Strategies for enhancing performance of perovskite bismuth ferrite photocatalysts (BiFeO3): A comprehensive review.

Organic pollutants pose a significant threat to water safety, and their degradation is of paramount importance. Photocatalytic technology has emerged as a promising approach for environmental remediation, and Bismuth ferrite (BiFeO3) has been shown to exhibit remarkable potential for photocatalytic degradation of water pollutants, with its excellent crystal structure properties and visible light photocatalytic activity. This review presents an overview of the crystal properties and photocatalytic mechanism of perovskite bismuth ferrite (BiFeO3), as well as a summary of various strategies for enhancing its efficiency in photocatalytic degradation of organic pollutants. These strategies include pure phase preparation, microscopic modulation, composite modification of BiFeO3, and the integration of Fenton-like reactions and external field-assisted methods to improve its photocatalytic performance. The review emphasizes the impact of each strategy on photocatalytic enhancement. By providing comprehensive strategies for improving the efficiency of BiFeO3 photocatalysis, this review inspires new insights for efficient degradation of organic pollutants using BiFeO3 photocatalysis and contributes to the development of photocatalysis in environmental remediation.

Construction of Ternary Bismuth-Based Heterojunction by Using (BiO)2 CO3 as Electron Bridge for Highly Efficient Degradation of Phenol.

Inspired by nature, it has been considered an effective approach to design artificial photosynthetic system by fabricating Z-scheme photocatalysts to eliminate environmental issues and alleviate the global energy crisis. However, the development of low cost, environment-friendly, and high-efficient photocatalysts by utilizing solar energy still confronts huge challenge. Herein, we constructed a Bi2 O3 /(BiO)2 CO3 /Bi2 MoO6 ternary heterojunction via a facile solvothermal method and calcination approach and used it as a photocatalyst for the degradation of phenol. The optimized Bi2 O3 /(BiO)2 CO3 /Bi2 MoO6 heterojunction delivers a considerable activity for phenol photodegradation with an impressive removal efficiency of 98.8 % and about total organic carbon (TOC) of 68 % within 180 min under visible-light irradiation. The excellent photocatalytic activity was ascribed to the formation of a Z-scheme heterojunction, more importantly, the presence of (BiO)2 CO3 as an electron bridge greatly shortens the migration distance of photogenerated electron from ECB of Bi2 O3 to EVB of Bi2 MoO6 , thus prolonging the lifetime of photogenerated electrons, which is verified by trapping experiments, electron spin-resonance spectroscopy (ESR) results, and density functional theory (DFT) calculations. This work provides a potential strategy to fabricate highly efficient Bi-based Z-scheme photocatalysts with wide application prospects in solar-to-fuel conversion and environmental protection.

Water quality characteristics and evaluation of Qilian Mountain National Park section in Heihe River Basin based on water quality indices and 3D fluorescence technology.

The water quality of the Heihe River Basin affects the life quality and health of tens of thousands of residents along it. However, there are relatively few studies that evaluate its water quality. In this study, we used principal component analysis (PCA), an improved comprehensive water quality index (WQI), and three-dimensional (3D) fluorescence technology to identify pollutants and evaluate water quality at nine monitoring sites in the Qilian Mountain National Park in Heihe River Basin. PCA was applied to concentrate the water quality indices into nine items. The analysis shows that the water quality in the study area is mainly polluted by organic matter, nitrogen, and phosphorus. According to the revised WQI model, the water quality of the study area is from moderate to good, while the water quality of Qinghai section is worse than that of Gansu section. According to the 3D fluorescence spectrum analysis of the monitoring sites, the organic pollution of water comes from vegetation decay, animal feces, and some human activities. This study can not only provide support and basis for water environment protection and management in the Heihe River Basin, but also promote the healthy development of the water environment in the Qilian Mountains.

In situ fabrication of Bi2MoO6/Bi2MoO6-x homojunction photocatalyst for simultaneous photocatalytic phenol degradation and Cr(VI) reduction.

In this work, we designed a novel Bi2MoO6/Bi2MoO6-x homojunction photocatalyst and successfully fabricated by a facile solvothermal-calcination approach. Experimental characterizations indicated that the formation of Bi2MoO6/Bi2MoO6-x homojunction was caused by controlling oxygen vacancies formation. Such Bi2MoO6/Bi2MoO6-x homojunction exhibits about 240 times higher photocatalytic activity towards phenol degradation as compared with pure Bi2MoO6 under visible light irradiation. Similarly, for a co-existed phenol and Cr(VI) model system, Bi2MoO6/Bi2MoO6-x-catalyzed the photodegradation of phenol and the reduction of Cr(VI) simultaneously occur, and Bi2MoO6/Bi2MoO6-x homojunction also displays a superior photocatalytic activity, that is 4 and 8 times higher than pure Bi2MoO6, respectively. The remarkably boosted photocatalytic activity could be attributed primarily to the highly efficient separation of photogenerated electrons/holes due to the homojunction and the synergistic effect between phenol oxidation and Cr(VI) reduction. Thus, the present insight provides an effective strategy for designing and preparing highly active photocatalysts with the incorporation of oxygen vacancies modulation and applying for environmental remediation.

Photocatalytic performance and mechanism insights of a S-scheme g-C3N4/Bi2MoO6 heterostructure in phenol degradation and hydrogen evolution reactions under visible light.

Photocatalysis with potentially low cost and sustainable utilization is a typically environmentally benign method for the degradation of organic pollutants, but the rational design and fabrication of photocatalysts with high catalytic performance is still an enormous challenge. The efficient segregation of photogenerated electron-hole pairs in photocatalysts is a key and essential factor to decide photocatalytic activity. Herein, a novel Step-scheme (S-scheme) heterojunction photocatalyst, a g-C3N4/Bi2MoO6 (g-CN/BMO) composite, was successfully fabricated using g-C3N4 nanosheet-wrapped Bi2MoO6 microspheres. By adjusting the amount of g-C3N4 in BMO, a series of g-CN/BMO composites was prepared while optimizing posttreatment temperature. The resulting g-CN/BMO indicated well the photocatalytic performance for the degradation of phenol and hydrogen evolution reactions, especially, 100 g of g-CN was integrated into 100 g of the pre-calcined BMO at 200 °C to produce 100% g-CN/BMO-200, showing the highest photocatalytic performance compared to single composite BMO, BMO-200, g-CN, and g-CN/BMO-200 with other mass ratios. Combining the results from the density functional theory calculations and the results of X-ray photoelectron spectroscopy, for S-scheme heterojunction-structured g-CN/BMO-200, the internal electric field-, band edge bending- and coulomb interaction-driven efficient segregation of photogenerated electrons and holes at the interface is elucidated to explain the photocatalytic mechanism, and the resulting holes on the VB of BMO and electrons on the CB of g-CN are responsible for the improvement of the photocatalytic performance. This study revealed that for the S-scheme g-CN/BMO composite the internal electric field, band edge bending and coulomb interaction at the interface between g-CN and BMO can not only promote the effective segregation of electrons and holes, but also retain stronger redox ability. Such an investigation provides a facile and simple strategy to fabricate novel S-scheme heterojunction-structured photocatalysts for solar energy conversion.

Single yttrium sites on carbon-coated TiO2 for efficient electrocatalytic N2 reduction.

We report single yttrium sites anchored on carbon-coated TiO2 for efficient and stable electrocatalytic N2 fixation, delivering an NH3 faradaic efficiency exceeding 11.0% and an NH3 yield rate as high as 6.3 µgNH3 h-1 mgcat.-1 at low overpotentials, thus surpassing many reported metal electrocatalysts.

Efficient Degradation of Phenol and 4-Nitrophenol by Surface Oxygen Vacancies and Plasmonic Silver Co-Modified Bi2 MoO6 Photocatalysts.

In this work, the surface plasmon resonance effect of metallic Ag, surface oxygen vacancies (SOVs), and Bi2 MoO6 (BMO) material were rationally combined to construct new oxygen-vacancy-rich Ag/Bi2 MoO6 (A/BMO-SOVs) photocatalysts. Their synergistic effect on the photocatalytic degradation of phenol and 4-nitrophenol under visible-light irradiation (λ≥420 nm) was also investigated. TEM, EPR, and Raman spectra demonstrate the co-existence of metallic Ag nanoparticles, surface oxygen vacancies, and Bi2 MoO6 due to a controlled calcination process. The experimental results disclose that the 2 %A/BMO-SOVs-375 sample exhibited the highest photocatalytic activity for the degradation of both phenol and 4-nitrophenol under visible-light irradiation, achieving nearly 100 and 80 % removal efficiency, respectively, and demonstrated the apparent reaction rate constants (kapp ) 183 and 26.5 times, respectively, higher than that of pure Bi2 MoO6 . The remarkable photodegradation performance of A/BMO-SOVs for organic substances is attributed to the synergistic effect between the surface oxygen vacancies, metallic Ag nanoparticles, and Bi2 MoO6 , which not only improves the visible-light response ability, but also facilitates charge separation. Thus, this work provides an effective strategy for the design and fabrication of highly efficient photocatalysts through integrating surface oxygen vacancies and the surface plasmon resonance effect of nanoparticles, which has the potential for both water treatment and air purification.

Porous BiOBr/Bi2MoO6 Heterostructures for Highly Selective Adsorption of Methylene Blue.

Porous BiOBr/Bi2MoO6 (Br/Mo) heterostructures were designed and successfully fabricated, in which BiOBr nanoparticles were deposited on the surface of the secondary nanoplate of three-dimensional porous Bi2MoO6 architectures through a deposition-precipitation process. The as-prepared Br/Mo heterostructures were used as an adsorbent to remove methylene blue (MB) from aqueous solution. The batch adsorption results indicated that 50.0 wt % Br/Mo heterostructures show an enhanced adsorption capacity compared with pure Bi2MoO6 and BiOBr. The effects of initial solution, initial concentration, and contact time were systematically investigated. The optimum adsorbent amount and the pH value were determined to be 0.8 g L-1 and 2, respectively. Meanwhile, the experiments also revealed that porous Br/Mo heterostructures possess higher preferential adsorptivity for MB than that for methyl orange (MO-) and rhodamine B (RhB+). The dynamic experimental result indicated that the adsorption process conforms to the pseudo-second-order kinetic model. Weber's intraparticle diffusion model indicated that two steps took place during the adsorption process. Thermodynamic analysis results showed that the adsorption is a physisorption process, which conforms to the Langmuir isotherm model. Additionally, the possible adsorption mechanism was also investigated. The present study implied that Br/Mo heterostructures are promising candidates as adsorbents for MB removal. Therefore, fabrication of semiconductor-based heterostructures could be a strategy to design new efficient adsorbents for the removal of environmental pollutants.