Organic–inorganic hybrid photocatalyst g-C 3 N 4 /Ag 2 CO 3 with highly efficient visible-light-active photocatalytic activity

Clay-based 1D-2D halloysite&g-C3N4 nanostructured meat floss for photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) has drawn extensive attention with some features including visible-light response as non-metallic semiconductor, low cost in raw material and green pollution-free for environment, but suffers from some issues such as fast charge carriers' recombination, easy aggregation, etc. In this work, the 1D-2D HNTs&g-C3N4-X binary materials similar to meat floss pattern in a series of halloysite loading amounts are designed via a facile electrostatic self-assembly strategy with debris g-C3N4 after cell pulverizing treatment and HNTs that outwardly modified by cetyltrimethylammonium bromide (CTAB) as the building blocks. The halloysite-mediated satellite-core material displays a photocatalytic of H2 evolution performance with the highest evolution rate of 137.0 μmol g-1 h-1 in visible light condition with no co-catalysts, and is ∼3.4 times that of bulk g-C3N4, mainly benefiting from the reduced nanometer size of debris g-C3N4 and enhanced interface dispersion ability by HNTs, resulting in ameliorative separation efficiency of photogenerated charge carriers. This research conclusively provides the new perspective towards the performance enhancement of water splitting of g-C3N4 in raw clay mineral modification mode and broadens the applications of mineral-based composite in the renewable energy utilization field.

Synthesis, characterization and properties of sulfate-modified silver carbonate with enhanced visible light photocatalytic performance

Sulfate-modified Ag₂CO₃ was successfully synthesized via a simple precipitation method. Its visible light photocatalytic performance against the removal of Orange G was found to be significantly enhanced in comparison with the one of pure Ag₂CO₃. While SO₄^2--Ag₂CO₃ ensured a removal efficiency of 100% of OG within 30 min, the unmodified Ag₂CO₃ exhibited a degradation threshold at hardly 60%. Likewise, the degradation rate constant in the presence of SO₄^2--Ag₂CO₃ photocatalyst was assessed to be twice that determined upon the involvement of pristine Ag₂CO₃. Furthermore, Total Organic Carbon (TOC) measurements evidenced the occurrence of a quasi-total mineralization of the dye pollutant upon the use of SO₄^2--Ag₂CO₃ photocatalyst. Scavenger experiments highlighted the dominant role of photo-induced h⁺ along with ˙O₃^- ozonide radicals in the OG photocatalytic oxidation mechanism. Reuse cycles revealed that the modification by SO₄^2- is a promising route to improve the stability of silver carbonate against photocorrosion. All these improvements could be ascribed to electronic transfer from the upper SO₄^2- HOMO to the lower Ag₂CO₃ conduction band.

A pectin/chitosan/zinc oxide nanocomposite for adsorption/photocatalytic remediation of carbamazepine in water samples

The present study investigates a synergistic adsorption/photodegradation technique catalyzed by a pectin/chitosan/zinc oxide (Pec/CS/ZnO) nanocomposite for the removal of carbamazepine (CBZ) in aqueous solutions under direct sunlight. The Pec/CS/ZnO nanocomposite was prepared by an inotropic gelation method and was characterized using different techniques. The adsorption/photocatalytic activity of the Pec/CS/ZnO nanocomposite for the remediation of CBZ was optimized using Box-Behnken design under response surface methodology. The examined parameters included the amount of Pec/CS/ZnO nanocomposite (0.25-0.75 g L-1), pH (4-10), and run time for adsorption/photo-irradiation (1-5 hours). The efficiency of CBZ degradation was calculated in terms of changes in CBZ concentration using a validated chromatographic assay. The optimum conditions for the remediation of CBZ were 0.5 g L-1 Pec/CS/ZnO nanocomposite, pH 4, and 3 hour run time. Under such conditions, the degradation efficiency of 10 mg L-1 CBZ was found to be 69.5% with a rate constant (k) of 0.00737 min-1 and half-life time of 94 min. The efficiency of the Pec/CS/ZnO nanocomposite for CBZ remediation was found to be stable and consistent after three cycles of reuse. The presence of other pharmaceutical contaminants such as acetaminophen in wastewater samples was also investigated. The efficiency of CBZ degradation was not significantly affected by the addition of acetaminophen in a 0-15 mg L-1 concentration range which confirmed the selectivity and efficiency of the proposed method for CBZ degradation and removal.

Dual plasmons-promoted electron-hole separation for direct Z-scheme Bi3O4Cl/AgCl heterojunction ultrathin nanosheets and enhanced photocatalytic-photothermal performance

The dual plasmons (Bi, Ag)-based direct Z-scheme Bi₃O₄Cl/AgCl heterojunction ultrathin nanosheets are successfully synthesized by hydrothermal combined with solid-state reduction strategy. The plasmons Ag and Bi are formed during solid-state reduction process, which are firmly anchored on surface of Bi₃O₄Cl and AgCl, respectively, and favors the charge transfer obviously. Experiments results confirm the formation of heterojunction ultrathin nanosheets with the main size of 200∼300 nm and the thickness of <10 nm. The obtained dual plasmons-based direct Z-scheme Bi₃O₄Cl/AgCl heterojunction ultrathin nanosheets with the band gap of ∼1.66 eV exhibit excellent photothermal performance. 98.3% of Cr (VI) can be photocatalytic reduced and TOC removal rate of ceftriatone sodium reached 98.9% within 210 min, respectively. Due to the surface plasma resonance, the catalyst temperature increases obviously, indicating the enhanced photothermal performance, which is favorable for promoting the photocatalytic performance. Moreover, the cyclic stability experiment also proves the high stability and has advantages in practical applications. The excellent property can be ascribed to the direct Z-scheme accelerating charge transfer and prolonging the lifetimes, the dual plasmons enhancing photothermal performance and the spatial separation of photogenerated charge carriers.

Highly efficient visible-light photoactivity of Z-scheme MoS2/Ag2CO3 photocatalysts for organic pollutants degradation and bacterial inactivation

Here, a novel Z-scheme MoS₂/Ag₂CO₃ heterojunction photocatalyst was assembled from two-dimensional MoS₂ nanosheets and Ag₂CO₃ nanoparticles through facile hydrothermal and in-situ precipitation method. The MoS₂/Ag₂CO₃ heterojunction exhibited much enhanced visible-light photocatalytic performance in probe experiment for organic pollutants degradation and Escherichia coli (E. coli) inactivation compared to pristine Ag₂CO₃ and MoS₂. The degradation rates of Lanasol Red 5B, rhodamine B, ciprofloxacin, and metronidazole reached 95%, 90%, 80%, and 72%, respectively. On the other hand, E. coli was completely inactivated in 80 min in the presence of 5%-MoS₂/Ag₂CO₃. The improved photocatalytic performance was ascribed to the enhanced photogenerated charge separation efficiency and increased lifetime of the charge carriers, proved by photoluminescence spectra, time-resolved fluorescence emission decay spectra, and electrochemical measures. In addition, the active species trapping and ESR experiments all indicated that holes (h⁺) exhibited a significant contribution and superoxide radicals (O₂^-) acted as assistants. Based on experiment results, the photocatalytic enhancement mechanism for organic pollutants degradation and E. coli inactivation was discussed. The effect of representative environmental factors on the degradation of Lanasol Red 5B was investigated. The experiment results indicated that the degradation efficiency was partially influenced in the presence of inorganic salt. Furthermore, the appearance of a small amount of Ag nanoparticles not only enhanced the charge transfer, but also improved the stability of photocatalyst. Overall, MoS₂/Ag₂CO₃ heterojunction has a great application potential for future water purification.

Synthesis of LaFeO3/Ag2CO3 Nanocomposites for Photocatalytic Degradation of Rhodamine B and p-Chlorophenol under Natural Sunlight

Novel LaFeO3/Ag2CO3 nanocomposites are synthesized by co-precipitation method for photocatalytic degradation of Rhodamine B (RhB) and p-chlorophenol under visible light irradiation. Heterostructures between LaFeO3 and Ag2CO3 semiconductors are formed during the synthesis of these nanocomposites. Among the nanocomposites prepared with different ratios of LaFeO3 and Ag2CO3, 1% LaFeO3/Ag2CO3 shows the highest photocatalytic activity for the degradation of RhB. Maximum electron-hole pair decoupling efficiency is observed in 1% LaFeO3/Ag2CO3, which causes the greater activity of the heterostructure. Degradation efficiency of 99.5% for RhB and 59% for p-chlorophenol has been obtained under natural sunlight within 45 min. Interestingly, the stability of Ag2CO3 is improved dramatically after making nanocomposite, and no decomposition of the catalyst was observed even after several photocatalytic cycles. Reactive oxygen species scavenging experiments with p-benzoquinone, isopropyl alcohol, and ammonium oxalate suggest that a major degradation process is caused by holes. Degradation of RhB into small organic moieties is detected using LC-MS technique. Further, the efficient mineralization of the degradation products occurs during the catalytic process.

Influence of g-C3N4 Precursors in g-C3N4/NiTiO3 Composites on Photocatalytic Behavior and the Interconnection between g-C3N4 and NiTiO3

In this study, composite photocatalysts were produced from NiTiO₃ and N₂-rich precursors (dicyandiamide, melamine, urea, and thiourea) under N₂ flow conditions. The goal of the study was to investigate the interaction between NiTiO₃ and the synthesized g-C₃N₄. The properties of the g-C₃N₄/NiTiO₃ (CNT) composites were different depending on the starting materials. Dicyandiamide and thiourea created strong connections with NiTiO₃ and resulted in the generation of Ti-N and Ti-O-S bonds. Urea and melamine, however, had difficulty forming g-C₃N₄ structures or interconnections with NiTiO₃. The Ti-N and Ti-O-S bridges in the composite photocatalysts led to increased photocatalytic activity as well as inhibition of the recombination rate. Additionally, the band diagrams of g-C₃N₄ prepared from dicyandiamide and thiourea exhibited positions suitable for the Z-scheme charge-transfer model with NiTiO₃, implying that the composite photocatalysts were applicable for photocatalytic degradation of organic contaminants under the visible-light irradiation. Higher reaction rate constants for the composites prepared with dicyandiamide and thiourea confirmed the significant role of the Ti-N/Ti-O-S bridge between g-C₃N₄ and NiTiO₃.

Sono-precipitation of Ag2CrO4-C composite enhanced by carbon-based materials (AC, GO, CNT and C3N4) and its activity in photocatalytic degradation of acid orange 7 in water

Enhancing the photocatalytic activity of Ag₂CrO₄ with coupled carbon-based materials like activated carbon, graphene oxide, carbon nanotubes and carbon nitride has been investigated in removal of Acid Orange 7 from wastewater. Sono precipitated Ag₂CrO₄-C composite based photocatalysts were characterized by XRD, BET, FESEM, FTIR and UV-vis DRS and the photocatalytic activity of theses samples was evaluated in terms of degradation amount of acid orange 7 under visible light irradiations. BET analysis showed that with addition of carbon based materials, the specific surface area of the Ag₂CrO₄-C composite increased. XRD analysis indicated that the crystallinity of Ag₂CrO₄ peaks decreased after addition of all studied carbon-based materials and C₃N₄ has lowered the crystallinity of Ag₂CrO₄ less than others. Higher crystallinity has the positive effect of higher photocatalytic activity because among above mentioned composites, Ag₂CrO₄-C₃N₄ photocatalyst exhibited higher photocatalytic activity and stability under visible light irradiations. DRS analysis confirmed good match of electronic structures of Ag₂CrO₄ and C₃N₄. On the other hand Ag₂CrO₄ and C₃N₄ formed heterojunction which separates photo-generated electron-hole pairs effectively. Also evaluation of photocatalytic reaction in various operating parameters showed Ag₂CrO₄-C₃N₄ had the highest photocatalytic activity in neutral pH and 1g/L of catalyst loading.

Photocatalytic activities and photoinduced fusion of gold-modified titania nanoparticle

Gold nanoparticles measuring 3–30 nm deposited on semiconductors result in an effective photocatalyst against several pollutants. Its photocatalytic activities are significant under both UV and solar irradiation. In a photocatalytic system, the oxidation of pollutants takes place on the gold surface as the electron donor, while the electron is consumed by the reduction of oxygen as the electron acceptor on the semiconductor’s surface. This promotes not only increased photocatalytic activities but also the green transformation of pollutant compounds to harmless compounds. The photosensitivity of semiconductors can be modified by tuning the size, shape, and contact of gold nanoparticles. This review highlights the function of gold nanoparticles in overcoming the limitation of transition metal oxide materials in photocatalytic applications.

g-C3N4/Bi4O5I2 2D–2D heterojunctional nanosheets with enhanced visible-light photocatalytic activity

The 2D–2D heterojunctional g-C₃N₄/Bi₄O₅I₂ nanosheets were successfully constructed based on band gap engineering design. It exhibits high visible-light-driven photocatalytic activity for degradation of RhB and NO removal.

Fabrication and characterization of Ag2CO3/SnS2 composites with enhanced visible-light photocatalytic activity for the degradation of organic pollutants

The efficient charge transfer at the interfaces of the Ag₂CO₃/SnS₂ composite due to the inner established electric field (E), which effectively facilitated interfacial charge transfer and improved photogenerated electron–hole pairs separation.