Monometallic nanoparticles decorated and rare earth ions doped KTaO3/K2Ta2O6 photocatalysts with enhanced pollutant decomposition and improved H2 generation

Current trends on dry photocatalytic oxidation technology for BTX removal: Viable light sources and highly efficient photocatalysts

One of the main gaseous pollutants released by chemical production industries are benzene, toluene and xylene (BTX). These dangerous gases require immediate technology to combat them, as they put the health of living organisms at risk. The development of heterogeneous photocatalytic oxidation technology offers several viewpoints, particularly in gaseous-phase decontamination without an additional supply of oxidants in air at atmospheric pressure. However, difficulties such as low quantum efficiency, ability to absorb visible light, affinity towards CO2 and H2O synthesis, and low stability continue to limit its practical use. This review presents recent advances in dry-phase heterogeneous photodegradation as an advanced technology for the practical removal of BTX molecules. This review also examines the impact of low-cost light sources, the roles of the active sites of photocatalysts, and the feasible concentration range of BTX molecules. Numerous studies have demonstrated a significant improvement in the efficiency of the photodegradation of volatile organic compounds by enhancing the photocatalytic reactor system and other factors, such as humidity, temperature, and flow rate. The mechanism for BTX photodegradation based on density functional theory (DFT), electron paramagnetic resonance (EPR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) investigations is also discussed. Finally, the present research complications and anticipated future developments in the field of heterogeneous photocatalytic oxidation technology are discussed.

Surfactant-Modified CdS/CdCO3 Composite Photocatalyst Morphology Enhances Visible-Light-Driven Cr(VI) Reduction Performance

The surfactant modification of catalyst morphology is considered as an effective method to improve photocatalytic performance. In this work, the visible-light-driven composite photocatalyst was obtained by growing CdS nanoparticles in the cubic crystal structure of CdCO₃, which, after surfactant modification, led to the formation of CdCO₃ elliptical spheres. This reasonable composite-structure-modification design effectively increased the specific surface area, fully exposing the catalytic-activity check point. Cd²⁺ from CdCO₃ can enter the CdS crystal structure to generate lattice distortion and form hole traps, which productively promoted the separation and transfer of CdS photogenerated electron-hole pairs. The prepared 5-CdS/CdCO₃@SDS exhibited excellent Cr(VI) photocatalytic activity with a reduction efficiency of 86.9% within 30 min, and the reduction rate was 0.0675 min^-1, which was 15.57 and 14.46 times that of CdS and CdCO₃, respectively. Finally, the main active substances during the reduction process, the photogenerated charge transfer pathways related to heterojunctions and the catalytic mechanism were proposed and analyzed.

Structural, electronic, optical and photocatalytic properties of KTaO3 with NiO cocatalyst modification

Density functional theory calculations reveal that NiO serves as an oxidation cocatalyst to form type-II band alignment with KTaO3, which suppresses the recombination of photoinduced carriers and enhances the photocatalytic activity of KTaO3.

Hydrothermal preparation of novel rGO-KTaO3 nanocubes with enhanced visible light photocatalytic activity

In this study, nanocubes KTaO₃-reduced graphene oxide (rGO-KTaO₃) photocatalysts were synthesized by a facile hydrothermal method. Different technical methods were carried out to characterize the as-prepared compounds. UV-Vis spectra show that the absorption sideband of the complexes red-shift to visible light region, which enhances the light utilization. Meanwhile, X-ray photoelectron spectroscopy (XPS) reveals that the graphene oxide (GO) in the composite has been partially reduced, leading to more effective electron transport and thus improving the photocatalytic efficiency. Furthermore, photocatalytic degradation efficiency of Methylene blue (MB) and Rhodamine B (RhB) in the presence of rGO-KTaO₃ reaches 96% and 98%, which is 10 times of that of KTaO₃. The synthesized rGO-KTaO₃ has good photocatalytic properties. Moreover, the stability of this photocatalyst is particularly excellent. The detailed mechanism of photocatalysis has been carefully discussed in the article.

Pyrochlore oxides as visible light-responsive photocatalysts

This perspective describes the use of pyrochlore oxides in photocatalysis with focus on the strategies to enhance their activity.

Hyper oxygen incorporation in CeF3: a new intermediate-band photocatalyst for antibiotic degradation under visible/NIR light

Intermediate-band semiconductors perform functions similar to natural photosynthesis by combining two photons to achieve a higher electron excitation. In this study, a strategy was developed to prepare a high oxygen-doped CeF₃ (CeF₃-O) nanomaterial that exhibits photocatalytic activity under visible/NIR light for the first time. The homogeneous doping oxygen atoms were verified to efficiently modify the band structure of CeF₃. DFT calculation predicted the formation of an intermediate band within CeF₃ upon homogeneous doping of O at interstitial sites. The interaction between F and O atoms generates an intermediate band, which divides the total bandgap of CeF₃-O into two sub-bandgaps at about 1.7 eV and 2.9 eV, enabling CeF₃-O photocatalysis under visible light and NIR light. Reflectance spectra evidenced that the same bandgaps exist. The photocatalytic activities of CeF₃-O were tested by wavelength-controlled light. The rate constants of TC-HCl photodegrading under visible/NIR light are 12.85 × 10⁻³ min⁻¹ and 1.28 × 10⁻³ min⁻¹, respectively. The two-step electron transfer was also obviously confirmed in visible-light photocatalysis. In conclusion, the high oxygen doping builds a more applicable band structure of CeF₃-O for photocatalytic performance, charge transfer and special light response for visible/NIR light.

Hyper doping O acts as a nonradiative center and generates an intermediate band with F atoms, exhibiting efficient photocatalysis activities under visible/NIR light.

Complementary behavior of doping and loading in Ag/C-ZnTa2O6 for efficient visible-light photocatalytic redox towards broad wastewater remediation

This work reports on the simple fabrication of a silver loaded and carbon doped zinc tantalate (Ag/C-ZnTa₂O₆) photocatalyst with visible light photocatalytic activity toward broad wastewater remediation, including high photo-reduction of Cr(vi) (98.4% in 210 min), excellent photo-oxidation of tetracycline hydrochloride (94.7% in 210 min), and superior photo-degradation of multiple dyes (>99.0% within 210 min). The optimal photocatalytic performance of Ag/C-ZnTa₂O₆ is mainly due to the excellent visible light absorption capacity and superior electron-hole separation efficiency, which is ascribed to the complementary behavior between carbon doping and silver loading. Particularly, the generation of defects due to C-doping is greatly inhibited by Ag-loading, and the SPR effect of Ag nanoparticles is enhanced due to the obstruction of Ag⁺ by C doping.

Rare-earth-containing perovskite nanomaterials: design, synthesis, properties and applications

As star material, perovskites have been widely used in the fields of optics, photovoltaics, electronics, magnetics, catalysis, sensing, etc. However, some inherent shortcomings, such as low efficiency (power conversion efficiency, external quantum efficiency, etc.) and poor stability (against water, oxygen, ultraviolet light, etc.), limit their practical applications. Downsizing the materials into nanostructures and incorporating rare earth (RE) ions are effective means to improve their properties and broaden their applications. This review will systematically summarize the key points in the design, synthesis, property improvements and application expansion of RE-containing (including both RE-based and RE-doped) halide and oxide perovskite nanomaterials (PNMs). The critical factors of incorporating RE elements into different perovskite structures and the rational design of functional materials will be discussed in detail. The advantages and disadvantages of different synthesis methods for PNMs will be reviewed. This paper will also summarize some practical experiences in selecting suitable RE elements and designing multi-functional materials according to the mechanisms and principles of REs promoting the properties of perovskites. At the end of this review, we will provide an outlook on the opportunities and challenges of RE-containing PNMs in various fields.