RODRIGO TEIXEIRA BENTO
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Artigo IPEN-doc 27737 On the surface chemistry and the reuse of sulfur-doped TiO2 films as photocatalysts2021 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; PILLIS, MARINA F.The surface chemistry and recyclability of sulfur-doped titanium dioxide (TiO2) films was evaluated. The photocatalysts were grown by metalorganic chemical vapor deposition (MOCVD) at 400 ◦C. The films were sulfur-doped at 50 ◦C by using hydrogen sulfide (H2S) as sulfur source. The photocatalytic behavior of the films was measure by monitoring the methyl orange dye decolorization under visible light for several cycles. The films are formed only for the anatase crystalline phase. The results demonstrated that no structural modifications or significant differences in the morphology of the films occurred after their use. The sulfur-doped TiO2 films presented good photocatalytic activity, with an efficiency of 72.1% under visible light in its first use. The durability experiments suggest that even with the dye impregnation on the catalyst surface, the photocatalytic activity of the S-doped TiO2 films remained around 70% in the first 3 cycles, which allows their practical application for water treatment and purification under sunlight.Artigo IPEN-doc 26655 Effect of nitrogen-doping on the surface chemistry and corrosion stability of TiO2 films2020 - SOUZA FILHO, EDVAN A. de; PIERETTI, EURICO F.; BENTO, RODRIGO T.; PILLIS, MARINA F.TiO2 and N-doped TiO2 films were grown on AISI 316 stainless steel substrates and on Si (100) by metallorganic chemical vapor deposition (MOCVD) at 400 ◦C and 500 ◦C. X-ray photoelectron spectroscopy, scanning electron microscopy, and contact angle techniques were used to characterize de films. The corrosion behavior was assessed by monitoring the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization tests in 3.5 wt% NaCl solution at room temperature. The results show that 6.18 at% of nitrogen was introduced in the films grown at 400 ◦C and 8.23 at% at 500 ◦C, and that besides TiO2, nitrogen phases were identified. All the films are hydrophilic and the contact angles varied from 48◦ to 72◦. The films presented good homogeneity, low porosity and rounded grains in the range of 40–90 nm. The RMS roughness varied between 5.5 and 18.5 nm. Titanium dioxide films grown at 400 ◦C showed better corrosion resistance than those grown at 500 ◦C due to its compact morphology. Nitrogen-doping was not efficient to protect the substrate from corrosion.