Browsing by Author "Baltrusaitis, Jonas"

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    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.
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    Investigation of the role of platinum oxide for the degradation of phenol under simulated solar irradiation
    (pplied catalysis B: environmental, 2013) Kibombo, Harrison S.; Wu, Chia-Ming; Peng, Rui; Baltrusaitis, Jonas; Koodali, Ranjit T.
    We demonstrate that a desired oxidation state can be achieved by synthetic colloidal methods and the choice of characterization technique is crucial for determining the physicochemical properties that influence the photocatalytic activities. XPS studies showed that PtO2 was realized in this study, and the resultant crystalline PtO2–TiO2 prepared by subsequent hydrothermal treatment demonstrated activity for phenol degradation under simulated solar light irradiation. Preformed platinum based TiO2 ensures control over the oxidation state and the crystallite size of titania. The role of Ptox in the form of stable Pt4+ is elucidated as a mild recombination center, whereas the crystallite size of Pt in surfactant free Pt0–TiO2 appears to be the overriding factor for attaining enhanced photocatalytic performance.
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    Synthesis-Dependent Oxidation State of Platinum on TiO2 and Their Influences on the Solar Simulated Photocatalytic Hydrogen Production from Water
    (The Journal of Physical Chemistry, 2013) Parayil, Sreenivasan Koliyat; Kibombo, Harrison S.; Baltrusaitis, Jonas; Koodali, Ranjit T.
    Platinized TiO2 photocatalysts of different compositions of Pt0 and PtO2 were prepared by modifying the synthesis procedures. The physicochemical properties of the composite materials were characterized by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. Energy dispersive X-ray spectroscopy measurements confirmed the presence of Pt species existing as PtO2 and/or mixtures of Pt0 and PtO2. The composite material, Pt–TiO2–2%H, contained a high amount of metallic Pt0 and PtO2 in close proximity with TiO2 that promoted an enhanced photocatalytic hydrogen evolution activity under simulated solar light irradiation. Although Pt–TiO2–2%C and Pt–TiO2–2%T consisted of similar compositions of PtO2, these oxidized platinum species seem to appear further apart from TiO2 in Pt–TiO2–2%C than Pt–TiO2–2%T. This caused dramatic variation in their optical behaviors such as strong fluorescence quenching and lower photocatalytic hydrogen evolution activity in the former photocatalyst. A photocatalyst prepared by the conventional photodeposition method was also prepared, characterized, and its photocatalytic activity assessed. This work provides an opportunity to understand the role of PtO2 for photocatalytic production of hydrogen from platinized TiO2 composites and the importance of heterojunctions in such photocatalysts for solar energy conversion.