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Heterojunctions of small CuO nanoclusters (synthesized by radiolysis) with TiO2 (commercial P25) induced a photocatalytic activity under visible light irradiation in a wide range of wavelengths due to the narrow bandgap of CuO nanoclusters of around 1.7 eV. The optical, chemical, and electrical properties of these composite nanomaterials were studied. The photocatalytic properties of bare and modified TiO2–P25 were studied for water purification (photooxidation of organic compounds such as phenol and 2-propanol) and for hydrogen generation under visible light irradiation. Time resolved microwave conductivity signals showed activation of TiO2 under visible light, proving the injection of electrons from CuO nanoclusters to the conduction band of TiO2–P25. The modified materials showed high photocatalytic activity under visible light. The important role of charge-carriers was demonstrated for both photoreduction and photooxidation reactions. [ABSTRACT FROM AUTHOR]

Graphdiyne (GDY), which features a highly π‐conjugated structure, direct bandgap, and high charge carrier mobility, presents the major requirements for photocatalysis. Up to now, all photocatalytic studies are performed without paying too much attention on the GDY bandgap (1.1 eV at the G0W0 many‐body theory level). Such a narrow bandgap is not suitable for the band alignment between GDY and other semiconductors, making it difficult to achieve efficient photogenerated charge carrier separation. Herein, for the first time, it is demonstrated that tuning the electronic bandgap of GDY via H‐substitution (H‐GDY) promotes interfacial charge separation and improves photocatalytic H2 evolution. The H‐GDY exhibits an increased bandgap energy (≈2.5 eV) and exploitable conduction band minimum and valence band maximum edges. As a representative semiconductor, TiO2 is hybridized with both H‐GDY and GDY to fabricate a heterojunction. Compared to the GDY/TiO2, the H‐GDY/TiO2 heterojunction leads to a remarkable enhancement of the photocatalytic H2 generation by 1.35 times under UV–visible illumination (6200 µmol h−1 g−1) and four times under visible light (670 µmol h−1 g−1). Such enhancement is attributed to the suitable band alignment between H‐GDY and TiO2, which efficiently promotes the photogenerated electron and hole separation, as supported by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Keywords: charge carrier; density functional theory (DFT); electronic bandgap; graphdiyne; photocatalysis EN charge carrier density functional theory (DFT) electronic bandgap graphdiyne photocatalysis 1 1 1 07/19/21 20210701 NES 210701 Tuning the electronic bandgap of graphdiyne is an efficient way to construct a type II heterojunction for photocatalysis. Photocatalysis: Tuning the Electronic Bandgap of Graphdiyne by H-Substitution to Promote Interfacial Charge Carrier Separation for Enhanced Photocatalytic Hydrogen Production (Adv. Funct. Charge carrier, density functional theory (DFT), electronic bandgap, graphdiyne, photocatalysis. [Extracted from the article]

Coupling metal-organic frameworks (MOFs) with inorganic semiconductors has been successfully tested in a variety of photocatalytic reactions. In this work we present the synthesis of TiO2/HKUST-1 composites by grinding, solvothermal, and chemical methods, using different TiO2 loadings. These composites were used as photocatalysts for hydrogen production by the photoreforming of a glycerol-water mixture under simulated solar light. Several characterization techniques were employed, including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), infrared spectroscopy (FTIR), and time-resolved microwave conductivity (TRMC). A synergetic effect was observed with all TiO2/HKUST-1 composites (mass ratio TiO2/MOF 1:1), which presented higher photocatalytic activity than that of individual components. These results were explained in terms of an inhibition of the charge carrier (hole-electron) recombination reaction after photoexcitation, favoring the electron transfer from TiO2 to the MOF and creating reversible Cu1+/Cu0 entities useful for hydrogen production. [ABSTRACT FROM AUTHOR]