Zhangxun Xia

Hybrid Polymer Nanoarrays with Bifunctional Conductance of Ions and Electrons and Enhanced Electrochemical Interfaces

Ion migration and electron transfer are crucial phenomena in electrochemistry and interfacial sciences, which require effective coupling and integration of separated charge pathways within medium materials. Here, in this work, we fabricated an ordered nanowire material based on hybrid polymers of polypyrrole, with electronic conductance, and perfluorosulfonic acid ionomers, with ionic conductance, via a facile one-step electrochemical route. Because of the nanoconfined effects for the different charge-transfer channels within the nanowire polymer matrix, the electronic and ionic conductivities of the hybrid polymer are surprisingly enhanced, being 26.4 and 0.096 S cm-1, respectively. Such an improvement in the formation of charge pathways also leads to an increased electrochemical capacitance through enlargement of the area of ion/electron transport boundaries, which may show great potential in the applications of supercapacitors, fuel cells, rechargeable batteries, and other electrochemical devices.

Hybrid polymer matrix composite containing polyaniline and Nafion as novel precursor of the enhanced catalyst for oxygen reduction reaction

A hybrid polymer matrix composite has been synthesized by in situ polymerization of aniline monomers into Nafion framework and characterized by X-ray diffraction and thermo-gravimetric analysis, which serves as a novel nitrogen precursor for metal–nitrogen-doped carbon catalyst. The electrostatic interaction between the amino groups of polyaniline and sulfonate groups of Nafion is found to be helpful for the promotion of thermal stability of the nitrogen precursor, which increases the nitrogen content of the catalyst. High specific surface area can be achieved via the decomposition and volatilization of Nafion in the pyrolysis procedure. The half-wave potential of the Nfn/PA/Fe-2 catalyst is 0.879 V, larger than that of the commercial Pt/C catalyst (E1/2 = 0.860 V). After 5000 cycles in alkaline media, the half-wave potential of Nfn/PA/Fe-2 decreases by 19 mV, which exhibits the excellent electrochemical durability and promising application in fields of metal–air batteries and alkaline fuel cells.

Graphitization induced by KOH etching for the fabrication of hierarchical porous graphitic carbon sheets for high performance supercapacitors

Porous graphitic carbons are promising candidates for energy conversion and storage. At present, it is highly desired but remains challenging to construct high-surface-area hierarchical porous graphitic carbons. Herein, graphitic carbon nanosheets with hierarchical pores are easily fabricated from a multifunctional carbonaceous precursor (pentaerythritol melamine phosphate or PMP). The PMP carbonaceous precursor can be readily converted into a 3D macroporous scaffold enclosed by carbon nanosheets via chemical foaming without any sacrificial templates and special drying procedures. Then a subsequent potassium hydroxide chemical activation process dramatically increases the surface area (up to 3853 m2 g−1) and porosity (up to 2.79 cm3 g−1). Simultaneously, graphitization of the carbon nanosheets was promoted with increased aromaticity and size of the polyaromatic units via breaking the phosphate ester bonds with KOH etching at a temperature as low as 800 °C. The resulting porous graphitic carbon nanosheets are constructed with an interconnected continuous three-dimensional network surrounded by predominantly multilayer sp2-bonded carbon with a dense nanometer scale pore structure. Due to such synergistic features, the resulting porous graphitic carbon nanosheets deliver 188 F g−1 specific capacitance and excellent rate performance in nonaqueous electrolytes.

Chemical Foaming Coupled Self-Etching: A Multiscale Processing Strategy for Ultrahigh-Surface-Area Carbon Aerogels

Due to the unique structure, carbon aerogels have always shown great potential for multifunctional applications. At present, it is highly desirable but remains challenging to tailor the microstructures with respect to porosity and specific surface area to further expand its significance. A facile chemical foaming coupled self-etching strategy is developed for multiscale processing of carbon aerogels. The strategy is directly realized via the pyrolysis of a multifunctional precursor (pentaerythritol melamine phosphate) without any special drying process and multiple steps. In the micrometer scale, the macroporous scaffold structures with interconnected and strutted carbon nanosheets are built up by chemical foaming from decomposition of melamine, whereas the meso/microporous nanosheets are formed via self-etching by phosphorus-containing species. The delicately hierarchical structures and record-breaking specific surface area of 2668.4 m2 g-1 render the obtained carbon aerogels great potentials for absorption (324.1-593.6 g g-1 of absorption capacities for varied organic solvents) and energy storage (338 F g-1 of specific capacitance). The construction of such novel carbon nanoarchitecture will also shed light on the design and synthesis of multifunctional materials.