Facile synthesis and shape evolution of well-defined phosphotungstic acid potassium nanocrystals as a highly efficient visible-light-driven photocatalyst

Phase-Controlled Multi-Dimensional-Structure SnS/SnS2/CdS Nanocomposite for Development of Solar-Driven Hydrogen Evolution Photocatalyst

The quest for water-splitting photocatalysts to generate hydrogen as a clean energy source from two-dimensional (2D) materials has enormous implications for sustainable energy solutions. Photocatalytic water splitting, a major field of interest, is focused on the efficient production of hydrogen from renewable resources such as water using 2D materials. Tin sulfide and tin disulfide, collectively known as SnS and SnS2, respectively, are metal sulfide compounds that have gained attention for their photocatalytic properties. Their unique electronic structures and morphological characteristics make them promising candidates for harnessing solar energy for environmental and energy-related purposes. CdS/SnS/SnS2 photocatalysts with two Sn phases (II and IV) were synthesized using a solvothermal method in this study. CdS was successfully placed on a broad SnS/SnS2 plane after a series of characterizations. We found that it is composited in the same way as a core-shell shape. When the SnS/SnS2 phase ratio was dominated by SnS and the structure was composited with CdS, the degradation efficiency was optimal. This material demonstrated high photocatalytic hydrogenation efficiency as well as efficient photocatalytic removal of Cr(VI) over 120 min. Because of the broad light absorption of CdS, the specific surface area, which is the reaction site, became very large. Second, it served as a transport medium for electron transfer from the conduction band (CB) of the SnS to the CB of the SnS2. Because of the composite, these electrons flowed into the CB of CdS, improving the separation efficiency of the photogenerated carriers even further. This material, which was easily composited, also effectively prevented mineral corrosion, which is a major issue with CdS.

Three-dimensional nano assembly of nickel cobalt sulphide/polyaniline@polyoxometalate/reduced graphene oxide hybrid with superior lithium storage and electrocatalytic properties for hydrogen evolution reaction

Engineering hierarchical nanostructures with enhanced charge storage capacity and electrochemical activity are vital for the advancement of energy devices. Herein, a highly ordered mesoporous three-dimensional (3D) nano-assembly of Nickel Cobalt Sulphide/Polyaniline @Polyoxometalate/Reduced Graphene Oxide (NiCo₂S₄/PANI@POM/rGO) is prepared first time via a simple route of oxidative polymerization followed by a hydrothermal method. Morphological analysis of the resulting hybrid reveals the sheet-like structures containing a homogeneous assembly of PANI@POM and NiCo₂S₄ on the graphene exterior maintaining huge structural integrity, large surface area and electrochemically active centres. The electrochemical analysis of the nanohybrid as the anode of the lithium-ion battery (LIB) has delivered ultra-huge reversible capacity of 735.5 mA h g^-1 (0.1 A g^-1 after 200 cycles), superb capacity retention (0.161% decay/per cycle at 0.5 A g^-1 for 1000 cycles), and significant rate capability (355.6 mA h g^-1 at 2 A g^-1). The hydrogen evolution reaction (HER) measurement also proves remarkable activity, extremely low overpotential and high durability. The extraordinary performance of the nanohybrid is due to the presence of abundant electroactive centres, high surface area and a large number of ion exchange channels. These outstanding results prove the advantages of a combination of NiCo₂S₄, graphene sheets, and PANI@POM in energy devices.

Organic–inorganic hybrid phosphite-participating S-shaped penta-CeIII incorporated tellurotungstate as electrochemical enzymatic hydrogen peroxide for β-D-glucose detection

Polyoxometalate chemistry has made rapid advances in innovative structural chemistry. The lower valence state and lone electron pair effect of subgroup-valence heteroatom Te(IV) can be introduced into the tungsten-oxygen system...

Application of polyoxometalates in photocatalytic degradation of organic pollutants

Organic pollutants are highly toxic, accumulative, and difficult to degrade or eliminate. As a low-cost, high-efficiency and energy-saving environmental purification technology, photocatalytic technology has shown great advantages in solving increasingly serious environmental pollution problems. The development of efficient and durable photocatalysts for the degradation of organic pollutants is the key to the extensive application of photocatalysis technology. Polyoxometalates (POMs) are a kind of discrete metal-oxide clusters with unique photo/electric properties which have shown promising applications in photocatalytic degradation. This review summarizes the recent advances in the design and synthesis of POM-based photocatalysts, as well as their application in the degradation of organic dyes, pesticides and other pollutants. In-depth perspective views are also proposed in this review.

Cadmium sulfide quantum dots/dodecahedral polyoxometalates/oxygen-doped mesoporous graphite carbon nitride with Z-scheme and Type-II as tandem heterojunctions for boosting visible-light-driven photocatalytic performance

It is known that fabrication of tandem heterojunctions between different types of heterojunctions can promote the charge separation. Herein, novel cadmium sulfide quantum dots (CdS QDs)/dodecahedral phosphotungstic acid potassium K₃PW₁₂O₄₀ (KPW)/oxygen-doped mesoporous graphite carbon nitride (meso-g-C₃N₄) nanosheets tandem heterojunctions are prepared by the hydrothermal method combined with direct template calcination and in-situ chemical sedimentation strategy. The results show that tandem heterojunctions formed by the Z-Scheme heterojunction between CdS QDs and KPW and the type-II heterojunction between CdS QDs and meso-g-C₃N₄ can extend the optical response into visible light region. Importantly, under visible light irradiation, photocatalytic hydrogen production rate and photocatalytic Cr⁶⁺ removal rate over CdS/KPW/meso-g-C₃N₄ is higher than that of KPW and CdS/KPW. This remarkable photocatalytic performance is due to the effective charge separation and transfer of the special tandem heterojunction structure. This novel tandem heterojunction will offer new insights for fabricating other high-performance photocatalytic systems.

Polymeric Thermoelectric Composites by Polypyrrole and Cheap Reduced Graphene Oxide in Towel-Gourd Sponge Fibers

The thermoelectric (TE) materials can transform thermal energy into electrical energy, and polymer TE composites have attracted increasing interest for flexible semiconductors. However, polymer composites suffer from low TE performances due to the low electroconductibility (σ). Herein, grafted conducting networks were fabricated by grafting polypyrrole (PPy) onto the cheap graphene of reduced graphene oxide (rGO) in the bundled micro-tunnel of towel-gourd sponge (TS) fibers. Afterward, the TS powders containing grafted conducting networks were cured by the polydimethylsiloxane (PDMS). The PDMS/TS-rGO-PPy composites exhibited an σ of 74 S/m, thermal conductivity of 0.249 W·m-1·K-1, Seebeck coefficient of 84.2 μV/K, and thermoelectric figure of merit of 5.427 × 10-4 with 10.0 wt % filler loading. Moreover, dynamic TE properties of our composites under tensile loading were investigated. The results show that the grafted conducting network maintained its integrity by interconnection of PPy between adjacent rGO nano-layers.

Synthesis of micro/nanoscaled metal–organic frameworks and their direct electrochemical applications

Developing strategies to control the morphology and size of MOFs is important for their applications in batteries, supercapacitors and electrocatalysis. This review focuses on the design and fabrication of MOFs at the micro/nanoscale.

The comparative study of two reusable phosphotungstic acid salts/reduced graphene oxides composites with enhanced photocatalytic activity

In this work, two recyclable phosphotungstic acid salts/reduced graphene oxides were successfully prepared. The prepared samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), Raman spectroscopy, and photoluminescence spectroscopy (PL). The structure and catalytic performance of two composites were comparatively investigated, and the reduced graphene oxide mass ratios in K₃[PW₁₂O₄₀]/reduced graphene oxide (denoted as KPW-RGO) and (NH₄)₃[PW₁₂O₄₀]/reduced graphene oxide (denoted as NH₄PW-RGO) were optimized and their roles in them were explored. The results indicate that the Keggin structures of KPW and NH₄PW are still kept after being anchored on the RGO surface, but their morphologies change a lot in composites. The photocatalytic activities of KPW-3RGO (0.01989 min^-1) are 5.42 times than that of KPW (0.00367 min^-1), and NH₄PW-1RGO (0.0184 min^-1) is 2.26 times than that of NH₄PW (0.00814 min^-1). The enhanced photocatalytic activity is mainly ascribed to photo-induced interfacial charge transfer on the heterojunction between RGO and NH₄PW or KPW and strong adsorption ability of RGO towards MO. Moreover, NH₄PW-1RGO and KPW-3RGO had much better photocatalytic activity, good recyclable ability, and stability compared to HPW-RGO, which cannot be recycled.

In-situ green assembly of spherical Mn-based metal-organic composites by ion exchange for efficient electrochemical oxidation of organic pollutant

In this study, we develop a facile ion exchange strategy for in-situ assembly of novel spherical metal-organic composites on a large scale. The functional groups (-NH₂, -COOH and -SO₃H) on chelating and exchange resins had significant effects on improving uniform distribution of metallic sites and metal-support interaction. Without any addition of H₂O₂, Mn-based metal-organic composites realized the recovery of waste metallic ions and exhibited high activity for methylene blue (MB) electro-Fenton degradation (97.8% decoloration and 54.7% TOC removal) within 150 min under low current density (7.53 mA·cm^-2) and 3.0 g·L^-1 catalyst dosage. Analyses of performance on different active sites (Fe^II, Mn^II, Co^II, Ce^III and Cu^II) and supports clearly indicated that synergetic effect of Mn^II and organic supports played crucial roles in electrochemical oxidation. Kinetic rate constant of 0.037 min^-1 and turn over frequency of 0.23 h^-1 were much better than those of inorganic supported catalysts, which were attributed to intramolecular electron transfer greatly accelerating Mn^II/Mn^III autocatalytic cycle. Meanwhile, possible degradation pathway of MB was proposed by analysis of oxidative intermediate products. Benefiting from excellent properties and millimeter-level size structure, metal-organic composites can be applied in wide pH range of 2.0-9.0 and easily separated in the industrial application.

Controlled Synthesis of Hollow α-Fe2O3 Microspheres Assembled With Ionic Liquid for Enhanced Visible-Light Photocatalytic Activity

Porous self-assembled α-Fe₂O₃ hollow microspheres were fabricated via an ionic liquid-assisted solvothermal reaction and sequential calcinations. The concentration of the ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate [C₄Mim]BF₄) was found to play a crucial role in the control of these α-Fe₂O₃ hollow structures. Trace amounts ionic liquid was used as the soft template to synthesize α-Fe₂O₃ hollow spheres with a large specific surface (up to 220 m²/g). Based on time-dependent experiments, the proposed formation mechanisms were presented. Under UV light irradiation, the as-synthesized α-Fe₂O₃ hollow spheres exhibited excellent photocatalysis in Rhodamine B (RhB) photodegradation and the rate constant was 2–3 times higher than α-Fe₂O₃ particles. The magnetic properties of α-Fe₂O₃ hollow structures were found to be closely associated with the shape anisotropy.

Synthesis and Progress of New Oxygen-Vacant Electrode Materials for High-Energy Rechargeable Battery Applications

During the last few years, a great amount of oxygen-vacant materials have been synthetized and applied as electrodes for electrochemical storage. The presence of oxygen vacancies leads to an increase in the conductivity and the diffusion coefficient; consequently, the controllable synthesis of oxygen vacancy plays an important role in improving the electrochemical performance, including achieving high specific capacitance, high power density, high energy density, and good cycling stability of the electrode materials for batteries. This review mainly focuses on research progress in the preparation of oxygen-vacant nanostructures and the application of materials with oxygen vacancies in various batteries (such as lithium-ion, lithium-oxygen, and sodium-ion batteries). Challenges related to and opportunities for oxygen-vacant materials are also provided.

A Series of Compounds Based on [P2W18O62]6- and Transition Metal Mixed Organic Ligand Complexes with High Catalytic Properties for Styrene Epoxidation

Seven compounds based on [P₂W₁₈O₆₂]^6- ({P₂W₁₈}) were successfully prepared and carefully characterized. [HC₅H₅N][Cu(2,2'-bpy)₂]₂[HP₂W₁₈O₆₂]·2H₂O (bpy = bipyridine) (1) is constructed from {P₂W₁₈} bridged by [Cu(2,2'-bpy)₂]²⁺. [HC₅H₅N][Zn(2,2'-bpy)₂]₂[HP₂W₁₈O₆₂]·4H₂O (1a) is isostructural and isomorphous with compound 1. [Cu₄(2,2'-bpy)₃(nic)₃(OH)₂(H₂O)][H₃P₂W₁₈O₆₂]·0.5H₂O (nic = nicotinic acid) (2) is formed by {P₂W₁₈} and tetracopper transition metal mixed organic ligand complexes (TMMCs). [Cu₂(2,2'-bpy)₂(C₂O₄)]₃[P₂W₁₈O₆₂]·3H₂O (3) is made up of {P₂W₁₈} and bicopper TMMCs, [Cu₆(2,2'-bpy)₆(OH)₆][P₂W₁₈O₆₂]·2H₂O (4) is built up from {P₂W₁₈}, and hexacopper complexes of 2,2'-bpy and hydroxyls. [Cu(2,2'-bpy)(hnic)_0.5][Cu₃(2,2'-bpy)₃(hnic)₂(H₂O)₂][H₃P₂W₁₈O₆₂] (hnic = hydroxyl nicotinic acid) (5a) contains two different TMMCs. In addition, compound 5a is the first example of a compound that contains Cu-π interactions. [Cu₂(2,2'-bpy)₂(hnic)][H₄P₂W₁₈O₆₂]· xH₂O ( x ≈ 50) (5b) is based on {P₂W₁₈} and [Cu₂(2,2'-bpy)₂(hnic)]²⁺. We discuss the mechanisms for the formations of these compounds. All the catalytic performances of the compounds for styrene epoxidation to styrene oxide are high.

Recent Progress in Some Amorphous Materials for Supercapacitors

A breakthrough in technologies having "green" and sustainable energy storage conversion is urgent, and supercapacitors play a crucial role in this area of research. Owing to their unique porous structure, amorphous materials are considered one of the best active materials for high-performance supercapacitors due to their high specific capacity, excellent cycling stability, and fast charging rate. This Review summarizes the synthesis of amorphous materials (transition metal oxides, carbon-based materials, transition metal sulfides, phosphates, hydroxides, and their complexes) to highlight their electrochemical performance in supercapacitors.

FeO x -Based Materials for Electrochemical Energy Storage

Iron oxides (FeO x ), such as Fe2O3 and Fe3O4 materials, have attracted much attention because of their rich abundance, low cost, and environmental friendliness. However, FeO x , which is similar to most transition metal oxides, possesses a poor rate capability and cycling life. Thus, FeO x -based materials consisting of FeO x , carbon, and metal-based materials have been widely explored. This article mainly discusses FeO x -based materials (Fe2O3 and Fe3O4) for electrochemical energy storage applications, including supercapacitors and rechargeable batteries (e.g., lithium-ion batteries and sodium-ion batteries). Furthermore, future perspectives and challenges of FeO x -based materials for electrochemical energy storage are briefly discussed.

Template-Free Preparation of 3D Porous Co-Doped VN Nanosheet-Assembled Microflowers with Enhanced Oxygen Reduction Activity

Developing cheap and stable electrocatalysts is considered the key factor to achieve the large-scale application of fuel cells. In this paper, three-dimensional (3D) porous Co-doped vanadium nitride (VN) nanosheet-assembled microflowers are prepared with a facile solvothermal approach followed by nitridation at 500 °C in NH₃. It is found that the microflower morphology and the Co doping both significantly enhance the oxygen reduction reaction (ORR) performance of the materials. Because the unique 3D porous structure provides higher specific surface area and more active sites as well as enriching the d electrons of V via doping, Co also improves the intrinsic activity of VN. Our optimal V_0.95Co_0.05N microflowers achieve a half-wave potential for the ORR of up to 0.80 V in 0.1 M KOH solution, which is almost comparable to that of commercial 20% Pt/C. More importantly, the catalysts show superior durability with little current decline (less than 12%) during chronoamperometric evaluation for over 25 000 s. These features make the V_0.95Co_0.05N microflowers attractive for fuel cell applications.

Graphene blended with SnO2 and Pd-Pt nanocages for sensitive non-enzymatic electrochemical detection of H2O2 released from living cells

This paper described a novel, facile and nonenzymatic electrochemical biosensor to detect hydrogen peroxide (H₂O₂). The sensor was fabricated based on Pd-Pt nanocages and SnO₂/graphene nanosheets modified electrode (PdPt NCs@SGN/GCE). The electrochemical behavior of PdPt NCs@SGN/GCE exhibited excellent catalytic activity toward H₂O₂ with fast response, high selectivity, superior sensitivity, low detection limit of 0.3 μM and large linear range from 1 μM to 300 μM. Under these obvious advantages, the constructed biosensor provided to be reliable for determination of H₂O₂ secreted from human cervical cancer cells (Hela cells). Hence, the proposed biosensor is a promising candidate for detection of H₂O₂ in situ released from living cells in clinical diagnostics.

One dimensional hierarchical nanostructures composed of CdS nanosheets/nanoparticles and Ag nanowires with promoted photocatalytic performance

One dimensional Ag@CdS core–shell hierarchical nanostructures with excellent photocatalytic performance have been fabricated via a simple wet-chemistry approach at low temperature.

Intrinsic peroxidase-like activity and enhanced photo-Fenton reactivity of iron-substituted polyoxometallate nanostructures

Fe-substituted heteropolyacid nanostructures are developed for the efficient degradation of pollutants via Fenton and photo-Fenton reactions and show efficient artificial enzyme-like activity for oxidation.

Z-scheme Ag3PO4/POM/GO heterojunction with enhanced photocatalytic performance for degradation and water splitting

To develop solar light-driven photocatalysts with high activity and structural stability, Ag₃PO₄/POM/GO heterojunction has been successfully prepared by a facile method at room temperature.

Metal (M = Co, Ni) phosphate based materials for high-performance supercapacitors

With the ever increasing demand for clean, sustainable energy, electrochemical supercapacitors with the advantages of high power density, high efficiency and long life expectancy have become one of the major devices for energy storage and power supply, and have found wide application in hybrid power sources, backup power sources, starting power for fuel cells and burst-power generation in electronic devices.

Crystal Engineering in Supramolecular Polyoxometalate Hybrids through pH Controlled in Situ Ligand Hydrolysis

A family of five different three-dimensional polyoxometalate (POM) based supramolecular hybrids were synthesized by a hydrothermal route under different pH using a hydrolyzable naphthalene diimide ligand. The mechanism of crystallographic phase variation of the POM-amino pyridine hybrids under different pH was studied through controlled experiments where the final hydrolyzed products were analyzed through NMR and single crystal X-ray diffraction. Different pH conditions led to variation in the extent of protonation and hydrolyzation of the ligand, yielding different phases. All of these were identified, and the structures of the supramolecular hybrids were characterized extensively. Mechanistic study proved that only the reaction conditions are responsible for the hydrolysis of the ligand and the in situ generated POM species do not have any role in it. Magnetic measurements confirmed the hexavalent oxidation states of the transition metal center (Mo) in the POM. Optical band gap measurements revealed that these hybrids are semiconducting in nature. Two of the compounds were studied for hydrogen peroxide mediated selective oxidation catalysis of small organic molecules and found to exhibit very good activity with high percentage of selectivity for the desired products of industrial importance.

Fabrication of Metal Molybdate Micro/Nanomaterials for Electrochemical Energy Storage

Currently, metal molybdates compounds can be prepared by several methods and are considered as prospective electrode materials in many fields because the metal ions possess the ability to exist in several oxidation states. These multiple oxidation states contribute to prolonging the discharge time, improving the energy density, and increasing the cycling stability. The high electrochemical performance of metal molybdates as electrochemical energy storage devices are discussed in this review. According to recent publications and research progress on relevant materials, the investigation of metal molybdate compounds are discussed via three main aspects: synthetic methods, material properties and measured electrochemical performance of these compounds as electrode materials. The recent progress in general metal molybdate nanomaterials for LIBs and supercapacitors are carefully presented here.

Nickel Hydroxide Supercapacitor with a Theoretical Capacitance and High Rate Capability Based on Hollow Dendritic 3D-Nickel Current Collectors

A straightforward way to attain the theoretical capacitance and high rate capability of nickel hydroxide supercapacitors, by utilizing a mesoporous hollow dendritic three-dimensional-nickel (3D-Ni) current collector is proposed. A facile electrodeposition method employing a hydrogen bubble template was chosen for rapid fabrication of the dendritic 3D-nickel structure. After nickel hydroxide was deposited on the hollow 3D-nickel current collector, it exhibited a highest capacitance of 3637 F g^-1 at a current density of 1 A g^-1 , and retained 97 % of capacitance at a high current density of 100 A g^-1 with a cycle stability of over 80 % after 10 000 cycles. The enhanced performance could be attributed to the large surface area and high conductivity of the moss-like dendritic 3D-Ni current collector, which allowed direct contact between the active materials and the current collector, and reduced diffusion resistance between the surface of the active materials and the electrolyte. These results not only confirmed a facile fabrication method for high-performance 3D metal nanostructures, but also offer a promising solution for state-of-the-art energy storage systems.

Growth mechanism of ceria nanorods by precipitation at room temperature and morphology-dependent photocatalytic performance

Ceria (CeO₂) nanorods have been prepared by simple short-term precipitation at room temperature for the first time.

Construction of (3,6)-connected polyoxometalate-based metal–organic frameworks (POMOFs) from triangular carboxylate and dimerized Zn4-ε-Keggin

The methodology of extension of reduced transition metal-grafted ε-Keggin polyoxoanions with two types of terphenyl-based tricarboxylates was used to isolate two (3,6)-connected 3D POMOFs.

Three dimensional Ni1+xFe2−xS4-graphene-2D-MoSe2 as an efficient material for supercapacitors

A ternary Ni_1+xFe_2−xS₄-graphene-2D-MoSe₂ (Ni_1+xFe_2−xS₄-g-MoSe₂) nanocomposite was designed and fabricated through a facile two-step method.