Electrocatalytic water splitting into H2 and O2 is a key technology for carbon‐neutral energy. Here, we report a modular materials design leading to noble metal‐free composite electrocatalysts, which ...combine high electrical conductivity, high OER and HER reactivity and high durability. The scalable bottom‐up fabrication allows the stable deposition of mixed metal oxide nanostructures with different functionalities on copper foam electrodes. The composite catalyst shows sustained OER and HER activity in 0.1 m aqueous KOH over prolonged periods (t>10 h) at low overpotentials (OER: ≈300 mV; HER: ≈100 mV) and high faradaic efficiencies (OER: ≈100 %, HER: ≈98 %). The new synthetic concept will enable the development of multifunctional, mixed metal oxide composites as high‐performance electrocatalysts for challenging energy conversion and storage reactions.
Efficient electrochemical water splitting is achieved by hydrothermal deposition of a bifunctional mixed metal oxide electrocatalyst on copper foam electrodes. Individual metal oxide components are chosen for catalytic activity, electrical conductivity, and structural/chemical stability. The modular synthesis based on molecular precursors could lead to a new class of multifunctional catalysts for challenging energy conversion and storage reactions.
The hierarchical aggregation of molecular nanostructures from multiple components is a grand synthetic challenge, which requires highly selective linkage control. We demonstrate how two orthogonal ...linkage groups, that is, organotin and lanthanide cations, can be used to drive the aggregation of a giant molecular metal oxide superstructure. The title compound {(Sn(CH3)2)2O4{CeW5O18 TeW4O16CeSn(CH3)24TeW8O314}2}46− (1 a) features dimensions of ca. 2.2×2.3×3.4 nm3 and a molecular weight of ca. 25 kDa. Structural analysis shows the hierarchical aggregation from several independent subunits. Initial biomedical tests show that 1 features an inhibitory effect on the proliferation of HeLa cells based on an apoptosis pathway. In vivo experiments in mice reveal the antiproliferative activity of 1 and open new paths for further development of this new compound class.
Hierarchical assembly of a giant heterometallic polyoxotungstate supercluster with a molecular weight of ca. 25 kDa is reported. Geometrically unrestricted cerium(III) and geometrically restricted dimethyl tin cation linkers are used to gain access to a giant molecular species featuring three different polyoxometalate building units. The compound demonstrates in vitro and in vivo antiproliferative activity against HeLa cervical cancer cell lines.
The construction of organic–inorganic hybrid supramolecular polymers using polyoxometalate (POM) as building block is expected to bring new opportunities to the functionalization of supramolecular ...polymers and the development of novel POM‐based soft materials. Here, by using the orthogonal self‐assembly based on host–guest interactions and metal‐ligand interactions, we report the in situ construction of a novel POM‐based hybrid supramolecular polymer (POM‐SP) at the oil‐water interface, while the redox and competitive responsiveness can be triggered independently. Moreover, the binding energy of POM‐SP at the interface is sufficiently strong so that the assembly of POM‐SP jams, allowing the stabilization of liquids in nonequilibrium shapes, offering the possibility of fabricating all‐liquid constructs with reconfigurability.
A simple and efficient strategy is developed to prepare polyoxometalate‐based hybrid supramolecular polymers (POM‐SPs) by interfacial orthogonal self‐assembly. Owing to the dynamic nature of noncovalent interactions, POM‐SP‐based interfacial assemblies with redox or competitive agent responsiveness can be achieved.
Novel 3D Ni1−xCoxSe2 mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni1−xCoxSe2 MNSN/NF with x ranging from 0 to 0.35). The collective effects of ...special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni0.89Co0.11Se2 MNSN/NF is revealed to exhibit an overpotential (η10) of 85 mV at −10 mA cm−2 in alkaline medium (pH 14) and η10 of 52 mV in acidic solution (pH 0), which are the best among all selenide‐based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η10 of 82 mV for all noble metal‐free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all‐pH HER activity of Ni0.89Co0.11Se2 is originated from the enhanced adsorption of both H+ and H2O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all‐pH HER electrocatalysts.
An integrated electrocatalyst comprising 3D mesoporous Ni0.89Co0.11Se2 nanosheet networks on Ni foam is synthesized, and it demonstrates very high activities and excellent stabilities for hydrogen evolution reaction (HER) in all‐pH conditions. Theoretical calculations verify that electronic structure engineering by optimal Co doping enhances the adsorption of H+ and H2O, leading to the advanced all‐pH HER activity of the catalyst.
Although progress has been made to improve photocatalytic CO2 reduction under visible light (λ>400 nm), the development of photocatalysts that can work under a longer wavelength (λ>600 nm) remains a ...challenge. Now, a heterogeneous photocatalyst system consisting of a ruthenium complex and a monolayer nickel‐alumina layered double hydroxide (NiAl‐LDH), which act as light‐harvesting and catalytic units for selective photoreduction of CO2 and H2O into CH4 and CO under irradiation with λ>400 nm. By precisely tuning the irradiation wavelength, the selectivity of CH4 can be improved to 70.3 %, and the H2 evolution reaction can be completely suppressed under irradiation with λ>600 nm. The photogenerated electrons matching the energy levels of photosensitizer and m‐NiAl‐LDH only localized at the defect state, providing a driving force of 0.313 eV to overcome the Gibbs free energy barrier of CO2 reduction to CH4 (0.127 eV), rather than that for H2 evolution (0.425 eV).
The selectivity of CH4 reached 70.3 % and the by‐product H2 was completely suppressed by monolayer‐NiAl‐LDH in CO2 photoreduction under irradiation with λ>600 nm. The defect state in monolayer‐NiAl‐LDH plays an important role in the outstanding selectivity by localizing the photogenerated electrons excited by photons with λ>600 nm.
The exploration of high nuclearity molecular metal oxide clusters and their reactivity is a challenge for chemistry and materials science. Herein, we report an unprecedented giant molecular ...cerium–bismuth tungstate superstructure formed by self‐assembly from simple metal oxide precursors in aqueous solution. The compound, {W14CeIV6O61(W3Bi6CeIII3(H2O)3O14B‐α‐BiW9O333)2}34− was identified by single‐crystal X‐ray diffraction and features 104 metal centers, a relative molar mass of ca. 24 000 and is ca. 3.0×2.0×1.7 nm3 in size. The cluster anion is assembled around a central {Ce6} octahedron which is stabilized by several molecular metal oxide shells. Six trilacunary Keggin anions (B‐α‐BiW9O339−) cap the superstructure and limit its growth. In the crystal lattice, water‐filled channels with diameters of ca. 0.5 nm are observed, and electrochemical impedance spectroscopy shows pronounced proton conductivity even at low temperature.
A giant cerium–bismuth tungstate cluster featuring more than 100 metal ions and a relative molar mass of approximately 24 000 is structurally characterized. The cluster anions form a highly 3D‐porous crystalline lattice featuring water‐filled channels. Proton conductivity measurements show high proton mobility within the framework.
Polyoxometalates (POMs) are widely used in catalysis, energy storage, biomedicine, and other research fields due to their unique acidity, photothermal, and redox features. However, the leaching and ...agglomeration problems of POMs greatly limit their practical applications. Confining POMs in a host material is an efficient tool to address the above‐mentioned issues. POM@host materials have received extensive attention in recent years. They not only inherent characteristics of POMs and host, but also play a significant synergistic effect from each component. This review focuses on the recent advances in the development and applications of POM@host materials. Different types of host materials are elaborated in detail, including tubular, layered, and porous materials. Variations in the structures and properties of POMs and hosts before and after confinement are highlighted as well. In addition, an overview of applications for the representative POM@host materials in electrochemical, catalytic, and biological fields is provided. Finally, the challenges and future perspectives of POM@host composites are discussed.
Polyoxometalates (POMs) possess unique physiochemical properties for versatile applications. However, the leaching and agglomeration problems of POMs remain highly challenging. Confining POMs in host materials is an efficient tool to address these issues. This review summarizes recent progresses on the development and application of POM@host materials, and highlights the opportunities and challenges in fabricating and gaining insight into POM@host composites.
Crack assessment of bridge piers using unmanned aerial vehicles (UAVs) eliminates unsafe factors of manual inspection and provides a potential way for the maintenance of transportation ...infrastructures. However, the implementation of UAV‐based crack assessment for real bridge piers is hindered by several key issues, including the following: (a) both perspective distortion and the geometry distortion by nonflat structural surfaces usually appear on crack images taken by the UAV system from the pier surface; however, these two kinds of distortions are difficult to correct at the same time; and (b) the crack image taken by a close‐range inspection flight UAV system is partially imaged, containing only a small part of the entire surface of the pier, and thereby hinders crack localization. In this paper, a new image‐based crack assessment methodology for bridge piers using UAV and three‐dimensional (3D) scene reconstruction is proposed. First, the data acquisition of UAV‐based crack assessment is discussed, and the UAV flight path and photography strategy for bridge pier assessment are proposed. Second, image‐based crack detection and 3D reconstruction are conducted to obtain crack width feature pair sequences and 3D surface models, respectively. Third, a new method of projecting cracks onto a meshed 3D surface triangular model is proposed, which can correct both the perspective distortion and geometry distortion by nonflat structural surfaces, and realize the crack localization. Field test investigations of crack assessment of a real bridge pier using a UAV are carried out for illustration, validation, and error analysis of the proposed methodology.
A three dimensional problem can be approximated by either a two-dimensional
or one-dimensional case, but some information will be lost. To reveal the
lost information due to the lower dimensional ...approach, two-scale
mathematics is needed. Generally one scale is established by usage where
traditional calculus works, and the other scale is for revealing the lost
information where the continuum assumption might be forbidden, and
fractional calculus or fractal calculus has to be used. The two-scale
transform can approximately convert the fractional calculus into its
traditional partner, making the two-scale thermodynamics much promising.
nema
Recently, it has become very important to develop cost‐effective anode materials for the large‐scale use of lithium‐ion batteries (LIBs). Polyoxometalates (POMs) have been considered as one of the ...most promising alternatives for LIB electrodes owing to their reversible multi‐electron‐transfer capacity. Herein, Keggin‐type PMo12O403− (donated as PMo12) clusters are anchored onto a 3D microporous carbon framework derived from ZIF‐8 through electrostatic interactions. The PMo12 clusters can be immobilized steadily and uniformly on the carbon framework, which provides enhanced electrical conductivity and high stability. Compared with PMo12 itself, the as‐prepared novel 3D Carbon‐PMo12 composite displays a significantly improved Li‐ion storage performance as an LIB anode, with excellent reversible specific capacity and rate capacity, as well as high cycling performance (discharge capacity of 985 mA h g−1 after 200 cycles), which are superior to other POM‐based anode materials reported so far. The high performance of the Carbon‐PMo12 composite can be attributed to the 3D conductive network with fast electron transport, high ratio of pseudocapacitive contribution, and evenly distributed PMo12 clusters with reversible 24‐electron transfer capacity. This work offers a facile way to explore novel LIB anodes consisting of electroactive molecule clusters.
Polyoxometalate anode: A novel 3D Carbon‐PMo12 composite is fabricated, which displays a significantly improved Li‐ion storage performance as an anode for Li‐ion batteries, with excellent reversible specific capacity and rate capacity.
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