Research Article Issue
In situ fastening graphene sheets into a polyurethane sponge for the highly efficient continuous cleanup of oil spills
Nano Research 2017, 10 (5): 1756-1766
Published: 10 March 2017

Oil sorbents are an attractive option for oil-spill cleanup as they may be used for collection and complete removal of oil without adversely affecting the environment. However, traditional oil sorbents exhibit low oil/water separation efficiency and/or low oil-sorption capacity. In this study, an ultra-high performance graphene/polyurethane (PU) sponge has been successfully obtained by in situ polymerization in the presence of graphene dispersed in N-methylpyrrolidone (NMP). During polymerization, the NMP/graphene dispersion not only serves as a weak amine catalyst for the formation of the sponge, but promotes fixation of the graphene sheets in the framework of the PU sponge owing to the strong dipole interaction between NMP and graphene. The as-prepared graphene/PU sponge was used as an absorbing material for the continuous removal of oil from oil-spill water. The graphene/PU sponge can continuously and rapidly remove oils from immiscible oil/water mixtures in corrosive solutions, including strong acids and bases, hot water, and ice water, with an excellent separation efficiency of above 99.99%. In addition, the as-prepared graphene/PU sponge was effective in separating surfactant-stabilized emulsions with a high separation efficiency of > 99.91%.

Research Article Issue
Natural tea-leaf-derived, ternary-doped 3D porous carbon as a high-performance electrocatalyst for the oxygen reduction reaction
Nano Research 2016, 9 (5): 1244-1255
Published: 29 September 2016

To commercialize fuel cells and metal-air batteries, cost-effective, highly active catalysts for the oxygen reduction reaction (ORR) must be developed. Herein, we describe the development of low-cost, heteroatom (N, P, Fe) ternary-doped, porous carbons (HDPC). These materials are prepared by one-step pyrolysis of natural tea leaves treated with an iron salt, without any chemical and physical activation. The natural structure of the tea leaves provide a 3D hierarchical porous structure after carbonization. Moreover, heteroatom containing organic compounds in tea leaves act as precursors to functionalize the resultant carbon frameworks. In addition, we found that the polyphenols present in tea leaves act as ligands, reacting with Fe ions to form coordination compounds; these complexes acted as the precursors for Fe and N active sites. After pyrolysis, the as-prepared HDPC electrocatalysts, especially HDPC-800 (pyrolyzed at 800 ℃), had more positive onsets, half-wave potentials, and higher catalytic activities for the ORR, which proceeds via a direct four-electron reaction pathway in alkaline media, similar to commercial Pt/C catalysts. Furthermore, HDPC-X also showed enhanced durability and better tolerance to methanol crossover and CO poisoning effects in comparison to commercial Pt/C, making them promising alternatives for state-of-the-art ORR electrocatalysts for electrochemical energy conversion. The method used here provides valuable guidelines for the design of high-performance ORR electrocatalysts from natural sources at the industrial scale.

Research Article Issue
Self-healing superhydrophobic polyvinylidene fluoride/Fe3O4@polypyrrole fiber with core–sheath structures for superior microwave absorption
Nano Research 2016, 9 (7): 2034-2045
Published: 06 May 2016

Self-healing superhydrophobic polyvinylidene fluoride/Fe3O4@polypyrrole (F-PVDF/Fe3O4@PPyx ) fibers with core–sheath structure were successfully fabricated by electrospinning of a PVDF/Fe3O4 mixture and in situ chemical oxidative polymerization of pyrrole, followed by chemical vapor deposition with fluoroalkyl silane. The F-PVDF/Fe3O4@PPy0.075 fiber film produces a superhydrophobic surface with self-healing behavior, which can repetitively and automatically restore superhydrophobicity when the surface is chemically damaged. Moreover, the maximum reflection loss (RL) of the F-PVDF/Fe3O4@PPy0.075 fiber film reaches -21.5 dB at 16.8 GHz and the RL below -10 dB is in the frequency range of 10.6–16.5 GHz with a thickness of 2.5 mm. The microwave absorption performance is attributed to the synergetic effect between dielectric loss and magnetic loss originating from PPy, PVDF and Fe3O4. As a consequence, preparing such F-PVDF/Fe3O4@PPyx fibers in this manner provides a simple and effective route to develop multi-functional microwave absorbing materials for practical applications.

Research Article Issue
A bio-inspired Co3O4-polypyrrole-graphene complex as an efficient oxygen reduction catalyst in one-step ball milling
Nano Research 2015, 8 (11): 3461-3471
Published: 03 September 2015

The development of non-precious metal-based electrocatalysts has attracted much research attention because of their high oxygen reduction reaction (ORR) activities, low cost, and good durability. By one-step in-situ ball milling of graphite, pyrrole, and cobalt salt without resorting to high-temperature annealing, we developed a general and facile strategy to synthesize bio-inspired cobalt oxide and polypyrrole coupled with a graphene nanosheet (Co3O4-PPy/GN) complex. Herein, the exfoliation of graphite and polymerization of pyrrole occurred simultaneously during the ball milling process. Meanwhile, the Co3O4 and Co-Nx ORR active sites were generated from the oxidized cobalt ion, cobalt-PPy, and the newly exfoliated graphene nanosheets via strong π–π stacking interactions. The resultant Co3O4-PPy/GN catalysts showed efficient electrocatalytic performances for ORRs in an alkaline medium with a positive onset and reduction potentials of -0.102 and -0.196 V (vs. Ag/AgCl), as well as a high diffusion-limited current density (4.471 mA·cm-2), which was comparable to that of a Pt/C catalyst (4.941 mA·cm-2). Compared to Pt/C, Co3O4-PPy/GN catalysts displayed better long-term stability, methanol tolerance, and anti-CO-poisoning effects, which are of great significance for the design and development of advanced non-precious metal electrocatalysts.

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