Photocatalyst For Air Purification Research Articles

Atomically dispersed magnesium enhancing reactive oxygen species generation over g-C3N4 nanosheets for efficient photocatalytic NO removal

Photoinduced reactive oxygen species (ROSs)-involving nitrogen oxide (NOx) abatement offers a green way to mitigate environmental air pollution. Developing cost-effective photocatalysts remains challenging yet crucial. Herein, an atomically dispersed Mg-modified g-C3N4 nanosheet photocatalyst (xMg-CN) with excellent photoactivity is developed. The 1.0Mg-CN sample delivers a high NO removal rate of 52.3% under visible light irradiation within 30 min, far surpassing the Mg-free analog (CN, 41.2%). Moreover, a suppressed NO2 by-product discharge can be achieved. The introduction of Mg single atoms (SAs) alters the charge density distribution on the triazine ring plane of g-C3N4, inducing the formation of a built-in electric field, which improves the photoexcited charge carrier separation. Additionally, Mg SAs contribute to the adsorption and activation of O2 molecules, resulting in enhanced ROSs production, as evidenced by the experiments and theoretical simulations. The findings shed light on the role of SAs in designing highly efficient g-C3N4-based photocatalysts for air purification.

Dual function of ultra-laminated hydrotalcite in environmental remediation: Adsorption of water contaminant BP-4 and reutilization of the adsorption product for photocatalytic NOx air decontamination

UV filters are a class of emerging water pollutants used in cosmetics to protect the skin from ultraviolet radiation. This work appraises the uptake of benzophenone-4 (BP-4), widely used and highly soluble sunscreen agent, by its adsorption on hydrotalcite based compounds. The studied adsorbents were hydrotalcite Mg3Al-CO3 (HT), ultra-laminated hydrotalcite (UHT) prepared by “Aqueous Miscible Organic Solvent Treatment” and their calcined products (HT500 and UHT500, respectively). Adsorbents were characterised by different techniques such as XRD, TEM, FT-IR, BET, XRF and TGA. The most remarkable feature was the enhancement in the specific surface area (SSA) of the ultra-laminated hydrotalcite samples, UHT and UHT500 with values of 212 m2·g─1 and 247 m2·g─1, respectively. Adsorption capacities decreased from very high for UHT500 to low values for HT in order UHT500 > HT500 > UHT > HT. The results showed that not only the SSA values were relevant for adsorbing BP-4, but also other factors such as anionic exchange capacity (AEC) and surface charge. In addition, the adsorption product (UHT-BP4) was evaluated as a photocatalyst for air purification, exhibiting good efficiency for the removal of atmospheric pollutants such as NOx gases.

Synergistic effect of cyano defects and CaCO3 in graphitic carbon nitride nanosheets for efficient visible-light-driven photocatalytic NO removal.

Photo-oxidation with semiconductor photocatalysts provides a sustainable and green solution for NOx elimination. Nevertheless, the utilization of traditional photocatalysts in efficient and safe photocatalytic NOx removal is still a challenge due to the slow charge kinetic process and insufficient optical absorption. In this paper, we report a novel porous g-C3N4 nanosheet photocatalyst modified with cyano defects and CaCO3 (xCa-CN). The best performing sample (0.5Ca-CN) exhibits an enhanced photo-oxidation NO removal rate (51.18%) under visible light irradiation, largely surpassing the value of pristine g-C3N4 nanosheets (34.05%). Such an enhancement is mainly derived from an extended visible-light response, improved electron excitation and transfer, which are associated with the synergy of cyano defects and CaCO3, as evidenced by a series of spectroscopic analyses. More importantly, in-situ DRIFTS and density functional theory (DFT) results suggest that the introduction of cyano defects and CaCO3 enables control over NO adsorption and activation processes, making it possible to implement a preference pathway (NO → NO+ → NO3¯) and reduce the emission of toxic intermediate NO2. This work demonstrates the potential of integrating defect engineering and insulator modification to design highlyefficient g-C3N4-based photocatalysts for air purification.

Hollow TiO2/Poly (Vinyl Pyrrolidone) Fibers Obtained via Coaxial Electrospinning as Easy-to-Handle Photocatalysts for Effective Nitrogen Oxide Removal.

Herein, we present a method for fabricating hollow TiO2 microfibers from Ti (OBu)4/poly (vinyl pyrrolidone) sol-gel precursors and their effects on denitrification as a photocatalyst for air purification. Various sizes of hollow TiO2 fibers were developed using coaxial electrospinning by controlling the core flow rate from 0 to 3 mL h-1. At higher flow rates, the wall layer was thinner, and outer and core diameters were larger. These features are correlated with physical properties, including specific surface area, average pore diameter, and crystalline structure. The increase in the core flow rate from 0 to 3 mL h-1 leads to a corresponding increase in the specific surface area from 1.81 to 3.95 µm and a decrease in the average pore diameter from 28.9 to 11.1 nm. Furthermore, the increased core flow rate results in a high anatase and rutile phase content in the structure. Herein, hollow TiO2 was produced with an approximately equal content of anatase/rutile phases with few impurities. A flow rate of 3 mL h-1 resulted in the highest specific surface area of 51.28 m2 g-1 and smallest pore diameter size of ~11 nm, offering more active sites at the fiber surface for nitrogen oxide removal of up to 66.2% from the atmosphere.

Efficient photocatalytic oxidation of VOCs using ZnO@Au nanoparticles

The emission of toxic VOCs (Volatile Organic Compounds) in the environment causes serious problems and, if from one side there are directives to reduce this threat, from the other side there are stringent necessities for their removal. Several methods have been proposed to remove toxic VOCs, but little attention has been paid towards their photooxidation using materials with improved photodetection. For these reasons, we account here on the good photocatalytic performance of semiconducting ZnO@Au nanostructures that revealed to be excellent for both ultraviolet and visible light detection, thanks to the wide ZnO band gap and visible Au surface plasmon resonance, towards the photooxidation of some toxic Volatile Organic Compounds. In particular, we tested these peculiar materials for the removal of some common VOCs as toluene, ethanol and formaldehyde under solar light irradiation. The ZnO@Au showed excellent performance in the total oxidation of toluene (95% of conversion) and formaldehyde (85%) with the consequent formation of only CO2 and water as by-products. This good activity was also confirmed in the photooxidation of ethanol that allowed to obtain the 72% of CO2 selectivity. Furthermore, in all tests the catalysts showed a good stability after several consecutive runs. The efficient electronic communication between the gold core and the zinc oxide shell permitted to enhance the overall photodetection of the solar irradiation, improving also the charge carriers separation. The ZnO@Au nanostructures can be considering promising candidates as photocatalysts for air purification.