Search

Construction of heterojunctions with matching energy band structures between two semiconductors displays great potential in promoting the separation and transfer of photogenerated charge carriers and is one of the effective strategies for obtaining high active photocatalysts. In this study, a type‐II heterojunction photocatalyst was designed and prepared using Bi2Fe4O9 (BFO) nanoparticles and hydrothermal‐treated red phosphorus (HRP). The photocatalytic performance test exhibited that the 3%BFO/HRP composite photocatalyst with 3% mass fraction of BFO rapidly and efficiently photoreduced Cr(VI), and the reduction was completed within 25 min, with a rate constant of 0.15 min−1, which was 15 times higher than that of pure HRP. Further mechanistic investigation revealed that the photocatalytic activity was enhanced due to the tight heterojunction between BFO and HRP, thereby effectively promoting carrier transfer, destroying the carrier recombination, and reducing the charge‐transfer resistance of composite catalyst. Mott–Schottky diagrams and UV‐vis diffuse reflectance spectroscopy data indicated the theoretical feasibility of establishing a close contact between BFO and HRP. X‐ray photoelectron spectroscopy provided evidence for the way in which interfacial charges were transferred. This work provides a new possibility to construct heterojunction photocatalysts for the rapid and efficient reduction of Cr(VI). [ABSTRACT FROM AUTHOR]

The release of a large number of antibiotics to the environment has created a shade of sorrow in the scientific community. Herein, two-dimensional (2D)–2D NiO/g-C3N4 photocatalysts were synthesized and applied for the photodegradation of tetracycline hydrochloride antibiotic. This 2D–2D heterojunction catalyst showed effective photoactivity due to the large contact area promoting the interfacial charge transfer rate. The improved photoactivities were attributed to the formation of complete face-to-face heterojunctional channels between two nanosheets of NiO and g-C3N4, which play a major contribution in the transfer of excited charges in the nanocomposite. Besides, the formation of Z-type heterojunction protects the high redox ability of two semiconductors. The photocatalytic activities were high at neutral pH values and decreased when pH values were changed. The photocatalytic activities were also checked in the presence of certain anions such as sulfate, chloride, carbonate), nitrate, and phosphate. Finally, a possible schematic mechanism was planned for charge separation in the nanocomposite. 2D-2D NiO/g-C3N4 photocatalysts demonstrate high photocatalytic activity for degradation of tetracycline hydrochloride antibiotic due to the large contact area and Z-scheme heterojunction promoting the interfacial charge transfer rate. [ABSTRACT FROM AUTHOR]

Under assistance of ionic liquid, the Cu 2 O crystal was successfully synthesized by a simple solution-phase method with several morphologies, including octahedrals, truncated octahedrals, facet-etched octahedrals, particle-coated octahedrals and aggregated spheres. The morphology of Cu 2 O crystals can easily be modified by tuning the adding amounts of ionic liquid 1-ethyl-3-methylimidazolium bromide. A possible growth mechanism for the crystal products can be suggested based on the DFT+ D calculation and experiments. Under visible-light irradiation (λ > 420 nm), the obtained Cu 2 O samples show an outstanding performance during photodegrading methylene blue (MB) dye. The higher photocatalytic activity for MB photodegradation by the Cu 2 O facet-etched octahedrals comparing to octahedrals can be attributed to the formation of surface heterojunction between (1 0 0) and (1 1 1) facets. Therefore, the ionic liquid-assisted solution-phase syntheses would be potentially useful in the fields of catalyst production for photodegrading hazardous pollutants. [ABSTRACT FROM AUTHOR]

• CuInS 2 /ZnS heterojunction photocatalysts are successfully prepared. • CuInS 2 /ZnS shows high photocatalytic performance. • High charge separation efficiency is due to the formation of S-scheme heterojunction. In last few years, the researchers from different communities are focusing the wastewater treatment of medical and aquaculture industry. More importantly, the antibiotic released from the hospitals and aquaculture badly effecting water bodies. In this work, a series of CuInS 2 /ZnS (CIS/ZnS) heterojunction nanomaterials are prepared through solvothermal method and analyzed using different techniques. The photocatalytic behavior of CIS/ZnS heterojunctions in the degradation of tetracycline hydrochloride (TCH) is investigated under visible light irradiation. The results show that up to 86% of TCH degrades in 3 h with the optimized CIS/ZnS(1:2) sample. The enhanced photocatalytic activity is attributed to the formation of S-scheme heterojunctions, which promotes charge separation and transportation in CIS/ZnS composite materials. The photocatalytic mechanism is elucidated based on the electron paramagnetic resonance technique, optical properties and charge/radical trapping experiments. The visible-light absorption ability is enhanced, and superoxide radical (•O 2 −) is confirmed to be one of the main active species according to active substance capturing experiments. The high stability of CIS/ZnS composite provides a new way to design effective photocatalysts for the eradication of hazardous materials from environment. S-scheme CuInS 2 /ZnS Heterojunctions are prepared via solvothermal approach and its photocatalytic activities are checked for tetracycline hydrochloride degradation. [Display omitted] [ABSTRACT FROM AUTHOR]

CeO 2 /hydrothermally treated red phosphorus (HRP) heterojunction composite was formed to address the easy recombination of carriers. The results of the composition proportion optimization revealed that the 5%CeO 2 /HRP composite (weight proportion of CeO 2 about 5wt%) showed the best photocatalytic degradation performance for Rhodamine B (RhB). The rate constant value of 5%CeO 2 /HRP was 0.071 min−1, which was 2.0 and 35.5 times more than that of pure HRP and CeO 2. In addition, the introduction of the heavy metal Cr(VI) to form a mixed heavy metal-organic pollutant solution significantly improved the removal of RhB due to the simultaneous removal of the two target pollutants could improve the utilization efficiency of photogenerated carriers. Mechanistic investigations proved that the heterojunction could be decreased the recombination ratio of photogenerated electron-hole pairs in single semiconductors, thereby enhancing its photocatalytic activity. This research not only offered a novel method for designing heterojunction photocatalytic materials, but also provided a fresh perspective on the treatment of mixed pollutants. • Oxygen vacancies in CeO 2 act as O 2 adsorption and reduction reaction sites. • 5%CeO 2 /HRP composite was designed to improve carrier separation and transport efficiency. • The heavy metals and organic pollutants could be removed simultaneously in the presence of the 5%CeO 2 /HRP composite. [ABSTRACT FROM AUTHOR]

Keeping in view of the hazardous application of tetracycline hydrochloride antibiotic, an efficient CoFe 2 O 4 /NiFe 2 O 4 heterojunction photocatalyst has been prepared hydrothermally by combining CoFe 2 O 4 and NiFe 2 O 4 nanoplates. The CoFe 2 O 4 /NiFe 2 O 4 composite with the improved photocatalytic activity can be employed for removal of tetracycline hydrochloride antibiotic, comparing to the bare CoFe 2 O 4 and NiFe 2 O 4. The optimized sample 5%-CoFe 2 O 4 /NiFe 2 O 4 shows the high photocatalytic degrading tetracycline with 76.1% removal efficiency in 60 min. These improved photocatalytic activities are attributed to the extended visible light absorption and enhanced charge separation following S-scheme route as confirmed from photoluminescence and electrochemical studies. From the charge trapping experiments, it is confirmed that superoxide radical and holes in the valence band of NiFe 2 O 4 with high thermodynamic energies are responsible for the photodegradation of the target pollutant. This work provides sufficient attention towards the preparation of low cost materials for the removal of highly hazardous pollutants being present in water. [ABSTRACT FROM AUTHOR]

[Display omitted] Red phosphorus (RP) has a suitable energy band structure and excellent photocatalytic properties. However, there are some problems, such as low quantum efficiency and serious photogenerated electron-hole recombination. The S-scheme heterostructure shows great potential in facilitating the separation and transfer of photogenerated carriers and obtaining strong photo-redox ability. Herein, hydrothermally treated red phosphorus (HRP) was combined with Bi 2 O 2 CO 3 to construct Bi 2 O 2 CO 3 /HRP S-scheme heterojunction composite. The Bi 2 O 2 CO 3 content was optimized, and the 5 %Bi 2 O 2 CO 3 /HRP composite obtained at 5 %Bi 2 O 2 CO 3 mass fraction exhibited the strongest photoreduction ability. The Cr(VI) photoreduction and photolytic hydrogen production rates were as high as 0.22 min−1 and 157.2 μmol •h−1, which were 7.3 and 3.0 times higher than those of HRP, respectively. The promoted photocatalytic activity could be attributed to the formation of S-scheme heterojunctions, which accelerated the separation and transfer of useful photogenerated electron-hole pairs, while enhancing the recombination of relatively useless photogenerated electron-hole pairs, thereby resulting in the highest photocurrent density (17.3 μA/cm2) of the 5 %Bi 2 O 2 CO 3 /HRP composite, which was 1.6 and 4.3 times higher than pure Bi 2 O 2 CO 3 (10.5 μA/cm2) and pure HRP (4.0 μA/cm2), respectively. This work would provide an advanced approach to enhance the photocatalytic activity of RP. [ABSTRACT FROM AUTHOR]

The construction of wide bandgap semiconductors with heterojunctions is an effective strategy to improve the photocatalytic activity of narrow-bandgap semiconductors, such as red phosphorus (RP). The novel step-scheme (S-scheme) heterojunction can separate photocarriers effectively while retaining the high reduction-oxidation capacity of the catalyst. Herein, a SnO 2 /hydrothermally treated RP (SnO 2 /HRP) S-scheme heterojunction was constructed and was found to display superior performance in the photocatalytic degradation of pollutants and the disinfection of bacteria. The 5%SnO 2 /HRP (mass ration of SnO 2 with 5 wt%) composite had the strongest photocatalytic activity. It could degrade 97.5% of Rhodamine B (RhB) after 12 min of light exposure. The photodegradation rate constant of this composite reached 2.96 × 10−1 min−1, which was 4.4 and 59.2 times higher than that of pure HRP and SnO 2 , respectively. Furthermore, this S-scheme heterojunction composite exhibited a higher efficient photocatalytic antibacterial rate (99.4%) for Escherichia coli (E. coli) under visible-light irradiation, than pure HRP (66.4%) and SnO 2 (72.9%). Further mechanistic investigations illustrated that the intimate contact between HRP and SnO 2 in the S-scheme system heterojunction could effectively boost carrier transfer and improve the photocatalytic activity of the semiconductor. This investigation provided an efficient recyclable S-scheme heterojunction composite for the photocatalytic degradation of pollutants and bacteria. [Display omitted] • SnO 2 /HRP S-scheme heterojunction accelerated transfer of photogenerated carriers. • Antibacterial rate of composite against E. coli was 99.4% after 30 min. • Photodegradation rate of composite was higher than that of HRP and SnO 2. • Much more hydroxyl radicals were generated in 5%SnO 2 /HRP composite. [ABSTRACT FROM AUTHOR]

• One facile way was adopted to prepare Bi 2 O 3 /HRP heterojunction composite. • The heterogeneous interface leads to enhanced separation and migration of charge carriers. • Photoreduction rate constant of 3%Bi 2 O 3 /HRP was 14.9 times that of HRP. • Photocatalytic mechanism in 3%Bi 2 O 3 /HRP system was studied in detail. In order to solve the problems of easy recombination of carriers and low efficiency of photocatalysis in red phosphorus photocatalyst, Bi 2 O 3 /HRP heterostructure composite photocatalyst was prepared by hydrothermal method. Cr(VI) was selected as the model contaminant to investigate the photoreduction activity of the photocatalysts. The experimental results revealed that the composite photocatalyst obtained at 3% Bi 2 O 3 mass fraction (3%Bi 2 O 3 /HRP) exhibited the strongest photoreduction ability, and its rate constant was 14.9 and 50 times that of pure HRP and Bi 2 O 3. The photoelectric conversion efficiency of the photocatalyst improved, which was illuminated by the high current density (16.7 and 42 times higher than that of HRP and Bi 2 O 3) and the heterogeneous interface that facilitated charge transfer and separation. On the basis of the matched band structure of Bi 2 O 3 and HRP, Bi 2 O 3 with wide band gap (E g) is introduced into HRP with narrow E g to form a heterojunction structure, which provides an effective strategy to promote space charge separation and transfer. [ABSTRACT FROM AUTHOR]