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Two kinds of phosphorus-modified onion-like carbons dominated by C-O-P bonds and C-P bonds were fabricated and further used as catalysts in the oxygen reduction reaction (ORR). The results show that the bonding state of phosphorus has a significant effect on the ORR catalytic activity. The formation of C-O-P bonds improves ORR activity, whereas C-P bonds play an adverse role in stabilizing the key intermediates during the ORR owing to the distorted graphitic structure, as confirmed by the work function value., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A promising energy storage material, MnO2 /hierarchically porous carbon (HPC) nanocomposites, with exceptional electrochemical performance and ultrahigh energy density was developed for asymmetric supercapacitor applications. The microstructures of MnO2 /HPC nanocomposites were characterized by transmission electron microscopy, scanning transmission electron microscopy, and electron dispersive X-ray elemental mapping analysis. The 3-5 nm MnO2 nanocrystals at mass loadings of 7.3-10.8 wt % are homogeneously distributed onto the HPCs, and the utilization efficiency of MnO2 on specific capacitance can be enhanced to 94-96 %. By combining the ultrahigh utilization efficiency of MnO2 and the conductive and ion-transport advantages of HPCs, MnO2 /HPC electrodes can achieve higher specific capacitance values (196 F g(-1) ) than those of pure carbon electrodes (60.8 F g(-1) ), and maintain their superior rate capability in neutral electrolyte solutions. The asymmetric supercapacitor consisting of a MnO2 /HPC cathode and a HPC anode shows an excellent performance with energy and power densities of 15.3 Wh kg(-1) and 19.8 kW kg(-1) , respectively, at a cell voltage of 2 V. Results obtained herein demonstrate the excellence of MnO2 /HPC nanocomposites as energy storage material and open an avenue to fabricate the next generation supercapacitors with both high power and energy densities., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Same selectivity hides different pathways: The same apparent 4-electron process for the oxygen-reduction-reaction hides different pathways over carbon-supported cobalt oxide catalysts depending on the potential. At low overpotentials, the ORR intermediate HO(2) (-) preferably disproportionates to oxygen, whereas at high overpotentials the disproportionation and reduction reaction occur in parallel., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Porous carbons with concurrently high specific surface area and electronic conductivity are desirable by virtue of their desirable electron and ion transport ability, but conventional preparing methods suffer from either low yield or inferior quality carbons. Here we developed a lithiothermal approach to bottom–up synthesize highly meso–microporous graphitized carbon (MGC). The preparation can be finished in a few milliseconds by the self-propagating reaction between polytetrafluoroethylene powder and molten lithium (Li) metal, during which instant ultra-high temperature (>3000 K) was produced. This instantaneous carbon vaporization and condensation at ultra-high temperatures and in ultra-short duration enable the MGC to show a highly graphitized and continuously cross-coupled open pore structure. MGC displays superior electrochemical capacitor performance of exceptional power capability and ultralong-term cyclability. The processes used to make this carbon are readily scalable to industrial levels. Porous carbons with high specific surface area and electronic conductivity are of interest for their electron and ion transport ability. Here authors use ultra-high temperature reactions of Li metal and polytetrafluoroethylene to make graphitized porous carbon for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

The recent mechanistic understanding of active sites, adsorbed intermediate products, and rate‐determining steps (RDS) of nitrogen (N)‐modified carbon catalysts in electrocatalytic oxygen reduction (ORR) and oxygen evolution reaction (OER) are still rife with controversy because of the inevitable coexistence of diverse N configurations and the technical limitations for the observation of formed intermediates. Herein, seven kinds of aromatic molecules with designated single N species are used as model structures to investigate the explicit role of each common N group in both ORR and OER. Specifically, dynamic evolution of active sites and key adsorbed intermediate products including O2 (ads), superoxide anion O2−*, and OOH* are monitored with in situ spectroscopy. We propose that the formation of *OOH species from O2−* (O2−*+H2O→OOH*+OH−) is a possible RDS during the ORR process, whereas the generation of O2 from OOH* species is the most likely RDS during the OER process. [ABSTRACT FROM AUTHOR]

Abstract The applications of nanocarbon materials have been drawing an ever-increasing attention due to their unique physical and chemical properties. The performance of nanocarbon materials is determined or significantly influenced by their surface chemical composition and structure, including edges, holes, heteroatoms and functional groups etc. As a result, the accurate characterization and interpretation of the surface chemical properties of nanocarbon is extremely important, and numerous mature techniques were developed with the rapid progress of nanotechnology and characteristic instrumentation. In this review we summarized the latest development of characterization techniques for nanocarbon materials, the principles behind the techniques and the related data analysis methods. The characterization techniques are divided into four categories, including spectroscopy (IR, Raman, XPS, UPS, XAS, NMR and EELS), surface reaction (Boehm titration, potentiometric titration, chemical titration and TPSR), electron/probe microscopy (TEM, SEM, STM and AFM) and electro-chemistry methods. The most suitable application circumstances, test conditions and chemical information derivable by each characterization method are pointed out with examples, and the advantages and shortcomings of each technique are thoroughly discussed. We express the idea that full-scale structural information of nanocarbon could only be obtained by proper and comprehensive application of multiple kinds of characterization methods. [ABSTRACT FROM AUTHOR]

Dual-ion batteries are promising devices, owing to their compatibility of high energy density and high power density, provide that the volume expansion of positive graphite and the decomposition of the electrolyte are well addressed. Herein, we report a facile strategy of using low-cost carbon fiber paper for package enhancement of dual-ion batteries. The three-dimensional structure offers both conductivity and structure integrity, while the highly graphitic fiber paper endows the high intercalation potential towards high energy density. High stability results from such integrative electrode structure. Matching with electrical double-layer capacitive graphene and ionic liquids, with a wide electrochemical stability window, a dual-ion battery has been fabricated to achieve a specific energy of 149 Wh/kg at a specific power of 1011 W/kg, and the specific energy retains 85 % after 1000 cycles. This accessible 3D paper electrode provides a new route for an integral electrode construct that can be used in ultrastable, high-efficiency energy-storage devices. [ABSTRACT FROM AUTHOR]

In alkaline medium, it seems that both metal-free and iron-containing carbon-based catalysts, such as nitrogen-doped nanocarbon materials, FeO x-doped carbon, and Fe/N/C catalysts, are active for the oxygen reduction reaction (ORR). However, the order of activity of these different active compositions has not been clearly determined. Herein, we synthesized nitrogen-doped carbon black (NCB), Fe3O4/CB, Fe3O4/NCB, and FeN4/CB. Through the systematic study of the ORR catalytic activity of these four catalysts in alkaline solution, we confirmed the difference in the catalytic activity and catalytic mechanism for nitrogen, iron oxides, and Fe-N complexes, respectively. In metal-free NCB, nitrogen can improve the ORR catalytic activity with a four-electron pathway. Fe3O4/CB catalyst did not exhibit improved activity over that of NCB owing to the poor conductivity and spinel structure of Fe3O4. However, FeN4 coordination compounds as the active sites showed excellent ORR catalytic activity. [ABSTRACT FROM AUTHOR]

The lithium-oxygen (Li-O2) battery is a very appealing candidate for advanced high energy applications owing to its exceptionally high specific energy. However, its poor energy efficiency, rate capability, and cyclability remain key barriers to its practical application. In this work, using a rationally designed cathode based on a bimodal mesoporous nitrogen-doped graphene/carbon nanotube (NGC) composite, we have developed a Li-O2 battery demonstrating enhanced round-trip efficiency (ca. 85 %) and excellent cyclability over 400 cycles under a high current rate of 500 mA g−1. The excellent cyclability and rate capability are attributed to improved stability of the aggressive LiO2 intermediate on the nitrogen-doped carbon surface in addition to the favorable hierarchical architecture of NGC. These results demonstrate a valuable research direction to achieve highly stable and reversible Li-O2 batteries through tuning the surface chemistry of the cathode in addition to finding a stable electrolyte solvent. [ABSTRACT FROM AUTHOR]

Carbon is a unique and versatile element in nature that can form different architectures. Heteroatom (e.g., B, N, O, P, and S) modification has been proven to be an effective way to tailor the chemical and electrical properties of the carbon surface. Moreover, nanocarbons have been reported to be good supports for metal nanoparticles (NPs). It is essential to study the metal-support interaction between surface-modified carbon and metal NPs to understand performance. Advanced analytical transmission electron microscopy techniques are powerful tools that can be used to probe the metal-carbon support interaction in carbon-supported metal catalysts, as they can directly uncover local structures of the surface and the bulk of catalysts at the atomic scale and can also reveal chemical and electronic structural information that is related to their synthesis and catalytic properties significantly affecting their performance. Herein, several selected examples will be reviewed. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a decisive role for the efficiency of fuel cells and metal-air batteries. The nitrogen doped carbon materials with low cost and long durability are potential catalysts to replace precious metal catalyst for oxygen electrochemistry; however, the unexposed active sites induced by the bulk dopant atoms are hardly accessible and consequently scarcely contribute to the catalytic property. In this study, carbon nanotubes (CNTs) are selected as the platform to demonstrate the potential of full exposure of 'active sites' at the surface. Novel N-doped carbon coaxial nanocables with the pristine CNTs as the core and the N-doped carbon layers as the shell are proposed. The accessible and efficient utilization of the integrated nitrogen atoms enriched on the surface, together with the undestroyed intact inner walls, render the electrocatalyst much enhanced electrocatalytic activity and high electrical conductivity of 3.3 S cm−1, therefore, N-doped nanocables afford higher oxygen reduction current, ∼51 mV positively shift onset potential, low peroxide generation, as well as lower overpotential and higher current for oxygen evoluation reaction. [ABSTRACT FROM AUTHOR]

Different sp2@sp3 core-shell structures are obtained on nanodiamond by using annealing treatment at increasingly higher temperatures. The resulting nanocarbons can serve as model catalysts to investigate the structural effect on the evolution and chemical nature of oxygen functional groups for oxidative dehydrogenation reactions. We studied in situ reactions and characterization data and found that the initial existence of oxygen-containing groups on a catalyst surface had a low contribution to the catalytic performance. The active oxygen species can be generated promptly in situ by the chemisorption of O2 under the reaction conditions and involved in catalytic dehydrogenation process following a redox mechanism. For different hybridized nanostructures, the same types of generated active oxygen groups show different catalytic capabilities, which can be regulated by the sp2-hybridized carbon fraction of nanodiamond. The ketonic carbonyl groups formed on graphitic onion-like carbon surface are more active and can improve the selectivity to alkenes significantly compared with the initial nanodiamond and traditional carbon nanotubes. [ABSTRACT FROM AUTHOR]

Hybrid nanocarbon, comprised of a diamond core and a graphitic shell with a variable sp2-/sp3-carbon ratio, is controllably obtained through sequential annealing treatment (550-1300 °C) of nanodiamond. The formation of sp2 carbon increases with annealing temperature and the nanodiamond surface is reconstructed from amorphous into a well-ordered, onion-like carbon structure via an intermediate composite structure-a diamond core covered by a defective, curved graphene outer shell. Direct dehydrogenation of propane shows that the sp2-/sp3-nanocomposite exhibits superior catalytic performance to that of individual nanodiamond and graphitic nanocarbon. The optimum catalytic activity of the diamond/graphene composite depends on the maximum structural defectiveness and high chemical reactivity of the ketone groups. Ketone-type functional groups anchored on the defects/vacancies are active for propene formation; nevertheless, once the oxygen functional groups are desorbed, the defects/vacancies alone might be active sites responsible for the CH bond activation of propane. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are selected as the platform to demonstrate the potential of full exposure of “active sites” at the surface by Q. Zhang, D. S. Su, F. Wei, and co‐workers on page 5956. Novel nitrogen‐doped carbon coaxial nanocables with the pristine CNTs as the core and the N‐doped carbon layers as the shell are available. They possess very high electrical conductivity and much enhanced electrocatalytic activity for both oxygen reduction and evolution reaction. [ABSTRACT FROM AUTHOR]

Two-dimensional carbon nanomaterials have been widely applied in the field of catalysis due to their unique structure and properties. In this work, the cobalt and nitrogen co-doped two-dimensional carbon nanomaterials with graphene-like and porous structure were synthesized via template method. Here, rhodamine B acted as the carbon source was intercalated into the CTAB-pillared montmorillonite. And the cobalt porphyrin was used as the cobalt and nitrogen precursors that made a great contribution to generate highly dispersed active sites due to their unique Co N 4 structure. The characterization techniques such as HAADF-STEM, XPS, XRD, and Nitrogen adsorption-desorption were used to investigate the surface composites and structures of the Co N C catalysts. In addition, the as-prepared catalysts with relatively high specific surface area, large pore volume, and well-dispersed active sites were further evaluated for the selective oxidation of ethylbenzene using tert -butyl hydroperoxide as oxidant. The Co N/C s H catalyst synthesized via impregnation method presented an ethylbenzene conversion of 96% and selectivity of 99% to acetophenone, which was the highest catalytic activity among the investigated catalysts. The superior catalytic performance could be ascribed to the unique two-dimensional porous graphene-like structure, highly dispersed active sites, and the synergistic effect between the Co O x and Co N x . [ABSTRACT FROM AUTHOR]

With graphene oxide (GO) as ‘shape-directing’ agent, carbon aerogels with tunable hierarchical porous structure were prepared by one-step carbonization method. It was found that the content of GO had a significant effect on their pore structures. When GO loading was up to 1.43 wt‱, it possessed an ultrahigh specific surface area (SSA) of 2728 m 2 g −1 , large pore volume of 1.82 cm 3 g −1 and excellent mechanical properties. Benefiting from the high SSA and unique hierarchical porous microstructure, possible future applications of the as-obtained carbon aerogels could be in the fields of energy storage, electrochemistry, and adsorption. [ABSTRACT FROM AUTHOR]

Due to highly heterogeneity of pyrolyzed transition metal-nitrogen-carbon (M-N-C) catalyst, elucidating mechanisms of roles of metal in enhancing oxygen reduction reaction (ORR) is challenging. Here, we design a surface structurally-defined precursor with Fe-N coordination to atomically disperse iron (Fe) on N-doped carbon hollow microspheres surface (NHMs@Fe) by pyrolysis of the precursor. The obtained NHMs@Fe catalyst exhibits a high ORR activity comparable to commercial Pt/C catalyst. The detailed analyses confirmed that (i) Fe atoms are uniformly distributed on N-poor carbon surface, and (ii) the designed Fe-N x coordination are destroyed and don't convert into Fe-N x active sites after thermal activation. We find that single Fe atoms produced by carbothermal reduction are directly trapped into adjacent carbon vacancies generated by the removal of N to create active sites for ORR. This work not only reveals the origin of activity of Fe-N-C catalyst but also opens an avenue for preparation of high-performance M-N-C catalysts. [Display omitted] • Fe atoms are uniformly dispersed on the N-doped carbon by pyrolysis of structure defined precursor. • The obtained NHMs@Fe catalyst exhibits a high ORR activity comparable to commercial Pt/C catalyst. • The designed Fe-N x coordination are destroyed and don't convert into Fe-N x sites after pyrolysis. • Single Fe atom is directly trapped into adjacent N-removed vacancy to create active site for ORR. • Low coordination single Fe atoms anchored on carbon vacancies are responsible for high ORR activity. [ABSTRACT FROM AUTHOR]