In situ growing of Bi/Bi2O2CO3 on Bi2WO6 nanosheets for improved photocatalytic performance

Construction of Z-scheme Ag-AgBr/Bi2O2CO3/CNT heterojunctions with remarkable photocatalytic performance using carbon nanotubes as efficient electronic mediators

It is a useful strategy to use a solid electronic mediator with good conductivity to assist the separation of semiconductor photo-induced electron-hole pairs and the redox of semiconductor materials. In order to construct a photocatalyst for more efficient photocatalytic degradation of antibiotics, a simple hydrothermal and precipitation method was used to construct the Ag-AgBr/Bi₂O₂CO₃/CNT Z-scheme heterojunction by using carbon nanotubes (CNTs) as electronic mediators. Compared with the pristine AgBr, Bi₂O₂CO₃, Bi₂O₂CO₃/CNT, the 30%Ag-AgBr/Bi₂O₂CO₃/CNT photocatalyst has better photocatalytic activity under visible light irradiation, showing the best degradation ability to tetracycline (TC). Meanwhile, the photocatalytic properties of 30%Ag-AgBr/Bi₂O₂CO₃/CNT in different pH and inorganic ions were studied. Finally, the degradation pathway and catalytic mechanism of 30%Ag-AgBr/Bi₂O₂CO₃/CNT photocatalytic degradation of TC were also argued. The construction of the Z-scheme electron transport pathway, in which CNTs were used as electronic mediators, and the SPR effect of Ag and Bi metal, which enable the effective separation and transfer of photo-generated electron-hole pairs, are responsible for the significant improvement in photocatalytic performance. It opens up new possibilities for designing and developing high-efficiency photocatalysts with CNTs as the electronic mediator.

Degradation of tetracycline by FeNi-LDH/Ti3C2 photo-Fenton system in water: From performance to mechanism

Recently, photo-Fenton technology has been widely used to degrade tetracycline (TC) because of its great efficiency and wide application range. Herein, Fe-Ni layered double hydroxides (FeNi-LDH)/Ti₃C₂ photo-Fenton system was constructed in this study. The results showed the introduction of Ti₃C₂ solved some problems of FeNi-LDH such as poor conductivity, easy aggregation, and high recombination rate of photoelectron. Benefiting from these advantages, FeNi-LDH/Ti₃C₂ exhibited excellent TC removal rate of 94.7% while pure FeNi-LDH was only 54%. Besides, FeNi-LDH/Ti₃C₂ possessed strong pH tolerance (2-11) and the removal efficiency was still up to 82% after the four-cycle experiment. Furthermore, the quenching experiments revealed the reaction mechanism, where ∙OH and ·O₂^- were the primary active radicals for degrading TC. Last, the results of the simulated wastewater treatment and the inorganic ion interference tests showed that FeNi-LDH/Ti₃C₂ possessed practical application potential. In brief, this study shows that FeNi-LDH/Ti₃C₂ can offer a certain theoretical basis for the actual development of hydrotalcite in heterogeneous photo-Fenton systems.

Photocatalyst prepared by NiCo2O4/CNQDs modified carbon fabric heterojunctions enhanced visible-light-driven photocatalytic degradation of Methyl Orange

As this point, A novel photocatalyst was reported by us, cobalt nickel tetroxide (NiCo2O4)/g-C3N4 quantum dots (CNQDs) heterojunctions on carbon cloth (CC). NiCo2O4 nanosheets and NiCo2O4/CNQDs were grown on carbon...

Interfacial charge dynamics in type-II heterostructured sulfur doped-graphitic carbon nitride/bismuth tungstate as competent photoelectrocatalytic water splitting photoanode

Sluggish charge transfers at the electrode/electrolyte interface and fast recombination of electron-hole pairs limit the photoelectrocatalytic water-splitting ability of the bismuth tungstate (Bi₂WO₆). To address these issues, sulfur doped-graphitic carbon nitride/bismuth tungstate (S-g-C₃N₄/Bi₂WO₆) heterostructured hybrid material with different wt% of S-g-C₃N₄ were constructed via an ultrasonic approach. The formation of heterostructure offers well-separated electron-hole pairs, thereby improving the charge transfer process, and boosting water oxidation kinetics on the surface of modified electrodes. Electrochemical impedance analysis confirms the rapid charge transfer process and quick electrochemical reaction at the electrode/electrolyte interface, which quenches the charge recombination process. The S-g-C₃N₄/Bi₂WO₆ with 3 wt% of S-g-C₃N₄ photoanode delivers ~43, ~18 and ~2-folds higher applied bias photon-to-current efficiency than S-g-C₃N₄, Bi₂WO₆, and g-C₃N₄/Bi₂WO₆ (3 wt% of g-C₃N₄) photoanodes, respectively. From the combination of UV-Vis, XPS valance band, and Mott-Schottky analysis the plausible band edge positions of the Bi₂WO₆ and S-g-C₃N₄ were calculated. Based on the band structure, we have concluded that the S-g-C₃N₄/Bi₂WO₆ hybrid photoanode follows a type-II charge transfer mechanism to promote the photoelectrocatalytic water splitting ability.

Removal of elemental mercury by photocatalytic oxidation over La2O3/Bi2O3 composite

La₂O₃/Bi₂O₃ photocatalysts were prepared by impregnation of Bi₂O₃ with an aqueous solution of lanthanum precursor followed by calcination at different temperatures. The composite materials were used for the first time for the photocatalytic removal of Hg⁰ from a simulated flue gas under UV light irradiation. The results showed that the sample containing 6 wt.% La₂O₃ and calcined at 500°C has the highest dispersion of the active sites, which was promoted by the strong interaction with the support (i.e., the formation of Bi-O-La species). Since they are fully accessible on the surface, the material also exhibits excellent optical properties while the heterojunction formed in La₂O₃/Bi₂O₃ promotes the separation and migration of photoelectron-hole pairs and thus Hg⁰ oxidation efficiency is enhanced. The effects of the various factors (e.g., the reaction temperature and composition of the simulated flue gas (i.e., O₂, NO, H₂O, and SO₂)) on the efficiency of the Hg⁰ photocatalytic oxidation were investigated. The results demonstrated that O₂ and SO₂ enhanced the efficiency of the reaction while the reaction temperature, NO, and H₂O had an inhibitory effect.

Unique 1D/2D Bi2O2CO3 nanorod-Bi2WO6 nanosheet heterostructure: synthesis and photocatalytic performance

A novel 1D/2D Bi2O2CO3–Bi2WO6 heterostructure was synthesized by high temperature calcination. These 1D/2D Bi2O2CO3–Bi2WO6 heterostructures displayed an outstanding photocatalytic activity to degrade organic compounds.

Efficient combustion of chlorinated volatile organic compounds driven by natural sunlight

Catalytic combustion of chlorinated volatile organic compounds (CVOCs) driven by natural sunlight is the promising CVOCs elimination method, which has not been realized. In this work, we designed a new sunlight-driven catalytic system for CVOCs combustion based on a scalable CuMnCeO_x gel and a new photothermal conversion device. The CVOCs elimination rate of CuMnCeO_x gel was reached to 99% at 250 °C, 25 times higher than that of CuMnCeO_x in bulk form. Further, the new photothermal conversion device could heat the CuMnCeO_x gel to 300 °C under one standard solar irradiation and this joint showed a stable one standard sunlight-driven CVOCs combustion at the rate of 6.8 mmol g^-1 h^-1, which was more than 7.8 times higher than the state of the art of photocatalytic CVOCs decomposition. Moreover, the new sunlight-driven thermal catalytic system was able to stable full oxidize the CVOCs in the concentration from 0.1 to 1000 ppm. Therefore, the natural sunlight-driven thermal CVOCs combustion system with high activity and zero secondary pollution shows the potential for large-scale industrial applications.

Nanocarbon-Enhanced 2D Photoelectrodes: A New Paradigm in Photoelectrochemical Water Splitting

Solar-driven photoelectrochemical (PEC) water splitting systems are highly promising for converting solar energy into clean and sustainable chemical energy. In such PEC systems, an integrated photoelectrode incorporates a light harvester for absorbing solar energy, an interlayer for transporting photogenerated charge carriers, and a co-catalyst for triggering redox reactions. Thus, understanding the correlations between the intrinsic structural properties and functions of the photoelectrodes is crucial. Here we critically examine various 2D layered photoanodes/photocathodes, including graphitic carbon nitrides, transition metal dichalcogenides, layered double hydroxides, layered bismuth oxyhalide nanosheets, and MXenes, combined with advanced nanocarbons (carbon dots, carbon nanotubes, graphene, and graphdiyne) as co-catalysts to assemble integrated photoelectrodes for oxygen evolution/hydrogen evolution reactions. The fundamental principles of PEC water splitting and physicochemical properties of photoelectrodes and the associated catalytic reactions are analyzed. Elaborate strategies for the assembly of 2D photoelectrodes with nanocarbons to enhance the PEC performances are introduced. The mechanisms of interplay of 2D photoelectrodes and nanocarbon co-catalysts are further discussed. The challenges and opportunities in the field are identified to guide future research for maximizing the conversion efficiency of PEC water splitting.

Enhanced photocatalytic performance of metal silver and carbon dots co-doped BiOI photocatalysts and mechanism investigation

The photocatalytic technology provides a promising and effective strategy for the transformation and degradation of contaminants. Herein, we accurately fabricated a novel ternary photocatalyst, namely, metal silver (Ag) and carbon dots (CDots) co-doped BiOI nanocomposite (Ag/CDots/BiOI) via the reduction method with ionic liquids 1-butyl-3-methylimidazolium iodine ([Bmim]I) at room temperature. The morphologies and microstructures showed the Ag and CDots were uniformly loaded on the surface of BiOI, forming a ternary system. The characterization results implied that an intense interaction was formed between Ag and CDots on the BiOI, which could achieve the broad spectrum utilization of visible light and boosted the photocatalytic performances. The 0.9-Ag/2-CDots/BiOI (0.9 wt% of Ag, 2 wt% of CDots) presented the highest photocatalytic activity with ~ 100% in 4-Chlorophenol, 68.8% in mineralization, and 87.4% in dechlorination in 6 h under visible light illumination. The enhanced photocatalytic activity could be ascribed to the surface plasmon resonance effect of Ag, the up-converted photoluminescence (PL) properties of CDots, and the electron transfer properties of both Ag and CDots. Moreover, a possible photocatalytic reaction mechanism was discussed in detail by band structure analysis and radical scavenger quenching experiments. This study provides a promising approach for promoting the utilization efficiency for solar energy and sustainable environmental remediation.

Facet-, composition- and wavelength-dependent photocatalysis of Ag2MoO4

Faceted β-Ag₂MoO₄ microcrystals are prepared by controlled nucleation and growth in diethylene glycol (DEG) or dimethylsulfoxide (DMSO). Both serve as solvents for the liquid-phase synthesis and surface-active agents for the formation of faceted microcrystals. Due to its reducing properties, truncated β-Ag₂MoO₄@Ag octahedra are obtained in DEG. The synthesis in DMSO allows avoiding the formation of elemental silver and results in β-Ag₂MoO₄ cubes and cuboctahedra. Due to its band gap of 3.2 eV, photocatalytic activation of β-Ag₂MoO₄ is only possible under UV-light. To enable β-Ag₂MoO₄ for absorption of visible light, silver-coated β-Ag₂MoO₄@Ag and Ag₂(Mo_0.95Cr_0.05)O₄ with partial substitution of [MoO₄]²⁻ by [CrO₄]²⁻ were prepared, too. The photocatalytic activity of all the faceted microcrystals (truncated octahedra, cubes, cuboctahedra) and compositions (β-Ag₂MoO₄, β-Ag₂MoO₄@Ag, β-Ag₂(Mo_0.95Cr_0.05)O₄) is compared with regard to the photocatalytic decomposition of rhodamine B and the influence of the respective faceting, composition and wavelength.

Faceted β-Ag₂MoO₄ microcrystals are prepared by controlled nucleation and growth in diethylene glycol (DEG) or dimethylsulfoxide (DMSO).

Nanostructured Ternary Metal Tungstate-Based Photocatalysts for Environmental Purification and Solar Water Splitting: A Review

Visible-light-responsive ternary metal tungstate (MWO₄) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost, eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron-hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO₄-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO₄-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalytic activities of MWO₄-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO₄-based photocatalysts.