Sapanbir S. Thind

Significant enhancement in the photocatalytic activity of N, W co-doped TiO2 nanomaterials for promising environmental applications

In this work, a mesoporous N, W co-doped TiO(2) photocatalyst was synthesized via a one-step solution combustion method, which utilized urea as the nitrogen source and sodium tungstate as the tungsten source. The photocatalytic activity of the N, W co-doped TiO(2) photocatalyst was significantly enhanced by a facile UV pretreatment approach and was evaluated by measuring the rate of photodegradation of Rhodamine B under both UV and visible (λ > 420) light. Following the UV pretreatment, the UV photocatalytic activity of the N, W co-doped TiO(2) was doubled. In terms of visible light activity, the UV pretreatment resulted in an extraordinary >12 fold improvement. In order to gain insight into this substantial enhancement, the N, W co-doped TiO(2) photocatalysts were studied using x-ray diffraction, transmission electron microscopy, N(2) physisorption, UV-vis absorbance spectroscopy and x-ray photoelectron spectroscopy prior to and following the UV pretreatment. Our experimental results have revealed that this significant augmentation of photocatalytic activity may be attributed to several synergetic factors, including increase of the specific surface area, reduction of the band gap energy and the removal of carbon impurities.

Quantitative structure-reactivity study of electrochemical oxidation of phenolic compounds at the SnO2-based electrode.

In the present study, the electrochemical oxidation of 22 phenolic compounds was systemically examined at the RuO(2)-SnO(2)-Sb(2)O(5) electrode to elucidate the inherent structure-reactivity correlation. The oxidation process was monitored in situ by UV-vis spectroscopy. A variety of substituents (e.g., -CH(3), -NH(2), -Cl, -OH, -COOH, -NO(2), -CHO) were employed in order to cover various possible electronic effects. Our experimental results revealed that the relationship between the Hammett constant and rate constant for the electrochemical oxidation of phenolic compounds at the RuO(2)-SnO(2)-Sb(2)O(5) electrode was different from the results obtained at a platinum electrode. The substituted phenols with electron-withdrawing groups were electrochemically oxidized more rapidly than those with electron-donating groups. To decipher the effects of physiochemical properties on the electrochemical reactivity of phenolic compounds, 140 molecular descriptors were calculated and assessed for each phenolic compound; a quantitative structure property relationship (QSPR) model was developed. Correlations between the rate constants and quantum properties of the phenolic compounds were achieved using partial least-squares (PLS) analysis. The most crucial quantum descriptors responsible for the electrochemical reactivity of phenolic compounds were determined to be E(HOMO), chemical potential, total dipole, quadrupoles, subgraph counts, relative positive charged surface area, and pK(a). The proposed QSPR model was based on the quantum descriptors derived from the whole molecule, providing lucid explanation and effective prediction of the electrochemical reactivity of various phenolic compounds.

Facile synthesis of mesoporous carbon nitride and titanium dioxide nanocomposites with enhanced visible light photocatalytic activity

A facile and efficient solution combustion method was developed and employed in the fabrication of novel mesoporous carbon nitride and titanium dioxide (C3N4–TiO2) nanocomposites as advanced photocatalysts for wastewater remediation. Urea was used as the precursor of C3N4, while titanium tetra-isopropoxide served as the source of titanium. Yellow nanocomposites were produced as compared to the formed white TiO2 and C3N4 nanomaterials. Transmission electron microscopic images and N2 adsorption/desorption analysis revealed that the fabricated nanocomposites possessed a mesoporous structure and much larger surface areas as compared to the individual constituents. X-ray photoelectron spectroscopic measurements and thermogravimetric analysis were utilized to determine the composition and thermal stability of the C3N4–TiO2 nanocomposites. Tauc plots derived from the UV-vis absorption spectra revealed that the formation of the C3N4–TiO2 nanocomposites significantly narrowed the band gap energy, leading to a high visible light response in contrast to the individual TiO2 (∼3.2 eV) and C3N4 (∼2.8 eV) samples. The optimal composition of the C3N4–TiO2 nanocomposites was determined, and the new nanocomposite developed in this study exhibited high visible light activity in the photochemical oxidation of Rhodamine B, as compared to the mechanically mixed C3N4 and TiO2 sample. This significant improvement in photocatalytic activity may be attributed to the synergistic effects of the red shift in absorption and the large surface area.

Photoelectrochemical degradation of acetaminophen and valacyclovir using nanoporous titanium dioxide

Electrochemically treated nanoporous TiO 2 was employed as a novel electrode to assist in the photoelectrochemical degradation of acetaminophen and valacyclovir. The prepared electrode was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Cyclic voltammetry (CV), Mott-Schottky plots, ultraviolet-visible light (UV-vis) absorbance spectroscopy, and a total organic carbon (TOC) analyzer were employed to investigate the photoelectrochemical degradation of acetaminophen and valacyclovir. The results indicated no obvious removal of acetaminophen and valacyclovir over 3 h when separate photochemical degradation and electrochemical oxidation were employed. In contrast, acetaminophen and valacyclovir were rapidly eliminated via photoelectrochemical degradation. In addition, electrochemically treated nanoporous TiO 2 electrodes significantly enhanced the efficacy of the photoelectrochemical degradation of acetaminophen and valacyclovir, by 86.96% and 53.12%, respectively, when compared with untreated nanoporous TiO 2 electrodes. This enhanced performance may have been attributed to the formation of Ti 3+ , Ti 2+ , and oxygen vacancies, as well as an improvement in conductivity during the electrochemical reduction process. The effect of temperature was further investigated, where the activation energy of the photoelectrochemical degradation of acetaminophen and valacyclovir was determined to be 9.62 and 18.42 kJ/mol, respectively.

Efficient bacterial disinfection based on an integrated nanoporous titanium dioxide and ruthenium oxide bifunctional approach

The increasing lack of drinking water around the globe is of great concern. Although UV irradiation, photocatalysis, and electrocatalysis for bacterial disinfection have been widely explored, the synergistic kinetics involved in these strategies have not been reported to date. Herein, we report on an efficient and cost-effective strategy for the remediation of a model bacterium (E. coli), through the integration of photochemistry and electrochemistry based on a bifunctional electrode, which utilizes titanium (Ti) as the substrate, nanoporous titanium dioxide (TiO2) as a photocatalyst, and ruthenium oxide (RuO2) nanoparticles as an electrocatalyst. The nanoporous TiO2 was grown directly onto a Ti substrate via a three-step anodization process, and its photocatalytic activity was significantly enhanced by a facile electrochemical treatment. A high disinfection rate at 0.62 min-1, with >99.999% bacterial removal within 20 min was achieved using the novel TiO2/Ti/RuO2 bifunctional electrode. Complete bacterial disinfection was attained within 30 min as assessed by a spread plate method. Bacterial survival strategies, including a viable but non-culturable state of the bacteria, were also investigated during the bifunctional treatment process. The novel strategy demonstrated in this study has strong potential to be utilized for water purification and wastewater treatment as an advanced environmentally compatible technology.