The novel ternary Fe3N/Fe2O3/C3N4 photocatalyst was prepared by thermal pyrolysis of potassium ferricyanide in melamine. The structural, morphological and physico-chemical properties of the ...photocatalyst were characterized by a multi-technique approach. Photocatalytic experiments supported that 0.04 g of the photocatalyst was able to totally remove 5 ppm of rhodamine B (RhB) solution under acidic condition with the rate constant of 0.1 min−1 in less than 30 min. According to spin-trapping ESR analysis, •OH radicals play a key role in the RhB photodegradation implying Z-scheme mechanism is applicable to our system. Moreover, the evolution rate of CO and CH4 over the photocatalyst was 8.03 and 1.6 μmol g−1 h−1, respectively, which was much higher than the reference photocatalysts under the same conditions. The enhanced photocatalytic performance of this system is attributed to the unique ternary heterojunction between the interfaces of g-C3N4, Fe3N and Fe2O3, which effectively suppressed the charge carriers recombination.
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•A novel ternary Fe3N/Fe2O3/C3N4 photocatalyst was prepared from cheap raw materials.•The interfacial Fe3N regions act as electron mediator and bandgap modifier.•The mechanism of RhB photodegradation was well discussed based on EPR experiments.•The ternary Fe3N/Fe2O3/C3N4 photocatalyst showed efficient photocatalytic CH4 evolution performance.
Abatement of mercury emissions in air and waters has become a global challenge due to the toxicity of mercury species for life, yet actual remediation techniques are limited. In particular, ...adsorption of mercury ions onto solids is widely used but most adsorption techniques are not specific, and in turn, removal efficiency is lower. Adsorbents developed so far include activated carbon, clay, bentonite, cellulose and chitosan. Chitosan derivatives have recently attracted research attention for water purification because their molecular frames contain a large amount of −NH2 and −OH groups that can chelate with metal ions specifically. This manuscript reviews recent advances in chitosan‐based adsorbents designed to remove mercury ions from wastewater. Focus is placed on their design, synthesis, characterization, adsorption properties, adsorption mechanisms and applications.
Chitosan is an excellent bio‐adsorbent for metal ions removal because of the large number of −NH2 groups. A series of chitosan derivatives have been obtained by crosslinking with glutaraldehyde among others or by grafting new functional groups on the chitosan backbone with the aim of adsorbing Hg(II) ions. The new functional groups allow to change the pH range for Hg(II) ions adsorption, to change the adsorption sites in order to increase adsorption capacity and efficiency, and to enhance sorption selectivity.
Highlights
The latest advancements in Cu-based catalysts for photocatalytic and electrocatalytic CO
2
reduction into C
2+
products are reported.
The relationship between the Cu surfaces and their ...efficiency in photocatalytic and electrocatalytic CO
2
reduction is emphasized.
The opportunities and challenges associated with Cu-based materials in the CO
2
catalytic reduction applications are presented.
Carbon dioxide conversion into valuable products using photocatalysis and electrocatalysis is an effective approach to mitigate global environmental issues and the energy shortages. Among the materials utilized for catalytic reduction of CO
2
, Cu-based materials are highly advantageous owing to their widespread availability, cost-effectiveness, and environmental sustainability. Furthermore, Cu-based materials demonstrate interesting abilities in the adsorption and activation of carbon dioxide, allowing the formation of C
2+
compounds through C–C coupling process. Herein, the basic principles of photocatalytic CO
2
reduction reactions (PCO
2
RR) and electrocatalytic CO
2
reduction reaction (ECO
2
RR) and the pathways for the generation C
2+
products are introduced. This review categorizes Cu-based materials into different groups including Cu metal, Cu oxides, Cu alloys, and Cu SACs, Cu heterojunctions based on their catalytic applications. The relationship between the Cu surfaces and their efficiency in both PCO
2
RR and ECO
2
RR is emphasized. Through a review of recent studies on PCO
2
RR and ECO
2
RR using Cu-based catalysts, the focus is on understanding the underlying reasons for the enhanced selectivity toward C
2+
products. Finally, the opportunities and challenges associated with Cu-based materials in the CO
2
catalytic reduction applications are presented, along with research directions that can guide for the design of highly active and selective Cu-based materials for CO
2
reduction processes in the future.
Graphitic carbon nitride based heterojunction photocatalysts have gained increasing attention in producing the clean energy source of hydrogen. Coupling carbon nitride (g-C3N4) with other ...semiconductor materials or metals as co-catalysts is considered as an effective strategy to overcome the drawbacks of g-C3N4 such as the quick recombination of photogenerated charges. In this review, the recent research advancements in the construction of g-C3N4-based heterojunctions as well as their different charge separation/transfer mechanisms will be systematically discussed, making special emphasis on the design and fabrication of type-II, Z-scheme, S-scheme and Schottky heterojunctions and their application towards H2 generation from water splitting. Finally, a summary and some crucial issues, which should be further resolved for developing advanced g-C3N4-based heterojunction photocatalysts, are presented.
Fe–Cu–ZSM-5 and Ce–Fe–Cu–ZSM-5 solids prepared using solid-state ion exchange method (SSIE) were tested in the NH
3
–SCR of NO reaction and were characterized using N
2
physisorption at 77 K, MAS
27
...Al magnetic resonance, X-ray diffraction, scanning electron microscopy, EPR spectroscopy and transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy in order to follow the effect of Ce addition on the textural and structural properties of Fe–Cu–MFI system as well as the detection of the changes in local environment and state of iron and copper species, and the degradation of the zeolite texture and structure after a severe aging treatment at 850 °C for 5 h. Fresh Ce-promoted sample showed better NO conversion up to 450 °C than unpromoted Fe–Cu–ZSM-5 catalyst. An activity loss was observed on aged catalysts, but remaining less pronounced for the catalyst containing Ce. The changes in catalyst structure and texture did not occur during aging, while a probable migration of metal active species and change in their coordination has occurred.
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To solve the aggregation problem of TiO2 nanomaterials and improve the catalytic efficiency, F-doped TiO2/exfoliated bentonite (TF/EB) composite was prepared by dispersing F-doped ...TiO2 (TF) nanoparticles on an exfoliated bentonite (EB) using a facile sol–gel method. The exfoliated bentonite was prepared by liquid-exfoliation method from the natural bentonite (B). The prepared samples were applied for toluene degradation in gas phase under UV and visible light irradiation. The as-prepared TF/EB composite exhibited higher toluene degradation efficiency than that of pure TiO2, F-doped TiO2 and TF/B composite. Results indicated that the calcination temperature and the initial F/Ti atom ratio of reaction precursors greatly affected the photocatalytic activity towards toluene degradation. The best photocatalytic performance was obtained by the sample calcinated at 400 °C with an initial F/Ti atom ratio of 5%. The improved photocatalytic performance is ascribed to a series of benefits introduced by F-doping and exfoliation process. The presence of F- ions increases the percentage of exposedreactive {001} facets on TiO2. Moreover, F- ions incorporated into the TiO2 lattice generate oxygen vacancies and Ti3+ defects, which influence the transfer and migration of the photoinduced charge carriers and induce a visible-light photocatalytic activity. Furthermore, the electrostatic interaction of negatively charged exfoliated bentonite surface leads to a more efficient separation of charge carriers.
Oxygen-doped ZnI2S4 nanosheets were synthesized by a one-pot solvothermal method and exhibited excellent photocatalytic activity for visible-light photocatalytic CO2 reduction to CO.
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...Engineering the electronic properties of semiconductor-based photocatalysts using elemental doping is an effective approach to improve their catalytic activity. Nevertheless, there still remain contradictions regarding the role of the dopants played in photocatalysis. Herein, ultrathin ZnIn2S4 (ZIS) nanosheets with oxygen doping were synthesized by a one-pot solvothermal method. XRD, XPS and Raman spectral measurements support the presence of lattice oxygen in the oxygen-doped ZIS (O–ZIS) sample. With optimum doping of oxygen, the ultrathin O–ZIS nanosheets show enhanced CO2-to-CO conversion activity with a CO-evolving rate of 1680 μmol h−1 g−1 under visible light irradiation, which is about 7 times higher than that of the pristine ZIS. First-principle calculations support that doping of oxygen in the lattice of ZnI2S4 nanosheets plays a key role in tuning its electronic properties.The remarkable photocatalytic performance of O–ZIS can be assigned to a synergistic consequence of a unique ultrathin-layered structure and an upward shift of the conduction band minimum (CBM) caused by the oxygen doping into ZIS and the quantum confinement effect (QCE) induced by the decreased particle size after doping as well as to the improved charge separation efficiency. The present work offers a simple elemental doping method to promote charge separation at atomic level and illustrates the roles playedby oxygen doping in photocatalysis, giving new insights into highly efficient artificial photosynthesis.
Photocatalysis is regarded as a promising technology for removal of nitrogen oxide (NO), however, the low photocatalytic efficiencies under visible light irradiation and the deactivation of the ...photocatalyst are as yet the significant issues that should be addressed. In this work, visible-light-driven Bi2Ti2O7/CaTiO3 heterojunction composites were synthesized by a facile in-situ hydrothermal method. The Bi2Ti2O7/CaTiO3 composites displayed superior visible light photocatalytic activity than pure CaTiO3 and pure Bi2Ti2O7 in the removal of NO at the 600 ppb level in air. Among all the composites, Bi2Ti2O7/CaTiO3 containing 20 wt% Bi2Ti2O7 exhibited the best photocatalytic activity, achieving a maximum removal efficiency of 59%. The improved photocatalytic performance is mainly attributed to the strong visible-light-absorbing ability, the presence of an appropriate density of oxygen vacancy defects and the formation of heterojunction between CaTiO3 and Bi2Ti2O7, resulting in an efficient charge separation at the interface as proven by photoluminescence (PL) and photo-induced current measurements. According to trapping experiments and spin-trapping ESR analysis, the •O2− and h+ are the principal reactive species involved in the photocatalytic NO removal. In addition, the as-obtained Bi2Ti2O7/CaTiO3 composite showed good chemical stability, which is beneficial for practical applications in air pollution removal.
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•Bi2Ti2O7/CaTiO3 composites were synthesized by a facile hydrothermal method.•The Bi2Ti2O7/CaTiO3 composites showed enhanced visible-light photocatalytic activity for NO removal.•The Charge transfer mechanism in Bi2Ti2O7/CaTiO3 composite was discussed in detail.•The NO removal pathway was proposed.
Over the past few decades, biological hazards and organic pollution have become major environmental concerns. Photocatalysis has been found to be effective in minimizing the negative impacts of these ...issues in air and water. Lozenge shape Ag/AgCl/ZnTiO3 photocatalysts were fabricated by a facile two-step synthesis method, including hydrothermal and coprecipitation. The physicochemical characteristics and morphological properties of the structures were comprehensively described taking advantage of a multi-technique approach. The prepared photocatalysts offered excellent nitrophenol mineralization (>90%) after 90 min of visible light irradiation. Based on the spin-trapping ESR technique, •O2̅– was recognized as the eminent reactive species during the photocatalytic process. Interestingly, the plasmonic Ag/AgCl/ZnTiO3 photocatalyst presented promising CO2 to CO/CH4 conversion with a production rate of 95.0/18.5 μmol.g−1.h−1 under visible light irradiation, which is about 1.6 times higher than that of ZnTiO3, implying the synergetic effects due to Ag/AgCl in the ternary construction. In addition to the investigation of antibacterial activity, the prepared photocatalysts were successfully applied to treat the hazardous biological waste bearing U87-MG cancer cells under visible light for the first time. Several as-related analytical techniques were served to demonstrate the activity and interaction pathways. This work may hone a new insight into designing highly efficacious ternary photocatalytic materials.
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•Fabrication of novel lozenge shape Ag/AgCl@ZnTiO3 photocatalysts.•Efficient photocatalytic removal of nitrophenols under visible light.•Productive conversion of CO2 to CO/CH4 over the photocatalysts.•Efficient treatment of the biological waste by the photocatalysts.•Mechanistic discussion of the photocatalytic pathways based on promising techniques.
Ammoxidation of ethylene to acetonitrile was studied on V/ZSM-5, Mo/ZSM-5 and V-Mo/ZSM-5 catalysts prepared by a solid-state ion exchange method. The physico-chemical properties were investigated by ...means of XRD, N
2
physisorption,
27
Al and
29
Si MAS NMR, UV-Vis DRS, XPS, pyridine-IR and FT-IR spectroscopies and H
2
-TPR/O
2
-TPO. Based on the characterization results, M-O
x
(M = V or Mo) species react with zeolite protons during the exchange process and generate new Lewis acid sites, which act as redox centers. The M-O
x
species are essentially, monomeric and dimeric/polymeric species or metal oxide crystallites (less than 4 nm) highly dispersed in the channel and/or on the external surface of zeolite. For the Mo/ZSM-5 sample, the formation of Al
2
(MoO
4
)
3
nano-crystallites was observed. UV-Vis DRS and TPR results showed that V and Mo species in all catalysts are mainly in the highest oxidation states. The V-Mo/ZSM-5 catalyst exhibited a more reversible behavior of the M-O
x
centers throughout the H
2
/O
2
redox cycles than those in V/ZSM-5 and Mo/ZSM-5 catalysts. The best catalytic performance was achieved over the bimetallic V-Mo/ZSM-5 catalyst. These results revealed that the partial substitution of molybdenum with vanadium has a positive effect on the activity and the selectivity to acetonitrile. This implies clearly that a synergetic effect between V and Mo species plays an important role in the ammoxidation reaction. This synergetic effect is related to the existence of electronic interaction at short range order between the V and Mo species, which may influence the catalyst redox properties.
Ammoxidation of ethylene to acetonitrile was studied on V/ZSM-5, Mo/ZSM-5 and V-Mo/ZSM-5 catalysts prepared by a solid-state ion exchange method.
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