Papers by Keyword: Photocatalysis

Abstract: The incorporation of quasi-atomic Ni (OH)₂ clusters onto graphitic C₃N₄ (gCN) remarkably enhances the photocatalytic production of hydrogen peroxide (H₂O₂) and benzaldehyde (BAL) from benzyl alcohol (BA) in water under visible light at 440 nm. Upon loading Ni (OH)₂, H₂O₂ production reaches 306 µmol g⁻¹ h⁻¹ and BAL production reaches 270 µmol L⁻¹ h⁻¹. The high photocatalytic performance is attributed to the formation of ultrasmall clusters of Ni (OH)₂, which reduce recombination by trapping holes, thereby increasing the activity (BA conversion). Efficient hole transfer to BA is also facilitated, enhancing selectivity (BAL selectivity). Upon the addition of Ni (OH)₂, the steady-state electron population photoexcited by visible light increases 5.5-fold. The proposed modification of gCN with Ni achieves nearly 100% efficiency in both activity and selectivity to produce H₂O₂, while also generating BAL, a value-added product. This demonstrates its potential for sustainable chemical transformations using visible light and water as a green solvent.

Abstract: This review highlights the recent advancements in the synthesis and application of magnetic spinel ferrites (SFs) for wastewater treatment, focusing on their photocatalytic and adsorptive properties. SF nanoparticles, with unique characteristics such as high surface area, tunable magnetic properties, and chemical stability, offer efficient pollutant degradation and recovery via magnetic separation. Various synthesis techniques, including sol-gel, hydrothermal, and solution combustion, have been explored to enhance their morphology, porosity, and catalytic efficiency. SFs demonstrate exceptional performance in degrading organic pollutants, dyes, and pharmaceutical contaminants under visible light, leveraging their photocatalytic and adsorption mechanisms. The effectiveness is further increased by combining SFs with advanced materials including g-C3N4 and r-GO. A worldwide sustainable water treatment issue makes this study significant because SFs present scalable environmentally friendly solutions that have revolutionary potential.

Abstract: Chemical synthesis of nanocomposite particles based on titanium dioxide modified with iron and gold was carried out. It was shown that, depending on the mass content of the doping species, the phase transformation of titanium hydroxide at T = 700 °C proceeds with the formation of either anatase (2 wt.%) or anatase and rutile (8 wt.%). The doping species form a hematite phase and gold clusters on the metal-oxide surface. A weakly crystalline anatase obtained by the transformation of metatitanic acid (MTA), with a particle size of 8 nm and a sulfur content of 0.036%, was selected as the co-catalyst. The anatase co-catalyst exhibits photocatalytic activity in the destruction of organic dyes. Its introduction into the TiO₂&Fe₂O₃&Au nanocomposite suspension promotes the catalytic degradation of cationic and anionic dyes at temperatures ranging from 35 to 60 °C. It was observed that the degradation degree of the solutions after 150 min of catalytic process is the following: Methyl Orange (MO) – 72 %, Methylene Blue (MB) – 71.5 %, Rhodamine B (RhB) – 63.5 %, and Orange G (OG) – 47 %. The reaction rate constant depends on the composition of the dye, varying from 6.5·10^-4 min^-1 for OG to 2.56·10^-3 min^-1 for MB. The prospect of creating heterostructures based on TiO₂ modified with hematite and gold, and their further adaptation for photocatalytic hydrogen production, is considered.

Abstract: In this work, photoelectron nanocomposites of TiO₂&CeO₂&Ag were synthesized by a co-deposition method using TTIP (Titanium TetraIsoPropoxide) and water solutions of Ce(NO₃)₃ and AgNO₃. Heat treatment of the precipitates at 600°C led to the formation of an anatase phase with the primary particles’ size of 14.1–15.2 nm. Molecules of Malachite green and Methylene blue are intensively adsorbed on the surface of nanocomposites. TiO₂&CeO₂&Ag nanocomposites show high photocatalytic activity to cationic dyes and weak – to anionic ones. The photocatalytic decomposition of cationic dyes is accompanied by a hypsochromic shift of chromophoric bands. Only the chromophoric part of the dye molecules is destroyed by temperature (catalytic process). Nanocomposites based on anatase containing 1–2 wt.% of Ag and Ce show the highest photocatalytic activity for the destruction of organic dyes.

Abstract: Tin oxide thin films were synthesized on FTO substrates by the Radio Frequency sputtering technique in aO₂/Ar mixture atmosphere. X-ray diffraction patterns revealed the formation of tetragonal structure of SnO₂ films, with a crystallite size that increases from 8.3 to 10.3 nm by increasingthe oxygen percentage from 5% to 15%, then decreases again at 30%oxygen. SEM images reveal homogeneous, smooth, non-porous and crack-free surfaces in all films. EDX spectra confirm the increasing O/Sn ratio for high oxygen percentages. Optical transmittance is observed toincrease with increasing the oxygen percentagewith an energyband gap ranging between 3.78 and 3.91 eV. Mott-Schottky characterization shows higher charge carrier concentration in the film synthesized with 10% O₂. This film exhibits, afterwards, the highest efficiency in terms of degradation of in a UV photoreactor.

Abstract: Photocatalytic reduction of carbon dioxide (CO₂) to solar fuel is a potential approach to overcome the problem of high CO₂ concentrations; however, the process still faces enormous challenges, such as low light absorption efficiency and high carrier recombination rates. Herein, Fe-doped carbon dots were prepared by a one-step hydrothermal method using sodium citrate, ethylenediamine, and FeCl₃·6H₂O as raw materials. The performances of the resulting materials toward the photocatalytic reduction of CO₂ were investigated and the results showed that Fe doping can regulate the energy band structure of CDs. However, the conduction band potential of Fe-carbon dots displayed no obvious influence except in terms of band gap. Moreover, Fe doping reduced the recombination rate of photo-generated carriers in CDs, increased the mobility of photo-generated carriers, and declined the resistance during the migration of photo-generated electrons. The photocatalytic reduction performances of CO₂ illustrated conversion yield of CO₂ to CH₃OH reaching 289.81 μmol·g (cat)^-1·h^-1 using Fe-CDs-13.0 catalyst, a value 2.36-fold higher than that of CDs. We found that Fe-CDs were synthesized by modulating the energy band structure of CDs. Fe-CDs improve visible light utilization and apply them to the photocatalytic reduction of CO₂.

Abstract: This study involves the photocatalytic degradation of methylene blue (MB) under visible light using reticulated stainless steel that is coated with copper-doped TiO₂. Steel meshes of three different grades are used in the experiment: 50 mesh, 120 mesh and 400 mesh. The coating process coats an average of 0.3 mg/cm² of Cu–TiO₂ on the 50 mesh and the 120 mesh and 0.2 mg/cm² on the 400 mesh. SEM and XRD characterization show that the roughness of the mesh wire surface increases as the amount of coating is increased. All three types of mesh remove approximately 50% of MB, when coated with 1 mg/cm² of CuO-TiO₂. When the amount of coating is increased to 2.5 mg/cm², the order for the photocatalytic degradation of MB for the three meshes is 120 mesh (93%) > 400 mesh (91%) > 50 mesh (86%). However, when the amount of coating is further increased to 2.5 mg/cm², there is no significant difference between the three mesh groups, in terms of MB residue. The study demonstrates that the photocatalytic efficiency is affected by the surface area and thickness of the membrane that forms over the mesh openings.

Abstract: Self-assembled hierarchical Bi₂WO₆ microsphere was synthesized via a facile hydrothermal method. The fabricated Bi₂WO₆ exhibited up to 85.3% Cr(VI) reduction efficacy which was much greater than that of commercially available P25 TiO₂ nanoparticles. Furthermore, Bi₂WO₆ microsphere also produced about 1.5-fold greater H₂ quantity in water splitting compared to P25 TiO₂. The photocatalytic enhancement of Bi₂WO₆ microsphere was ascribed to its unique hierarchical porous architecture and large surface area which can improve the charge carrier quantities for redox reactions. The present study could be useful for fabricating Bi₂WO₆ photocatalyst with improved performance in environmental remediation and renewable energy applications.

Abstract: Photocatalysis properties enhanced by metal and organic polymer has been received more interest because of their ability to directly or indirectly degrade pollutants. The effect of PDA (polydopamine) and Ag nanoparticles on the different phases of ZnO to degrade organic dyes under visible and UV-vis light was investigated. ZnO@PDA, ZnO-Ag, and ZnO-Ag@PDA nanoparticles were synthesized. It’s shown that Ag particles with sizes of less than 20 nm were deposited evenly on the ZnO. There were a few changes in the structure of ZnO@PDA or ZnO-Ag @PDA. When the ZnO was coated by PDA, the photocatalytic activity could be enhanced. The photocatalytic activity under UV-vis and visible light of the ZnO@PDA were effectively improved. The degradation rate of ZnO-Ag@PDA was 97.9% under UV-vis light for 20 mins, which was 16.1% higher than that of ZnO. The photocatalytic activity of ZnO-Ag@PDA reached the maximum after polymerizing for 2 hours. The photocatalytic efficiency of ZnO-Ag@PDA-2h under UV-vis for 30 minutes can reach higher than 99.01%. The photocatalytic performance decreased rapidly with the increasing cycles. When the number of cycles was 5, the degradation rate was 65.84%. Afterward, the degradation rate changed small and became stable.

Abstract: The photoactive nanocomposites TiO₂/Sn⁴⁺ with various ratios of Sn⁴⁺ were prepared by a sol-gel method. Their morphology and crystal structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The effect of various parameters such as amount of doped Sn⁴⁺ ions, catalyst loading, initial pollutant concentration, pH value, H₂O₂ concentration on photocatalytic degradation performance were analyzed and optimized. The optimal experimental conditions obtained through orthogonal experiments that highest value was obtained at 3%-Sn⁴⁺ doping amount, catalyst dosage 1.5 g/L, initial chemical oxygen demand(COD) concentration 600 mg/L, initial ammonia nitrogen(NH₄⁺-N) concentration 50 mg/L, H₂O₂ 3%, and pH = 8. The photocatalytic degradation rates of NH₄⁺-N and COD reached 87.54% and 75.32%, respectively.