Direct evidence for active site-dependent formic acid electro-oxidation by topmost-surface atomic redistribution in a ternary PtPdCu electrocatalyst

The active site-dependent electrochemical formic acid oxidation was evidenced by the increased coverage of Pt in the topmost mixed PtPd alloy layer of ternary PtPdCu upon potential cycling, which demonstrated two catalytic pathways only in one catalyst owing to surface atomic redistribution in an acidic electrolyte environment

Stretchable and Self-Healing Graphene Oxide–Polymer Composite Hydrogels: A Dual-Network Design

Superior mechanical properties and self-healing are two hot topics in hydrogel science due to their tight relationship with the following potential application scopes. Most of the conventional hydrogels do not possess both features at the same time. Herein, we expand the recently proposed intertwined double-network mechanism and prepare a novel class of graphene oxide (GO)/poly­(acryloyl-6-aminocaproic acid) (PAACA) composite hydrogels with enhanced mechanical properties and self-healing capability to pH stimulus. Without the use of any conventional organic cross-linkers, the double networks in GO/PAACA hydrogels are triggered by GO nanosheets and calcium ions as cross-linkers. For one thing, Ca²⁺ induces the formation of the 3D cross-linked network through coordination interactions with both oxygen-containing groups of GO nanosheets and polar groups of PAACA side chains. For another, powerful hydrogen-bonding network is simultaneously interconnected, attributed to the interactions of polar groups of PAACA side chains with both other polar groups of PAACA side chains and oxygen-containing groups of GO nanosheets

Macroscopic Multifunctional Graphene-Based Hydrogels and Aerogels by a Metal Ion Induced Self-Assembly Process

We report a one-step fabrication of macroscopic multifunctional graphene-based hydrogels with robust interconnected networks under the synergistic effects of the reduction of graphene oxide sheets by ferrous ions and <i>in situ</i> simultaneous deposition of nanoparticles on graphene sheets. The functional components, such as α-FeOOH nanorods and magnetic Fe₃O₄ nanoparticles, can be easily incorporated with graphene sheets to assemble macroscopic graphene monoliths just by control of pH value under mild conditions. Such functional graphene-based hydrogels exhibit excellent capability for removal of pollutants and, thus, could be used as promising adsorbents for water purification. The method presented here is proved to be versatile to induce macroscopic assembly of reduced graphene sheets with other functional metal oxides and thus to access a variety of graphene-based multifunctional nanocomposites in the form of macroscopic hydrogels or aerogels

Synthesis and Optical Properties of Mesoporous beta-Co(OH)2/Brilliant Blue G (G250) Hybrid hierarchical structures

New mesoporous β-Co(OH)2/brilliant blue G (G250) hybrid hierarchical structures constructed by thin mesocrystal nanosheets can be synthesized by a one-step refluxing process under the synergistic effect of CTAB and G250. This approach opens up an avenue to access new novel inorganic/dye hybrid materials with hierarchical structures for pigment and electrocatalytic application

Templating Synthesis of Mesoporous Fe₃C‑Encapsulated Fe–N-Doped Carbon Hollow Nanospindles for Electrocatalysis

Developing cost-efficient alternatives to the noble metal catalysts toward oxygen reduction reaction (ORR) has attracted much attention. Herein, a kind of mesoporous hollow spindlelike Fe–N–C electrocatalysts with iron carbide nanoparticles encased in the N-doped graphitic layers has been synthesized by a novel “reactive hard template” strategy through the Fe³⁺-assisted polymerization of dopamine on the Fe₂O₃ cores and the following calcinations. The Fe₂O₃ nanospindles not only as the hard template guide the formation of well-defined shape and structure of the catalyst but also as the reactive template provide Fe reservoir to generate Fe₃C nanoparticles in the catalyst during the thermochemical process. The superiority in accessible active sites of Fe–N_<i>x</i> species, Fe₃C nanoparticles in graphenelike layers, and highly mesoporous hollow structure enables the catalysts to exhibit excellent ORR performances including high catalytic activity, outstanding long-term cycling stability, and good tolerance to methanol

Provenance of Eclogitic Metasediments in the North Qilian HP/LT Metamorphic Terrane, Western China: Geodynamic Implications for Early Paleozoic Subduction-Erosion

In this contribution, we present new petrological, geochemical, zircon U–Pb and Hf isotopic data for eclogitic metasediments from the north Qilian orogenic belt, in which early Paleozoic ophiolitic sequences and HP/LT metamorphic rocks have been previously recognized. The studied metasediments contain eclogite facies assemblages reflecting P–T conditions of 450–560 °C and 1.9–2.4 GPa, consistent with those of adjacent eclogites. REE compositions of the eclogitic metasediments overlap those of average upper continental crust. The SHRIMP and LA-MC-ICPMS U–Pb data of zircons from metasediments demonstrate input from sources with major age components about 500 Ma and 1600–1900 Ma (peak at ~ 1800 Ma), with a smaller population at 660–800 Ma (peak at 750 Ma), and minor \u3e 1.9 Ga zircon ages. The youngest detrital zircons suggest a maximum depositional age of ca. 475 Ma, and combined with P–T conditions and previously determined metamorphic age suggest a burial rate of \u3e 0.6–0.7 cm/yr. Zircon Hf isotopic analyses show that 500 Ma zircons have positive εHf(t) (mainly between + 8 and + 16). By contrast, Meso- to Paleoproterozoic detrital zircons show a broad spectrum of εHf(t) (mainly between − 5 and + 10) with TDMHf of 1800–2500 Ma. These data suggest that eclogitic metasediments are derived from a mixture of Proterozoic continent crust and juvenile early Paleozoic oceanic and/or island arc crust, and their protoliths likely were deposited in a terrigenous-dominated continental margin basin rather than a pelagic oceanic crust environment. The new results are consistent with subduction erosion of the active continental margin during south-dipping subduction, as these sediments, formed in a fore-arc environment close to the Qilian block to the south, were transported in the subduction zone to 60–70 km depth prior to their exhumation

Bio-Inspired Fabrication of Hierarchical FeOOH Nanostructure Array Films at the Air–Water Interface, Their Hydrophobicity and Application for Water Treatment

Hierarchical FeOOH nanostructure array films constructed by different nanosized building blocks can be synthesized at the air–water interface <i>via</i> a bio-inspired gas–liquid diffusion method. In this approach, poly(acrylic acid) (PAA) as a crystal growth modifier plays a crucial role in mediating the morphology and polymorph of FeOOH crystals. With the increase of PAA concentration, the shape of the building blocks assembling into FeOOH films can be tailored from nanosheets, to rice spikes, then to branched fibers, and finally to nanowires. What is more, a low concentration of PAA will induce the formation of α-FeOOH, while a high one could stabilize FeOOH in the form of the γ-FeOOH phase. After being modified with a thin layer of polydimethylsiloxane (PDMS), the as-prepared FeOOH films exhibited strong hydrophobicity with water contact angles (CA) from 134° to 148° or even superhydrophobicity with a CA of 164° in the sample constructed by nanosheets. When the FeOOH nanostructures were dispersed in water by ultrasound, they displayed quite promising adsorption performance of heavy metal ions for water treatment, where the highest adsorption capacity can reach 77.2 mg·g^–1 in the sample constructed by nanowires. This bio-inspired approach may open up the possibilities for the fabrication of other functional nanostructure thin films with unique properties

Graphene Sandwiched by Sulfur-Confined Mesoporous Carbon Nanosheets: A Kinetically Stable Cathode for Li–S Batteries

The practical use of lithium–sulfur batteries for the next-generation energy storage, especially the automobiles, was hindered by low electronic conductivity of sulfur and the resulting poor rate capabilities. Here, we report a sulfur–carbon composite by confining S into a graphene sandwiched in mesoporous carbon nanosheets with a two-dimensional ultrathin morphology, suitable mesopore size and large pore volume, and excellent electronic conductivity. Serving as cathode material for a Li–S battery, the elaborately designed S/C composite leads to “kinetically stable” transmissions of Li ions and electrons, triggering a stable electrochemistry and a record-breaking rate performance. In this way, the S/C composite has been proved a promising cathode material for high-rate Li–S batteries targeted at automobile storage

Gold Nanoparticle Functionalized Artificial Nacre: Facile <i>in Situ</i> Growth of Nanoparticles on Montmorillonite Nanosheets, Self-Assembly, and Their Multiple Properties

Artificial nacre based on clay nanosheets have been emerging as a new generation of bioinspired materials due to their super mechanical, fire-retardant, heat-shield, and gas barrier properties. Functional design in artificial nacre is highly demanded to further broaden the applications of these promising bioinspired materials. However, there is rarely a report on the functionalization of artificial nacre at present possibly due to the lack of a feasible strategy to introduce functional components in nacre-like materials without weakening other properties. In this study, we report a feasible method to fabricate artificial nacre-like functional hybrid films by using Au nanoparticle (NP) modified natural clay montmorillonite (MTM) nanosheets as efficient two-dimensional building blocks. First, Au NPs-chitosan-MTM hybrid nanosheets were prepared and homogeneously dispersed in deionized water by the facile <i>in situ</i> growth of Au NPs on chitosan-MTM nanosheets. Then, the obtained Au NPs-chitosan-MTM hybrid nanosheet suspension can be sprayed or vacuum filtrated to form nacre-like layered hybrid nanocoatings or free-standing hybrid films, respectively. Finally, as-fabricated artificial nacre nanocoatings or hybrid films have been demonstrated to behave with surface enhanced Raman scattering (SERS), catalytic, and photothermal conversion properties indicating the successful functionalization of artificial nacre by introducing Au NPs