamine B (RhB) dye over TiO2–SiO2 xerogels is exemplified by XPS analysis. We demonstrate a relationship between the percentage surface content of Ti–O–Si and the rate of photocatalytic degradation of RhB. Our detailed surface investigation revealed that the overall degradation of RhB is enhanced due to the high surface percentage content of Ti–O–Si species, high crystallinity of titania phase, and its effective dispersion on a high surface area porous silica support.Item Versatility of heterogeneous photocatalysis: synthetic methodologies epitomizing the role of silica support in TiO2 based mixed oxides(Catalysis Science & Technology, 2012) Kibombo, Harrison S.; Peng, Rui; Rasalingam, Shivatharsiny; Koodali, Ranjit T.Heterogeneous photocatalysis continues to be an active area of research with focus on developing catalytic systems that can degrade toxic pollutants in the gas and aqueous phase, and split water to generate hydrogen and oxygen. In this review, the incorporation of silica phases in titanium dioxide based photocatalysts is reviewed.