Chaopeng Fu

Facile Preparation of High‐Quality Graphene Scrolls from Graphite Oxide by a Microexplosion Method

Figure 1 . a) Structure diagrams of GS, MWCNT, and GSS. b) Sketch showing the preparation steps of GSS based on a microexplosion method. Owing to their 1D structure and remarkable mechanical, physical, and electrical properties, carbon nanotubes (CNTs) have attracted considerable interest in various applications over the past decades. [ 1 ] In recent years, graphene sheets (GS), the ideal 2D sp 2 hybridized structure, are the basic building blocks for other carbon allotropes, such as 0D fullerenes, 1D CNTs, and 3D graphite (G). GS have been actively developed because of their superb characteristics, such as high chemical stability, excellent electrical conductivity, and large surface area. [ 2 ] However, monolayer GS tends to form irreversible agglomerates during the drying process, which severely restricts the development of further researches. [ 3 ]

Preparation of well-dispersed PdAu bimetallic nanoparticles on reduced graphene oxide sheets with excellent electrochemical activity for ethanol oxidation in alkaline media

Chemically reduced graphene oxide sheets-supported PdAu (PdAu/CRG) nanocomposites were prepared facilely by co-reduction of graphene oxide sheets, PdCl2 and HAuCl4. Then the PdAu/CRG nanocomposites were characterized by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results reveal that PdAu bimetallic nanoparticles with an average diameter of 6 nm are dispersed uniformly on the chemically reduced graphene oxide sheets (CRG). The electrocatalytic performance of the PdAu/CRG catalyst was studied by cyclic voltammetric and chronoamperometric measurements. Electrochemical experiments show that the PdAu/CRG catalyst has excellent catalytic activity and good stability for ethanol oxidation, indicating that the readily available CRG is an outstanding catalyst carrier for ethanol oxidation in alkaline media.

Co9S8 nanoparticles embedded in a N, S co-doped graphene-unzipped carbon nanotube composite as a high performance electrocatalyst for the hydrogen evolution reaction

In this work, we successfully fabricated a three-dimensional (3D) hierarchical ternary composite by embedding Co9S8 nanoparticles in a nitrogen and sulfur co-doped graphene-unzipped carbon nanotube matrix (Co9S8/NSG-UCNTs) through a facile and controllable one-step pyrolysis method using a graphite oxide/oxidized unzipped carbon nanotubes/cobalt nitrate/thiourea composite as the precursor. The as-prepared 3D ternary composite displays superior catalytic performance for the hydrogen evolution reaction (HER), which outperforms most binary or ternary carbon-based composites in the literature. The HER overpotentials are 65 mV and 86 mV when the current densities reach 10 mA cm−2 and 20 mA cm−2, respectively, and the exchange current density reaches 0.503 mA cm−2. Also, it demonstrates good stability reflected from the negligible activity decrease after 1000 consecutive cycles. The excellent electrocatalytic performance of the Co9S8/NSG-UCNT ternary composite is attributed to the co-effect of the abundant HER active sites induced by Co9S8 nanoparticles, structural defects existing in the carbon support caused by N and S co-doping and outstanding conductivity resulting from the 3D structure.

Facile Self‐Assembly Synthesis of PdPt Bimetallic Nanotubes with Good Performance for Ethanol Oxidation in an Alkaline Medium

PdPt bimetallic nanotubes were prepared by the self-assembly of Pt and Pd on Te nanowires at room temperature. The morphologies of the as-prepared PdPt nanotubes were investigated by scanning electron microscopy and transmission electron microscopy, and the results display a large amount of PdPt bimetallic nanotubes with a diameter of 10-20 nm and a length of several micrometers. The composition and structure of the nanotubes were characterized by X-ray diffraction, high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy spectrum analysis, and the results display uniform compositional distributions of both elements (Pd and Pt). The mechanism of the formation of the nanotube structure was supposed. The electrocatalytic performance of PdPt nanotubes were studied by cyclic voltammetry and chronoamperometry. Electrochemical results show that the as-prepared PdPt nanotube catalysts have not only high activity but also good stability for ethanol oxidation in alkaline medium.

Synthesis of curly graphene nanoribbon/polyaniline/MnO2 composite and its application in supercapacitor

Curly graphene nanoribbon/polyaniline/MnO2 (CGNR/PANI/MnO2) nanocomposites with a unique structure is prepared. The formation mechanism of the CGNR/PANI/MnO2 nanocomposite was proposed, and the morphology and structure were characterized by electron microscopy, X-ray diffraction, and Raman spectroscopy. The CGNR/PANI/MnO2 nanocomposite was investigated for supercapacitor applications. The CGNR/PANI/MnO2 electrode delivered a very high specific capacitance of 496 F g−1, which was much higher than that of CGNR (131 F g−1), PANI (301 F g−1) and MnO2 (33 F g−1), whereas 81.1% of its initial capacitance was retained after 5000 cycles at a scan rate of 50 mV s−1. The CGNR/PANI/MnO2 electrode was also evaluated via a two-electrode configuration, and the supercapacitor delivered a specific capacitance of 103 F g−1. The enhanced electrochemical performance of the CGNR/PANI/MnO2 electrode was ascribed to the unique structure and the synergetic effect of the three components in the composite.

Hydrothermal preparation of nitrogen, boron co-doped curved graphene nanoribbons with high dopant amounts for high-performance lithium sulfur battery cathodes

In this work, we for the first time synthesized nitrogen, boron co-doped curved graphene nanoribbons (NBCGNs) by a facile hydrothermal process using oxidized curved graphene nanoribbons (O-CGNs), urea and boric acid as the carbon precursor and heteroatom sources. The influence of N and B co-doping on the morphology, structure, composition and related electrochemical performance of the NBCGNs was systematically investigated, and the results show that urea and boric acid coexisting in the hydrothermal system not only act as the N and B doping sources but also act as the catalysts to boost the synergistical doping of N and B. It is the synergistical effect of N and B co-doping that endows the NBCGNs with enlarged specific surface area as well as pore volume, improved conductivity, promoted sulfur dispersibility and strengthened adsorbability for polysulfides caused by the notably increased doped N and B contents and higher percentage of the N–B structure when compared with the counterparts. As a result, the as-prepared NBCGN/S cathode presented synergistically enhanced cyclability and rate capability. Therefore, our results not only provide a superior carbon host for Li–S batteries but also offer a common approach to the preparation of heteroatom doped carbon nanomaterials with an optimized structure and composition.

A novel method to prepare a nanotubes@mesoporous carbon composite material based on waste biomass and its electrochemical performance

Hierarchical nanotubes@mesoporous carbon composite materials were controllably synthesized by an innovative method based on plant waste corncob and nitrogen source melamine via thermal treatment. The corncob provides both a carbon source and a small amount of Fe as the catalyst, while melamine offers a nitrogen source. Corncobs were firstly pretreated with concentrated sulfuric acid and then mixed with melamine. After calcination at 800 °C for 2 hours, a new composite carbon material with a unique structure with a large amount of thin walled nitrogen-doped carbon nanotubes orderly and vertically growing on the mesoporous carbon frame was obtained. The diameter of nanotubes is ∼50 nm while their length varies from 0.1–20 μm, which could be controlled by adjusting the ratio of pretreated corncob to melamine. Meanwhile, the composite material possesses stable interconnected pores and channels with a high surface area of 1100 m2 g−1, which significantly accelerated the transfer rates of ions and electrons. The electrochemical test results demonstrated that this composite material exhibits a superior capacitance of 538 F g−1 in an aqueous electrolyte and 320 F g−1 in an organic electrolyte at a current density of 1 A g−1. The specific capacitance of the composite material remained up to 90% of the initial value after 10 000 cycles, showing excellent long-term cycling stability. For lithium sulfur battery application, the composite material as a sulfur host delivered an initial capacity of 1047 mA h g−1, and exhibited a relatively stable cycling performance, maintained a capacity of 682 mA h g−1 for 300 charge/discharge cycles at 0.5C. The structure, morphology and growth mechanism of the composite material were also analyzed and discussed in detail.

Three-dimensional hierarchical porous nitrogen and sulfur co-doped graphene nanosheets for oxygen reduction in both alkaline and acidic media

Heteroatom‐doped carbon materials show superior oxygen reduction reaction (ORR) performance and served as alternatives to Pt‐based catalysts for the commercialization of fuel cells. However, these doped carbon materials only show good ORR activity in alkaline medium, they are generally less effective in acidic electrolytes. The appropriate combination of high dopant distribution and engineered morphology of doped carbon materials is essential to realize high ORR performance. Herein, we propose a novel and effective approach to synthesize three‐dimensional hierarchical porous nitrogen and sulfur‐codoped graphene nanosheets (NSG) as ORR catalysts in both alkaline and acid media. Firstly, the self‐assembled pyrrole layer was polymerized on graphene oxide template to form a molecule‐thick polypyrrole (PPy) layer using (NH4)2S2O8 oxidant, resulting in a sandwich‐like S‐containing PPy/GO nanosheets (S–PPy–GO–PPy–S), then the S–PPy–GO–PPy–S was pyrolyzed to generate 3 D hierarchical porous NSG with uniformly distributed high level multiple dopant (9.05 at % of N and 1.65 at % of S). As a result, the NSG exhibits comparable or even better ORR performance in both alkaline and acid media than the noble metal Pt/C catalyst. The achieved high performance is ascribed to the uniformly distributed high content doped elements and three‐dimensional hierarchical porous structure, providing more active sites for ORR.

In Situ Self-Template Synthesis of Fe–N-Doped Double-Shelled Hollow Carbon Microspheres for Oxygen Reduction Reaction

Herein, we reported a special Fe-N-doped double-shelled hollow carbon microsphere (Fe-N-DSC) which was prepared by a facile, in situ polymerization followed by pyrolysis. With porous ferroferric oxide (Fe3O4) hollow microspheres as the templates, where pyrrole monomers were dispersed around the outer surface and prefilled the interior space. By adding hydrochloric acid, Fe3+ ions were released to initiate polymerization of pyrrole on both the outer and inner surfaces of Fe3O4 microspheres until they were completely dissolved, resulting in the Fe-containing polypyrrole double-shelled hollow carbon microspheres (Fe-PPY-DSC). The Fe-PPY-DSC was then pyrolyzed to generate the Fe-N-DSC. The Fe3O4 hollow microspheres played trifunctional roles, i.e., the template to prepare a double-shelled hollow spherical structure, the initiator (i.e., Fe3+ ions) for the polymerization of pyrrole, and the Fe source for doping. The Fe-N-DSC exhibited a superior catalytic activity for oxygen reduction as comparable to commercial Pt/C catalysts in both alkaline and acidic media. The high catalytic performance was ascribed to the special porous double-shelled hollow spherical structure, which provided more active sites and was beneficial to a high-flux mass transportation.