Probing the photo- and electro-catalytic degradation mechanism of methylene blue dye over ZIF-derived ZnO.

Due to the severe water pollution from effluent dyes, the need of the hour is to find a suitable dye degradation technology, and appropriate catalyst materials. Semiconducting ZnO was produced by pyrolysis of ZIF-8 template. The materials were well characterized with in situ and ex situ XRD and TGA, FE-SEM, HRTEM, UV-DRS, PL, and FRET. The results showed that upon calcination the body centered cubic ZIF-8 produces hexagonal primitive ZnO while retaining the truncated cubic shaped particles. The materials were screened for photo- and electro-catalytic oxidation of methylene blue. In both the different degradation technologies, ZnO synthesized from ZIF-8 outperformed the ZIF-8. The FRET dynamics showed significant spectral overlap of ZnO emission and the methylene blue absorption. It was found to be responsible for the better photocatalytic efficacy of ZnO samples than ZIF-8. The proposed reaction mechanism showed that the surface-bound reactive oxygen species produced either by light exposure or due to applied bias is key to dye degradation. The cytotoxicity of the untreated and ZnO and ZIF-8 treated dye over melanoma cells was evaluated, and it was found that the cytotoxicity of the degraded dye from ZIF-derived ZnO was less compared to that of ZIF-8 treated one.

Determination of band edges and their influences on photocatalytic reduction of nitrobenzene by bulk and exfoliated g-C3N4.

Thermally and chemically exfoliated metal-free semiconducting g-C3N4 are synthesized from bulk g-C3N4. Thorough characterization of the synthesized materials is performed with the help of XRD, FTIR, FE-SEM, PL, surface area analysis and DRS to probe differences in structural, morphological and optical properties between thermally and chemically exfoliated g-C3N4. The synthesized materials are exposed to light for photocatalytic reduction of nitrobenzene. The complete reduction reaction mechanism and product selectivity over the synthesized catalysts are studied in this report. The rate of reduction of nitrobenzene is found to be higher with thermally exfoliated g-C3N4, and the selectivity of aniline is found to be higher in the case of chemical exfoliated g-C3N4. The differences in the reactivity are explained in terms of structure, surface morphologies and band edge positions.

Enhanced Photoinduced Electrocatalytic Oxidation of Methanol Using Pt Nanoparticle-Decorated TiO2-Polyaniline Ternary Nanofibers.

Herein, perylene-3,4,9,10-tetracarboxylic acid-doped polyaniline (PTP) nanofibers with/without photoreactive anatase TiO2 (TiO2-PTP and PTP, respectively) have been successively synthesized and subsequently decorated by Pt nanoparticles (Pt NPs) to prepare Pt-PTP and Pt-TiO2-PTP composites. High-resolution transmission electron microscopy confirms the presence of ∼3 nm spherical-shaped Pt NPs on both the composites along with TiO2 on Pt-TiO2-PTP. Pt loading on the composites is deliberately kept similar to compare the methanol electro-oxidation in the two composites. The Pt nanocomposites along with the precursor polyanilines are characterized by optical characterization, X-ray diffraction study, X-ray fluorescence spectroscopy, and Raman spectroscopy. The ternary composite-modified (Pt-TiO2-PTP) electrode demonstrates high electrocatalytic performance for methanol oxidation reaction in acid medium than Pt-PTP and Pt-TiO2. The higher electrochemical surface area (1.7 times), high forward/backward current ratio, and the higher CO tolerance ability for Pt-TiO2-PTP make it a superior catalyst for methanol oxidation reaction in the electrochemical process than Pt-PTP. Moreover, the catalytic activity of Pt-TiO2-PTP is further enhanced significantly with light irradiation. The cooperative effects of photo- and electrocatalysis on methanol oxidation reaction in Pt-TiO2-PTP enhance the methanol oxidation catalytic activity approximately 1.3 times higher in light illumination than in dark. Therefore, the present work will be proficient to get a light-assisted sustainable approach for developing the methanol oxidation reaction activity of Pt NP-containing catalysts in direct methanol fuel cells.

Structure sensitive photocatalytic reduction of nitroarenes over TiO 2.

It is a subject of exploration whether the phase pure anatase or rutile TiO2 or the band alignment due to the heterojunctions in the two polymorphs of TiO2 plays the determining role in efficacy of a photocatalytic reaction. In this work, the phase pure anatase and rutile TiO2 have been explored for photocatalytic nitroarenes reduction to understand the role of surface structures and band alignment towards the reduction mechanism. The conduction band of synthesized anatase TiO2 has been found to be more populated with electrons of higher energy than that of synthesized rutile. This has given the anatase an edge towards photocatalytic reduction of nitroarenes over rutile TiO2. The other factors like adsorption of the reactants and the proton generation did not play any decisive role in catalytic efficacy.