Traditional homogeneous Fenton reactions can only be carried out under acidic conditions; however, visible light can greatly enhance the activity and stability of iron-doped semiconductor catalysts ...in the Fenton system. Therefore, in this study, a commercially applicable Fe/graphitic carbon nitride (g-C3N4)/kaolinite composite photocatalyst was prepared for the first time using an in-situ calcination process. The results showed that Fe ions and g-C3N4 were successfully loaded onto kaolinite with a two-dimensional uniform sheet structure. The as-synthesized Fe/g-C3N4/kaolinite composite containing 0.9 mmol of Fe (Fe/CN/K-0.9) showed a degradation efficiency of 89% for tetracycline hydrochloride (TCH) within 80 min in the photo-Fenton system. Compared with photocatalytic degradation (29.6%) and Fenton degradation (76.6%), a photo-Fenton degradation efficiency of 85% was maintained after three cycles. Free radical scavenging experiments also showed that hydroxyl radicals were the main active substances. The enhanced photocatalytic activity of the composite was attributed to the large specific surface area of kaolinite, which could effectively adsorb TCH. Furthermore, FeIII acted as a photo-generated electron acceptor, which not only avoided photo-generated electron-hole recombination but also effectively reduced the consumption of H2O2 to realize a stable FeII/FeIII cycle reaction, thus improving photo-Fenton catalytic activity.
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•A kaolinite composite photocatalyst was prepared using in-situ calcination process.•Kaolinite can significantly improve the adsorption performance of g-C3N4.•Fe3+ can act as a photo-generated electron acceptor.•The photo-Fenton reaction mechanism for the kaolinite composites was proposed.
Layered nanodisks with confined thickness and lateral size have been emerging as a unique type of two‐dimensional (2D) nanomaterials in recent years. Inheriting some properties of 2D nanosheets and ...meanwhile possessing the size‐confinement effect, these layered nanodisks exhibit unique optical, electronic, and chemical properties, which endow them with great promise in a wide range of applications. Here, the recent progress of layered nanodisks is introduced. The synthetic strategies, assembly, structural/compositional transformation, and applications of layered nanodisks are systematically described and discussed, with emphasis on their new appealing structures and functions. Finally, some perspectives and future research directions of this promising field are given.
Layered nanodisks with confined thickness and lateral size are emerging as a unique type of 2D nanomaterial. The recent progress in layered nanodisks, including synthetic strategies, assembly, structural/compositional transformation, and applications are discussed.
This article discusses the synthesis, characteristics and photocatalytic mechanism of different kinds of kaolinite composite photocatalysts in detail. The latest progress of kaolinite-based ...photocatalytic materials in the fields of environment and energy is reviewed. On the basis of analyzing and discussing the limiting factors of composite photocatalyst performance, some ideas on the future development direction of this field are put forward.
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The composite catalytic materials based on the mineral kaolinite are considered to be a potential approach for solving global energy scarcity and environmental pollution, which have excellent catalytic performance, low cost and excellent chemical stability. However, pure kaolinite does not have visible light absorption ability and cannot be used as a potential photocatalytic material. Fortunately, the unique physical and chemical properties of kaolinite can be acted as a good semiconductor carrier. Herein, this paper firstly presents the mineralogical characteristics of kaolinite. Next, kaolinite-based photocatalysts (such as TiO2/kaolinite, g-C3N4/kaolinite, g-C3N4/TiO2/kaolinite, ZnO) are discussed in detail from the formation of heterostructures, synthesis-modification methods, photocatalytic mechanisms, and electron transfer pathways. Furthermore, the specific role of kaolinite in photocatalytic materials is summarized and discussed. In addition, the photocatalytic applications of kaolinite-based photocatalysts in the fields of water decomposition, pollutant degradation, bacterial disinfection are reviewed. However, the modification of kaolinite is hard, the manufacture of a large number of kaolinite-based photocatalysts is difficult, the cost of doping noble metals is expensive, and the utilization rate of visible light is low, which limits its application in industrial practice. Finally, this paper presents some perspectives on the future development of kaolinite-based photocatalysts.
Similar to heterostructures composed of different materials, possessing unique properties due to the synergistic effect between different components, the crystal‐phase heterostructures, one variety ...of hetero‐phase structures, composed of different crystal phases in monometallic nanomaterials are herein developed, in order to explore crystal‐phase‐based applications. As novel hetero‐phase structures, amorphous/crystalline heterostructures are highly desired, since they often exhibit unique properties, and hold promise in various applications, but these structures have rarely been studied in noble metals. Herein, via a one‐pot wet‐chemical method, a series of amorphous/crystalline hetero‐phase Pd nanosheets is synthesized with different crystallinities for the catalytic 4‐nitrostyrene hydrogenation. The chemoselectivity and activity can be fine‐tuned by controlling the crystallinity of the as‐synthesized Pd nanosheets. This work might pave the way to preparing various hetero‐phase nanostructures for promising applications.
Amorphous/crystalline heterophase Pd nanosheets exhibit crystallinity‐dependent chemoselectivity and catalytic activity.
Heterostructured, including heterophase, noble-metal nanomaterials have attracted much interest due to their promising applications in diverse fields. However, great challenges still remain in the ...rational synthesis of well-defined noble-metal heterophase nanostructures. Herein, we report the preparation of Pd nanoparticles with an unconventional hexagonal close-packed (2H type) phase, referred to as 2H-Pd nanoparticles, via a controlled phase transformation of amorphous Pd nanoparticles. Impressively, by using the 2H-Pd nanoparticles as seeds, Au nanomaterials with different crystal phases epitaxially grow on the specific exposed facets of the 2H-Pd, i.e., face-centered cubic (fcc) Au (fcc-Au) on the (002)h facets of 2H-Pd while 2H-Au on the other exposed facets, to achieve well-defined fcc-2H-fcc heterophase Pd@Au core–shell nanorods. Moreover, through such unique facet-directed crystal-phase-selective epitaxial growth, a series of unconventional fcc-2H-fcc heterophase core–shell nanostructures, including Pd@Ag, Pd@Pt, Pd@PtNi, and Pd@PtCo, have also been prepared. Impressively, the fcc-2H-fcc heterophase Pd@Au nanorods show excellent performance toward the electrochemical carbon dioxide reduction reaction (CO2RR) for production of carbon monoxide with Faradaic efficiencies of over 90% in an exceptionally wide applied potential window from −0.9 to −0.4 V (versus the reversible hydrogen electrode), which is among the best reported CO2RR catalysts in H-type electrochemical cells.
Nature not only carefully prepares ingenious raw materials but also continuously inspires and guides human beings to create a wide variety of intelligent materials. As the most abundant mineral ...resource on earth, clay minerals are no longer synonymous with ceramics and cements. Many natural clay minerals can be exfoliated into single‐ or few‐layered nanosheets with exquisite physicochemical properties, which can be reassembled into functional membranes with a macroscopic controllable size and microscopic ordered structure. They are thus used in many fields including chemistry, biology, energy, and environmental science. Strategic design represents one of the key processes to enhance the value of clay minerals and broaden their applications. In this work, the three frequently used approaches of exfoliation are highlighted and the six routes of assembly including casting, dip‐coating, spray coating, vacuum filtration, electrophoretic deposition, and 3D printing are compared. The corresponding principles and advantages are summarized. Representative applications of clay‐based multifunctional membranes in protection, separation, responsiveness, flexible electronics, and energy conversion are presented. The challenges and future perspectives of the clay‐based multifunctional membranes are discussed.
Nanostructured clay‐based multifunctional membranes have found widespread application. 2D clay nanosheets with a high aspect ratio are strategically reorganized to form artificial membranes with a macroscopic controllable size and a microscopic ordered structure. Clay, as an environmentally friendly and resource‐saving raw material, has emerged as an ideal building block to assemble novel functional membranes thanks to its distinctive physicochemical properties.
Based on the analysis of limited factors in improving PEC performance of BiVO4 for water splitting, this review attempts to summarize various efforts to improve the PEC performance of BiVO4-based ...materials in the last three years, such as doping nonmetal/metal elements, depositing noble metals, constructing heterojunctions, coupling with carbon and metal-organic framework (MOF) materials.
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Photoelectrochemical (PEC) technology is considered to be a promising approach for solar-driven hydrogen production with zero emissions. Bismuth vanadate (BiVO4) is a kind of photocatalytic material with strong photoactivity in the visible light region and appropriate band gap for PEC water splitting. However, the solar-to-hydrogen efficiency (STH) of BiVO4 is far away from the 10% target needed for practical application due to its poor charge separation ability. Therefore, this review attempts to summarize the strategies for improving the photocurrent density and especially hydrogen production of BiVO4 materials through PEC techniques in the last three years, such as doping nonmetal and metal elements, depositing noble metals, constructing heterojunctions, coupling with carbon and metal-organic framework (MOF) materials to further enhance the PEC performance of BiVO4 photoanode. This review aims to serve as a general guideline to fabricate highly efficient BiVO4-based materials for PEC water splitting.
Mineralogy differences in clastic sediments have a major impact on the diagenetic pathway and the evolution of pore systems between various lithofacies during burial. There is, however, a lack of ...studies on shale diagenesis since fine-grained particles are difficult to image and observe directly. Here, a quantitative method by pore counting was performed on the Wufeng-Longmaxi shale from Sichuan Basin, China with siliceous, argillaceous, and calcareous lithofacies, which makes it ideal for studying the impact of diagenesis on pore systems in different lithofacies experiencing the same burial history. The siliceous shale was formed under the anoxic reducing conditions, while argillaceous and calcareous shales were formed under dysoxic-to-oxic conditions. Authigenic quartz, of mostly biogenic origin, accounts for about 60% and 12% of the total quartz content in siliceous and calcareous shales, respectively, whereas it in argillaceous shale is almost detrital origin. The typical diagenetic sequence has the following order: compaction, cementation, clay transformation, dissolution, and organic matter (OM) maturation and its accompanying migrated OM filling. The quantitative calculation reveals that the initial porosity rapidly declines owing to compaction and cementation, while dissolution and OM maturation increase porosity to some extent. Specifically, the dominant factor resulting in porosity reduction varies in different lithofacies, which is quartz cementation and compaction for siliceous and argillaceous shales, respectively, and is both cementation (mainly quartz and carbonates) and compaction for calcareous shales. Additionally, the matrix composition controls the dominant diagenetic events in different lithofacies during the eogenetic (early diagenetic) stage, as indicated by the cementation of authigenic quartz for siliceous and compaction of ductile clays for argillaceous shales. Overall, diagenesis determines the final status of the initial pore space during the mesogenetic (middle diagenetic) stage, which further controls the abundance and distribution of migrated OM, and thus the development of the dominant OM pores in the entire pore spectrum.
•Diagenetic pathways for different Wufeng-Longmaxi shale lithofacies were studied.•A method by point counting was established to assess diagenesis controls on porosity.•Main factors resulting in porosity reduction vary in different lithofacies.•Different lithofacies show varied diagenetic pathways and porosity evolutions.
Inspired by the unique properties of ultrathin 2D nanomaterials and excellent catalytic activities of noble metal nanostructures for renewable fuel cells, a facile method is reported for the ...high‐yield synthesis of ultrathin 2D PdCu alloy nanosheets under mild conditions. Impressively, the obtained PdCu alloy nanosheet after being treated with ethylenediamine can be used as a highly efficient electrocatalyst for formic acid oxidation. The study implicates that the rational design and controlled synthesis of an ultrathin 2D noble metal alloy may open up new opportunities for enhancing catalytic activities of noble metal nanostructures.
Ultrathin PdCu alloy nanosheets are synthesized via a facile wet‐chemistry method. These nanosheets after being treated with ethylenediamine exhibit superior electrocatalytic activity toward formic acid oxidation.
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