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Graphitic carbon nitride (g-C3N4), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C3N4 were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C3N4 and exfoliated g-C3N4 was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C3N4 synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH4 and CO resulting from the reduction of CO2 were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel chemically mixed sol gel TiO 2 and graphene composite catalyst. • Catalyst with dual NO 2 sensing and abatement capabilities. • Conductometric sensing of NO 2 in the range 70–1750 ppb. • Photocatalytic abatement of NO 2 under simulated sunlight radiation 280–780 nm. Abstract Human exposure to volatile organic compounds and NO 2 can lead to health problems, therefore strategies to mitigate against the risks are required. Abatement and sensing are approaches which could both neutralise and monitor these species thus providing a safer environment and warning occupants of harmful levels. This paper presents pure TiO 2 and TiO 2 /graphene hybrids synthesized through a sol-gel route. Electron optical, helium ion microscopy, X-ray diffraction and spectroscopic methods have been applied to elucidate the physical and chemical behaviour. NO 2 sensing properties of TiO 2 /graphene hybrids formed by the addition of graphene to the reaction vessel prior to initiating the sol gel reaction followed by annealing (GTiO 2 S), and an alternative manufacturing method involving the addition of graphene to TiO 2 nanoparticles which had already been annealed (GTiO 2 M) were compared and evaluated. A conductometric sensor based on TiO 2 /graphene prepared using material GTiO 2 S showed a higher response to NO 2 compared to sensors based on pure TiO 2 and TiO 2 /graphene prepared with material GTiO 2 M. Under UV irradiation generated by a low power LED, the sensor showed a remarkably enhanced response to 1750 ppb NO 2 , about double the response in the dark, and a limit of detection of about 50 ppb of NO 2 (Signal/Noise = 3). Photocatalytic tests to assess the degradation of NO x showed that TiO 2 /graphene hybrids using material GTiO 2 S were the most active amongst the whole series of TiO 2 -based materials. Our data highlights the unique characteristics of material GTiO 2 S TiO 2 /graphene and the suitability for multi-purpose applications in the field of environmental monitoring and remediation. The capability of the material for both sensing and abatement of NO x could be exploited to offer a safer environment through providing a warning of the presence of NO x whilst also reducing levels. [ABSTRACT FROM AUTHOR]

The development of highly efficient photocatalyst under visible light still a challenge. Herein we present band gap modification of NH 2 -MIL-125 by encirclement with suitable semiconductor that possesses a narrow band gap Ag 3 PO 4 nanoparticles (NPs). The band gap of NH 2 -MIL-125 was decreased from 2.51 to 2.39 eV, making them potential candidates for photocatalytic applications. Our prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). TEM characterizations indicated that NH 2 -MIL-125 MOFs are coated with Ag 3 PO 4 NPs. The photocatalytic activity (PCA) was evaluated in the liquid-solid phase, by monitoring the degradation of an organic dye (methylene blue (MB) and rhodamine-B (RhB)) under visible-light irradiation. Furthermore, the Ag 3 PO 4 @NH 2 -MIL-125 nanocomposites shown themselves to be the most active with the reaction rate being 39 and 35 times higher than the well known Degussa P25 TiO 2 toward photocatalytic degradation of MB and RhB. [ABSTRACT FROM AUTHOR]

This article describes the synthesis of tungsten doped (W–TiO 2) nanoparticles and their incorporation into a coating to improve the air quality inside buildings. W–TiO 2 was prepared using a sol-gel synthesis route incorporating 1%, 2.5% and 3% tungsten in TiO 2. Coatings containing the nanoparticles were produced using a water/alcohol liquid phase containing a polyurethane binder and applied to the surface of medium density fibreboard (MDF). Photocatalytic activity of unbound nanoparticles was studied using methylene blue degradation to evaluate liquid/solid interface reactions and NO x degradation to study gas/solid interfacial reactions. The coatings containing the nanoparticles were applied onto the surface of MDF and evaluated using Ink Intelligent indicator dyes. In the tests photocatalytic activity under visible light of all W–TiO 2 concentrations exhibited a higher activity compared to the commercially available Degussa P25. This paper has demonstrated for the first time that polyurethane W–TiO 2 coatings can be effectively applied to MDF and exhibit activity in visible light. • Sol gel synthesis of W–TiO 2 nanoparticles doped with 1%, 2.5% and 3% tungsten. 81. • Evaluation of W–TiO 2 in liquid phase using methylene blue and gas phase using NOx. 85. • Enhanced photocatalytic performance of W–TiO 2 in the visible light spectrum. 79. • Development of polyurethane-based coating for medium density fiber board. 83. • Evaluation of polyurethane W–TiO 2 coating using ink intelligent dyes. 72. [ABSTRACT FROM AUTHOR]

The growing world energy consumption, with reliance on conventional energy sources and the associated environmental pollution, are considered the most serious threats faced by mankind. Heterogeneous photocatalysis has become one of the most frequently investigated technologies, due to its dual functionality, i.e., environmental remediation and converting solar energy into chemical energy, especially molecular hydrogen. H2 burns cleanly and has the highest gravimetric gross calorific value among all fuels. However, the use of a suitable electron donor, in what so-called "photocatalytic reforming", is required to achieve acceptable efficiency. This oxidation half-reaction can be exploited to oxidize the dissolved organic pollutants, thus, simultaneously improving the water quality. Such pollutants would replace other potentially costly electron donors, achieving the dual-functionality purpose. Since the aromatic compounds are widely spread in the environment, they are considered attractive targets to apply this technology. In this review, different aspects are highlighted, including the employing of different polymorphs of pristine titanium dioxide as photocatalysts in the photocatalytic processes, also improving the photocatalytic activity of TiO2 by loading different types of metal co-catalysts, especially platinum nanoparticles, and comparing the effect of various loading methods of such metal co-catalysts. Finally, the photocatalytic reforming of aromatic compounds employing TiO2-based semiconductors is presented. [ABSTRACT FROM AUTHOR]

This article reports a novel photocatalytic lime render for indoor and outdoor air quality improvement that is composed of a lime binder and doped TiO2 (KRONOClean 7000®) nanoparticles. These nanoparticles were distributed throughout the bulk of the finishing render, instead of as a thin coating, thus ensuring the durability of the photocatalytic properties upon superficial damage. The physical properties of these renders were not affected by the addition of nanoparticles except in the case of surface area, which increased significantly. In terms of their photocatalytic activity, these novel lime renders were shown to degrade up to 12% NOx under UV light and up to 11% formaldehyde under visible light. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C3N4 were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C3N4 and exfoliated g-C3N4 was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C3N4 synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH4 and CO resulting from the reduction of CO2 were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]