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.

Herein, perylene-3,4,9,10-tetracarboxylic acid-doped polyaniline (PTP) nanofibers with/without photoreactive anatase TiO 2 (TiO 2 –PTP and PTP, respectively) have been successively synthesized and subsequently decorated by Pt nanoparticles (Pt NPs) to prepare Pt–PTP and Pt–TiO 2 –PTP composites. High-resolution transmission electron microscopy confirms the presence of ∼3 nm spherical-shaped Pt NPs on both the composites along with TiO 2 on Pt–TiO 2 –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–TiO 2 –PTP) electrode demonstrates high electrocatalytic performance for methanol oxidation reaction in acid medium than Pt–PTP and Pt–TiO 2 . The higher electrochemical surface area (1.7 times), high forward/backward current ratio, and the higher CO tolerance ability for Pt–TiO 2 –PTP make it a superior catalyst for methanol oxidation reaction in the electrochemical process than Pt–PTP. Moreover, the catalytic activity of Pt–TiO 2 –PTP is further enhanced significantly with light irradiation. The cooperative effects of photo- and electrocatalysis on methanol oxidation reaction in Pt–TiO 2 –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.

Photocatalytic reduction of aqueous nitrate has been thoroughly studied over noble metals doped and pristine TiO 2 synthesized by a customized single step microwave assisted hydrothermal method. The synthesized catalysts are systematically characterized using XRD, Raman spectroscopy, FE-SEM, HR-TEM, XPS, diffuse reflectance spectroscopy, and PL measurements. The characterization reveals the successful synthesis of highly crystalline doped and undoped nano-TiO 2 . The photocatalytic rate of aqueous nitrate reduction over undoped TiO 2 is found to be higher than that of noble metal doped TiO 2 . Mechanistic studies of the photocatalytic reduction are carried out with the help of different hole (oxalic acid, and methanol) and electron (sodium persulfate) scavengers, which reveal that the photogenerated electrons are the primary agents toward efficient nitrate photoreduction. Detailed studies have revealed that the noble metal doping in TiO 2 helps in efficient photogeneration of H 2 compared to the undoped analogue, however, the in situ produced H 2 is found to be inefficient in reducing NO 3 − . The conduction band position from first principle calculations with respect to the nitrate and hydrogen reduction potentials derived from cyclic voltammetry provide insights to the electron transfer process in determining the reaction pathway.

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TiO2 synthesized by polymerizable sol–gel approach is used to demonstrate the photoreduction of Cr­(VI) in aqueous medium. Fe3O4 is chosen as the magnetically recoverable support, onto which, 10, 20, 30 and 50% of TiO2 have been dispersed following the polymerizable sol–gel approach. The synthesized materials are characterized using XRD, SEM, XPS, Raman spectroscopy, diffuse reflectance spectroscopy and BET surface area measurement. Different hole-scavengers (oxalic acid, ammonium oxalate and ethanol) and an electron scavenger (potassium periodate) have been studied to compare the efficiency of Cr­(VI) photoreduction in nitrogen as well as air atmosphere. With 5 mM oxalic acid as the hole-scavenger, the TiO2/Fe3O4 materials have demonstrated superior activity to the nonsupported bulk TiO2 toward Cr­(VI) photoreduction in aerobic atmosphere. Particularly, 30% TiO2/Fe3O4 has shown the highest Cr­(VI) photoreduction rate among the lot. The 30% TiO2/Fe3O4 catalyst has also demonstrated good recoverability as well as recyclability.