Tandem Photocatalysis Protocol for Hydrogen Generation/Olefin Hydrogenation Using Pd-g-C₃N₄-Imine/TiO₂ Nanoparticles

Abstract

An unprecedented visible-light-driven photocatalytic system consisting of Pd nanoparticles stabilized on g-C 3 N 4imine-functionalized TiO 2 nanoparticles was discovered for photoassisted hydrogen generation followed by olefin hydrogenation under mild conditions. The structural integrity of the assynthesized photocatalyst was corroborated by Fourier transform infrared spectroscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-diffuse reflectance spectroscopy, Brunauer−Emmett−Teller measurements, and thermogravimetric analysis (TGA). Transmission electron microscopy and high-resolution scanning electron microscopy revealed the nanoscopic nature of the catalyst. The photocatalyst promoted several different transformations in a onepot reaction sequence: hydrogen evolution through photocatalytic acceptorless formation of benzimidazoles as important therapeutic agents followed by visible-light-driven photocatalytic reduction of olefins with a high hydrogen utilization efficiency of up to 92% under mild conditions. A significant volume of H 2 was produced under blue light-emitting diode (LED) irradiation during the selective formation of benzimidazole, while the selectivity reduced significantly under a Xe lamp or in the dark. The in situgenerated H 2 could be activated by the as-prepared Pd-C 3 N 4 -imine/TiO 2 photocatalyst to effectively hydrogenate olefins under mild conditions at appropriate time exposed to blue LED irradiation. The light-dependent photocatalytic performance of the title catalyst was assessed using action spectra by calculating the apparent quantum efficiency (AQE), which exhibited the maximum AQEs at 410 and 550 nm, at which the highest performance for styrene hydrogenation was obtained. The improved photoredox activity of the title nanohybrid could be caused by the synergistic effects of the heterojunction of carbon nitride-Pd on TiO 2 nanoparticles evidenced by photoluminescence spectra and catalytic reactions. The catalyst proved to be air-stable, robust, recyclable, and very active in the absence of any undesirable additives and reducing agents. Thus, this work presents a new protocol for improving the photocatalytic properties of semiconducting materials for various photocatalytic applications under environmentally friendly conditions.

Enhanced Visible-Light-Induced Photocatalytic Activity in M(III)Salophen-Decorated TiO2 Nanoparticles for Heterogeneous Degradation of Organic Dyes

“…The main signal with the largest area centered at a binding energy of 198.65 eV demonstrates inorganic chlorine (BE < 199 eV) from a chloride salt with Fe 3+ . , Si 2p exhibited three signals at binding energies of 98.6, 101.75, and 102.8 eV, indicating the covalent bonding of Si in Si–C, Si–O, and Si–O–Ti, respectively . Main signals of Ti 2p are observed at binding energies of 458.25 eV (2p 3/2 ) and 463.8 eV (2p 1/2 ) for TiO 2 …”

TiO2nanoparticles decorated with Co-Schiff base-g-C3N4as an efficient photocatalyst for one-pot visible light-assisted synthesis of benzimidazoles

“…At the first step of this investigation, TiO 2 nanoparticles and g-C 3 N 4 (ref. 47) were prepared by following the reported procedures with minor modifications. Then, g-C 3 N 4 /Imine organosilicon compound was synthesized with the condensation of the –NH 2 group of g-C 3 N 4 with organosilicon aldehyde, which was prepared by our group.…”

“…Note: see the step-by-step preparation of the g-C 3 N 4 -imine/TiO 2 nanohybrid in the ESI. † 47 2.1 Preparation of the Co-g-C 3 N 4 -imine/TiO 2 nanohybrid First, 0.1 g TiO 2 nanoparticles were gradually added to 0.1 g Schiff base of carbon nitride in ethanol at 60 C under ultrasonic agitation. Then, the as-obtained mixture was reuxed for 8 h. Thus, the product was centrifuged and washed with ethanol.…”

g-C3N4 Derived Materials for Photocatalytic Hydrogen Production: A Mini Review on Design Strategies

“…Among the numerous materials, inorganic semiconductor materials are of low cost compared with rare metal catalysts [5]. The g-C 3 N 4 polymer can induce visible light and its unique electronic structure and adaptive capacity to adjust the band structure has attracted wide interest [6,7]. Moreover, the easy acquaintance from nature, no toxicity and strong stability of the C and N elements make them stand out.…”