7 research outputs found

    Formation of Asymmetric Bowl-Like Mesoporous Particles via Emulsion-Induced Interface Anisotropic Assembly

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    Mesoporous colloidal particles with tailored asymmetric morphologies and radially oriented large channels are of great importance for development of new carriers for nanoencapsulation, high-performance mass transport nanosystems, and complex assembly structures. However, controllable anisotropic growth to asymmetric mesoporous particles is very challenging via the universal surfactant-directed soft-templating method. Herein we report a simple emulsion-induced interface anisotropic assembly approach to synthesize bowl-like mesoporous polydopamine particles with diameter of ∼210 nm, well-controlled radially oriented mesochannels, and large pore size of ∼11 nm. This interface-driven approach also creates opportunities for tailoring the assembly and formation of various asymmetric and symmetric polydopamine particles. Bowl-like mesoporous carbon particles with radially oriented channels, high accessible surface area of 619 m<sup>2</sup> g<sup>–1</sup>, and large pore size of ∼8 nm can be fabricated by subsequent hydrothermal treatment and calcination under nitrogen atmosphere. Lastly, we demonstrate that the as-derived bowl-like mesoporous carbon particles manifest enhanced electrocatalytic performance for oxygen reduction reaction in alkaline electrolyte

    Metal–Organic-Frameworks-Derived General Formation of Hollow Structures with High Complexity

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    Increasing the complexity of hollow structures, in terms of chemical composition and shell architecture, is highly desirable for both fundamental studies and realization of various functionalities. Starting with metal–organic frameworks (MOFs), we demonstrate a general approach toward the large-scale and facile synthesis of complex hollow microboxes via manipulation of the template-engaged reactions between the Prussian blue (PB) template and different alkaline substances. The reaction between PB microcubes with NaOH solution leads to the formation of Fe­(OH)<sub>3</sub> microboxes with controllable multishelled structure. In addition, PB microcubes will react with the conjugate bases of metal oxide based weak acids, generating multicompositional microboxes (Fe<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>/GeO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub>, and Fe<sub>2</sub>O<sub>3</sub>/B<sub>2</sub>O<sub>3</sub>), which consist of uniformly dispersed oxides/hydroxides of iron and another designed element. Such complex hollow structures and atomically integrated multiple compositions might bring the usual physiochemical properties. As an example, we demonstrate that these complex hollow microboxes, especially the Fe<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub> composite microboxes, exhibit remarkable electrochemical performance as anode materials for lithium ion batteries

    Highly Efficient Removal of Organic Dyes from Waste Water Using Hierarchical NiO Spheres with High Surface Area

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    A facile solvothermal method has been developed for large-scale preparation of uniform spheres of a nickel–ethylene glycol complex (Ni-EG complex) with a hierarchical nanostructure. The dispersibility and hierarchical structure of the Ni-EG particles can be tuned by varying the concentration of additives added. On the basis of experimental observations, a plausible mechanism has been proposed to understand the formation process of the Ni-EG complex spheres. Calcining these as-prepared Ni-EG complex spheres at 300 °C in air results in uniform porous NiO spheres with a high specific surface area of 222 m<sup>2</sup> g<sup>–1</sup>. When served as the adsorbent for Congo red in water, the colloidal suspension of the as-prepared NiO hierarchical spheres exhibits a high adsorption capacity for the dye removal, suggesting their potential use in water treatment

    Designed Formation of Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> Double-Shelled Nanocages with Enhanced Pseudocapacitive and Electrocatalytic Properties

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    Hollow structures with high complexity in shell architecture and composition have attracted tremendous interest because of their great importance for both fundamental studies and practical applications. Herein we report the designed synthesis of novel box-in-box nanocages (NCs) with different shell compositions, namely, Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> double-shelled nanocages (DSNCs). Uniform zeolitic imidazolate framework-67/Ni–Co layered double hydroxides yolk-shelled structures are first synthesized and then transformed into Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs by thermal annealing in air. Importantly, this strategy can be easily extended to prepare other complex DSNCs. When evaluated as electrodes for pseudocapacitors, the Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs show a high specific capacitance of 972 F g<sup>–1</sup> at a current density of 5 A g<sup>–1</sup> and excellent stability with 92.5% capacitance retention after 12 000 cycles, superior to that of Co<sub>3</sub>O<sub>4</sub> NCs with simple configuration and Co<sub>3</sub>O<sub>4</sub>/Co<sub>3</sub>O<sub>4</sub> DSNCs. Besides, the Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs also exhibit much better electrocatalytic activity for the oxygen evolution reaction than Co<sub>3</sub>O<sub>4</sub> NCs. The greatly improved electrochemical performance of Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs demonstrates the importance of rational design and synthesis of hollow structures with higher complexity

    One-Pot Synthesis of Cubic PtCu<sub>3</sub> Nanocages with Enhanced Electrocatalytic Activity for the Methanol Oxidation Reaction

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    Noble metals such as platinum (Pt) are widely used as catalysts in fuel cells and other heterogeneous catalytic processes. However, there is an urgent need to develop substitutes for pure Pt catalysts to reduce the overall use of precious Pt and at the same time to enhance poisoning resistance. A promising strategy is to design Pt based bi- or trimetallic nanostructures because their unique structures and compositions would enhance their catalytic performance. In this study, we report the synthesis, characterization, and electrochemical evaluation of cubic intermetallic PtCu<sub>3</sub> nanocages. The influential effects of several important experimental parameters on the final products have been explored through systematic studies on the growth of PtCu<sub>3</sub> nanocages. Relative to the current commercial Pt electrocatalyst, these PtCu<sub>3</sub> nanocages possess a more accessible surface area and a unique hollow structure, which contribute to improved electrocatalytic activity in the methanol oxidation reaction

    Formation of Fe<sub>2</sub>O<sub>3</sub> Microboxes with Hierarchical Shell Structures from Metal–Organic Frameworks and Their Lithium Storage Properties

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    Fe<sub>2</sub>O<sub>3</sub> microboxes with hierarchically structured shells have been synthesized simply by annealing Prussian blue (PB) microcubes. By utilizing simultaneous oxidative decomposition of PB microcubes and crystal growth of iron oxide shells, we have demonstrated a scalable synthesis of anisotropic hollow structures with various shell architectures. When evaluated as an anode material for lithium ion batteries, the Fe<sub>2</sub>O<sub>3</sub> microboxes with a well-defined hollow structure and hierarchical shell manifested high specific capacity (∼950 mA h g<sup>–1</sup> at 200 mA g<sup>–1</sup>) and excellent cycling performance

    Ultrathin and Ultralong Single-Crystal Platinum Nanowire Assemblies with Highly Stable Electrocatalytic Activity

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    Ultrathin one-dimensional (1D) nanostructures such as nanowires and nanorods have drawn considerable attention due to their promising applications in various fields. Despite the numerous reports on 1D nanostructures of noble metals, one-pot solution synthesis of Pt 1D nanostructures still remains a great challenge, probably because of the intrinsic isotropic crystal growth behavior of Pt. Herein, we demonstrate the facile solvothermal synthesis of nanowire assemblies composed of ultrathin (ca. 3 nm) and ultralong (up to 10 μm) Pt nanowires without involving any template. The oriented attachment mechanism is found to be partially responsible for the formation of such ultrathin Pt nanowires. The amine molecules generated during the reaction might assist the formation of nanowire assemblies. Importantly, the present system can be extended to synthesize Pt-based alloy nanowire assemblies such as Pt–Au and Pt–Pd. These Pt nanowires can be easily cast into a free-standing membrane, which exhibits excellent electrocatalytic activity and very high stability for formic acid and methanol oxidation and the oxygen reduction reaction
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