Nitrogen-doped Carbon Network Research Articles

Hierarchical nanoarchitecture of vanadium disulfide decorated 3D porous carbon skeleton with improved electrochemical performance toward Li ion battery and supercapacitor

Vanadium disulfide (VS2) is deemed to be a competitive active material in electrochemical energy storage field in both lithium-ion battery and supercapacitor owing to its unique chemical and physical property. Nevertheless, serious aggregation and structure damage in continuous charge-discharges would result in a decreased capacity, an inferior cycling stability and a poor rate capability, which severly limits the practical application of VS2. In this current work, a hierarchical porous nanostructured composite composed of VS2 nanoparticles confined in gelatin-derived nitrogen-doped carbon network (VS2-NC) was successfully designed and synthesized via a simple freeze drying plus an annealing method. In this VS2-NC composite, porous architecture is conductive to providing high active surface areas, facilitating the access of electrolyte into active materials and ion diffusion. The confinement of carbon matrix on VS2 nanoparticles is beneficial to inhibition of the volume change, reinforcement of the structural stability and improvement of the overall electrical conductivity of composite. Benefitting from the advantages mentioned above, the as-prepared VS2-NC electrode demonstrates outstanding electrochemical performances. Employed as an anode for lithium ion battery, VS2-NC delivers a relatively high reversible capacity about ∼1061 mA h g−1 in 200-cycle test at 100 mA g−1. When applied in supercapacitor, VS2-NC electrode manifests a large pseudocapacitance of 407.3 F g−1 at a current density of 10 A g−1 and superior cycling stability.

Encapsulation of MXene/polydopamine in nitrogen-doped 3D carbon networks with high photothermal conversion efficiency for seawater desalination

With the rapid consumption of traditional fossil energy, the utilization of solar energy via photothermal conversion to obtain fresh water from seawater or wastewater should be a promising alternative to solve the shortage of energy resources. At present, evaporators based on diverse photothermal conversion materials have been developed, but most of them are still facing the drawbacks of complicated structure, complex preparation and poor salt resistance, which severely affect their broad practical applications. Multilayer-MXene (mMXene) and polydopamine (PDA) nanoparticles are two kinds of materials with excellent photothermal conversion efficiency. In this study, we loaded these two materials with optimized mass ratio into the thermally insulated and low-cost melamine foam, followed by simple annealing treatment to afford three-dimensional and self-floating carbonized MXene/PDA foam (CMPF) evaporators with high hydrophilicity, unpleasant thermal conductivity, and remarkable light absorbance. The evaporation rate of CMPF, as a result, could attain 1.598 kg m−2 h−1 under 1 sun (1 kW m−2) irradiation while the photothermal conversion efficiency is calculated to be 89.8%. In addition, CMPF-2 displays excellent desalination ability, self-desalination ability, good cycle stability and reliable safety performance as revealed by bacterial culture experiment. Combining these advantages, it has been revealed that CMPF-2 possesses certain feasible practical applications in seawater desalination.

A Bifunctional Nitrogen Doped Carbon Network as the Interlayer for Dendrite-Free Zn Anode

A Bifunctional Nitrogen Doped Carbon Network as the Interlayer for Dendrite-Free Zn Anode

Tungsten disulfide nanoparticles embedded in gelatin-derived honeycomb-like nitrogen-doped carbon networks with reinforced electrochemical pseudocapacitance performance

In this paper, we demonstrated a hierarchical honeycomb-like tungsten disulfide (WS2) composite nanostructure comprised of WS2 nanoparticles dispersed and embedded in gelatin-derived carbon networks with well-developed porous structures and high surface areas. In this composite, open porous architecture was favorable to easy access of electrolyte, efficient ion diffusion and relief of mechanical stress from volume variation. The unique inlaid configuration of WS2 nanoparticles in carbon matrix greatly inhibited aggregation of particles, improved structural stability and increased electrical conductivity. Profiting from these structural advantages, the optimized WS2 composite electrode demonstrated tremendously enhanced electrochemical properties. As an electrode material for pseudocapacitor, it exhibited a high capacitive value of 1305.5 Fg−1 under a current density of 0.2 A g−1. Even measured at 10 A g−1, the optimized WS2 composite still kept a high capacity of 482.6 Fg−1 and demonstrated a stable cycling performance during a long-period test. Moreover, an asymmetric capacitor based on assembly of WS2 composite cathode and activated carbon anode was fabricated. As tested under a current density of 0.1 A g−1, it could deliver a high capacitance of ∼135.9 Fg−1 and achieved an energy density of 27.2 Wh kg−1 along with a power density of 59.9 W kg−1.

Three-dimensional nitrogen-doped dual carbon network anode enabling high-performance sodium-ion hybrid capacitors

It is urgent for sodium-ion hybrid capacitors (SIHCs) to exploit a porous carbon anode that integrates high reversible specific capacity, rapid kinetics and superb cyclability. Herein, a three-dimensional dumpling-like glyururil-derived porous carbon@RGO composite (GLCG) constructed from nitrogen-doped (10.29 at.%) hierarchical porous carbon filling and highly conductive flexible RGO wrapper is synthesized. As for the Na half-cell, GLCG anode delivers high reversible specific capacity (282 mAhg-1 at 0.05 Ag−1) as well as superb rate capability (122.8 mAhg-1 at 10 Ag−1) and lifespan (3000 cycles at 2 Ag−1). Moreover, the origin of the excellent sodium-ion storage properties of GLCG is revealed by in-depth mechanism analysis. Consequently, a SIHCs with GLCG anode is constructed, which displays high energy density of 108 Wh kg−1, high power density of 14.2 kW kg−1 and long lifespan of 66% capacity retention after 5000 cycles at 2 Ag−1. This work provides an alternative avenue for the exploitation of high-performance carbon-based SIHCs anode.

Nitrogen-Doped Carbon Networks with Consecutive Conductive Pathways from a Facile Competitive Carbonization-Etching Strategy for High-Performance Energy Storage.

Recently, new carbonization strategies for synthesizing structure-controlled and high-performance carbon electrode materials have attracted great attentions in the field of energy storage and conversion. Here a competitive carbonization-etching strategy to prepare nitrogen-doped carbon polyhedron@carbon nanosheet (NCP@CNS) hybrids derived from zeolitic imidazolate framework-8 is presented. Consecutive conductive networks are constructed in the NCP@CNS hybrids during a unique carbonization-etching pyrolysis, where a competition between the formation of NCPs and CNSs exists. When the NCP@CNS hybrids are employed as supercapacitor electrodes, their hierarchically porous NCPs serve as ion-buffering reservoirs for offering fast ion transport channels, and the CNSs within hybrids not only link the NCPs together to build electron transfer pathways but also restrict the volume fluctuation of electrodes during charging and discharging process. As a result, the as-fabricated NCP@CNS electrode displays excellent electrochemical performances including a superior specific capacitance of 320 F g-1 , a high energy density of 22.2 W h kg-1 (5.6 W h kg-1 for symmetric device), and a long cycle life with capacitance retention of ≈101.8% after 5000 cycles. This study opens an encouraging avenue toward the tailored synthesis of metal-organic frameworks (MOFs)-derived carbon electrodes for renewable energy storage applications and devices.

Three-dimensional hollow nitrogen-doped carbon shells enclosed monodisperse CoP nanoparticles for long cycle-life sodium storage

Transition metal phosphides are emerging as promising anode materials of sodium ion batteries (SIBs) due to their high performance in terms of capacity and operational stability. Highly isolated CoP nanoparticles encapsulated in 3D hollow nitrogen-doped carbon networks (CoP/HNC composite) are designed via polymerization of poly-dopamine (PDA) on ZIF-67 and the subsequent in-situ phosphorization. Ultrafine CoP nanoparticles (10 ± 2 nm) are decorated in nitrogen-doped carbon polyhedral shells in a porous 3D hollow architecture. Benefiting from the unique construction, the CoP/HNC electrode delivers a high reversible long cycle-life capacity of 223 mA h g−1 for sodium storage at 500 mA g−1 after 700 cycles. DFT simulations indicate that Na atoms strongly bound to CoP surfaces, and significantly concentrate near CoP surfaces, beneficial for the Na ions storage in this composite material. These results suggest the CoP/HNC composite can be a promising anode material for SIBs. Besides, the designed strategy of CoP/HNC composite could be applied to fabricate other metal phosphides for electrochemical storage devices.

In-situ synthesis of ultrafine Co nanoparticles confined in interconnected nitrogen-doped carbon networks for enhanced reduction of 4-nitrophenol

The integration of 3d transition metal nanoparticles with carbon materials holds great promise to rationally design and fabricate advanced catalysts. In this work, a 3D hybrid of ultrafine Co nanoparticles strongly confined in interconnected nitrogen-doped carbon networks (Co@INC) was synthesized by one-step pyrolysis of polypyrrole/zeolitic imidazole framework composites (PPy/ZIF-67), and then was evaluated as catalysts toward the reduction of 4-nitrophenol (4-NP). Both pyrolyzed Co2+-coordinated PPy and ZIF-67 contributed to generate a large amount of highly-dispersed Co nanoparticles, which ensured structural integrity and high content of N doping. Benefitting from the 3D interconnected carbon networks for large mass transfer and considerably exposed active sites, the Co@INC possessed remarkedly enhanced catalytic performance with almost 100% of 4-NP conversion within 120 s by adding 0.06 mg of catalyst. Meanwhile, it also held outstanding stability and reusability. These findings provide new insight into fabricating the 3D transition metal–carbon hybrids derived from MOFs-related materials for catalytic application.

Implanting Cobalt Atom Clusters within Nitrogen-Doped Carbon Network as Highly Stable Cathode for Lithium-Sulfur Batteries.

Realization of highly efficient sulfur electrochemistry, as well as the high capacity of lithium-sulfur (Li-S) batteries, can be achieved by the scientific construction of electrode host materials. In this study, using molten NaCl, a 3D porous nitrogen-doped carbon with uniformly embedded Co atom clusters (Co/PNC) is developed by pyrolyzing the precursors with NaCl at high temperatures. In the composite structure, a network carbon skeleton containing hierarchical pores acts as an advanced matrix for sulfur electrodes, and the doping of N and Co is subject to inhibit the shuttle of long-chain lithium polysulfides through chemical adsorption. The Co/PNC, with the optimized amount of Co, delivers an initial specific capacity of 1105.4 mAh g-1 at 0.2 C with a capacity drop of only 0.064% after the cell is charged and discharged for 300 cycles at 1 C, revealing its potential in promoting the large-scale application of Li-S batteries.

Tunable Hollow Nanoreactors for In Situ Synthesis of GeP Electrodes towards High-Performance Sodium Ion Batteries.

The practical application of germanium phosphide (GeP) in battery systems is seriously impeded referring to the sluggish reaction kinetics and severe volume change. Nanostructure design that elaborately resolves the above issues is highly desired but still remains a big challenge. Herein, unique hollow nanoreactors assembled with nitrogen-doped carbon networks for in situ synthesis of the GeP electrodes are proposed for the first time. Such nanoreactors form a self-supported conductive network, ensuring sufficient electrolyte infiltration and fast electron transport. They restrain crystal growth and accommodate the volume expansion of GeP simultaneously. Reaction kinetics and confinement effect are optimized through nanoreactor size regulation. The optimized GeP electrode has high reversible capacities and outstanding cyclability and rate performance for sodium storage, outperforming most previously reported phosphides.

Rationalized atomic/clusters dispersion of Fe/Se/Al on interconnected N-doped carbon nanofibers for fast sodiation

The greater availability of sodium with large storage capacity motivates the fabrication of advanced electrodes materials for sodium ion batteries (SIBs) to promote in potential market of smart appliances. Multiple metals atomic dispersion into carbon framework can enhance the adsorption property of sodium for high performance SIBs. In this work, rationalized atomic/clusters of Fe/Se/Al are dispersed on N-doped amorphous carbon fibers through electrospinning and direct selenization (DS) processes. The developed product of DS-Fe/Se/Al@NC-650 nanofibers are employed as anode materials of SIBs, exhibitinga high specific capacity of 432 mAh g−1 at 100 mA g−1 a desirable cycling stability with a capacity retention of 99 % after 700 cycles. Such an excellent storage capacity initiates through synergistic effects of the uniformly distributed Fe/Se/Al and the interconnected nitrogen-doped carbon network. For the apprehension of capacity and stability of DS-Fe/Se/Al@NC-650 nanofibers for SIBs, the theoretical calculations were carried out and provide strong evidences which proves the electron/ion transport in experimental results.

Flexible all-solid-state supercapacitors based on boron and nitrogen-doped carbon network anchored on carbon fiber cloth

The rapid development of wearable electronic devices has created a huge demand for flexible all-solid-state supercapacitors (FSSCs), and high-performance electrode materials for FSSCs are strong desired simultaneously. In this work, boron and nitrogen-doped carbon (BCN) anchored on active carbon fiber cloth (ACC) are specially designed and manufactured by immersing ACC in a mixed solution of urea, boric acid and polyethylene oxide-propylene oxide (P123) and then calcining, which can be used to assemble high-performance FSSCs as electrodes. The three-dimensional (3D) cross-linked network of BCN grown on the carbon fibers improves the transmission rate of electrons and provides abundant electrochemical reaction sites, which are conducive to the performance of supercapacitors. Thanks to this structural advantage, the ACC@BCN electrode exhibits an area specific capacitance of 1018 mF cm−2 and a volume specific capacitance of 535.8 F g−1 at a current of 1 mA cm−2. Furthermore, the symmetric FSSCs based on ACC@BCN show high energy density of 1.573 mWh cm−3 and power density of 128.7 mW cm−3, and the capacitance retention can still keep 89.5% even after 10,000 cycles. This work provides a simple and effective way for large-scale preparation of high-performance, high-stability electrode materials for wearable electronic devices.

Phosphorus modification of cobalt-iron nanoparticles embedded in a nitrogen-doped carbon network for oxygen reduction reaction.

For the electrochemical reduction of oxygen the development of heteroatom-doped carbon-based transition metal catalysts has become a recognized strategy to replace traditional noble metal catalysts. In this work a catalyst consisting of CoFe nanoparticles encapsulated in N-doped carbon-based materials (NC) supported by carbon nanotubes (CNTs), i.e. Fe3Co1@NC/CNTs, was modified via treatment with a phosphate salt to synthesize a P-Fe3Co1@NC/CNTs catalyst. The P-Fe3Co1@NC/CNTs exhibits with 5.29 mA cm−2 an enhanced current density which is comparable to a Pt/C catalyst. In addition, a stability and methanol resistance better than the Pt/C catalyst were observed which is ascribed to the carbon encapsulation and the synergies between the two transition metals. Finally, the reaction mechanism of P-doping was studied and discussed. These results provide possible directions for carbon-based catalysts and doping with heteroatoms for the improvement of catalytic activity. Moreover, the zinc–air battery assembled with P-Fe3Co1@NC/CNTs as the air-cathode exhibited a high-power density of 73 mW cm−2, which is comparable to that of Pt/C (71 mW cm−2) and a specific capacity of 763 mA h g−1. The prepared catalyst could potentially serve to take the place of precious metal catalysts in rechargeable Zn–air batteries.

Three-dimensional NiCo2O4 nanowires encapsulated in nitrogen-doped carbon networks as a high-performance aptamer stabilizer for impedimetric ultrasensitive detection of hepatitis C virus core antigen

Recently, the performance of aptamer-based sensors has been greatly improved by the combination of aptamers with novel nanomaterials. Herein, the hierarchical porous 3D-NiCo2O4 nanowires, shelled with a thin layer of N-doped carbon (l) with sea-urchin-like morphology, were successfully prepared by a facile protocol. The 3D N-C@NiCo2O4 NWs combine the electrochemical advantages of Ni and Co species by exhibiting higher specific capacitance and active sites and also much higher conductivity. More significantly, the carbon layer improves the stability, conductivity and porosity of the nanowires. Benefiting from such a hierarchical structure, 3D N-C@NiCo2O4 NWs fit a large amount of surface area in a very small space. Therefore, the 3D N-C@NiCo2O4 NWs was applied in order to increase the hepatitis C virus core antigen (HCV) aptamer load on the electrode that significantly increased the sensitivity of the sensor. The electrochemical evaluations were proved that there exists a very good linear relationship between the charge transfer resistance (Rct) and HCV contents in the range of 0.5 fg mL−1 to 0.12 pg mL−1 with a low detection limit of 0.16 fg mL−1. Besides, it was in real biological samples that the aptasensor experienced superior detection recoveries which illustrated its high detection performance and feasibility for practicability.

Highly conductive Co3Se4 embedded in N-doped 3D interconnected carbonaceous network for enhanced lithium and sodium storage

Traditional cobalt selenides as active materials in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) would suffer from drastic volume expansions and large stacking effects, leading to a low cycling stability. In this work, we utilized a facile template method for preparing Co3Se4@N-CN (CSNC) that encapsulated Co3Se4 nanoparticles into 3D interconnected nitrogen-doped carbon network (N-CN). Satisfactorily, it possesses excellent cycling stability with enhanced lithium and sodium energy storage capacity. As an anode material in LIBs, CSNC exhibited a prominent reversible discharge performance of 1313.5 mAh g−1 after 100 cycles at 0.1 A g−1 and 835.6 mAh g−1 after 500 cycles at 1.0 A g−1. Interestingly, according to the analysis from cyclic voltammetry, the in-situ generated Se might provide extra capacity that leaded to a rising trend of capacity. When utilized as an anode in SIBs, CSNC delivered an outstanding capacity of 448.7 mAh g−1 after 100 cycles at 0.1 A g−1 and could retain 328.9 mAh g−1 (77.2% of that of 0.1 A g−1) even at a high current density of 5.0 A g−1. The results demonstrate that CSNC is a superior anode material in LIBs and SIBs with great promise. More importantly, this strategy opens up an effective avenue for the design of transition metal selenide/carbonaceous composites for advanced battery storage systems.

Efficient synthesis of Cu3P nanoparticles confined in 3D nitrogen-doped carbon networks as high performance anode for lithium/sodium-ion batteries

As a metal phosphide, copper phosphide (Cu3P) offers the advantages of low-cost, environmental friendliness, and excellent volumetric capacity. However, the development of Cu3P in lithium/sodium-ion batteries is limited by its poor conductivity, large volume change, and nano-crystal agglomeration. In this work, we prepared nano-scale Cu3P uniformly embedded in a nitrogen-doped three-dimensional (3D) porous carbon network (denoted as Cu3P/N-CN) through a simple and novel strategy of freeze-drying with NaCl crystals as template. The Cu3P nanoparticles effectively alleviated the physical strain generated during the charging and discharging processes and improved the utilization rate of the active material. Moreover, the 3D porous structure enhanced the conductivity, inhibited the agglomeration of the Cu3P nanoparticles, and facilitated the rapid diffusion of electrons/ions. The Cu3P/N-CN composite anode exhibited an outstanding rate capability (431.6 mAh g−1 at 3.0 A g−1), outstanding cyclic stability (752.3 mAh g−1 at 0.1 A g−1 over 100 cycles) for lithium storage, and excellent rate performance (220.0 mAh g−1 at 3.0 A g−1) and cycle performance (340.9 mAh g−1 at 0.1 A g−1 over 100 cycles) for sodium storage. This novel Cu3P/N-CN electrode thus has a promising application in energy storage technologies.

Rational design of efficient metal-free catalysts for peroxymonosulfate activation: Selective degradation of organic contaminants via a dual nonradical reaction pathway

Designing efficient and low-cost catalysts to activate peroxymonosulfate (PMS) to rapidly degrade organic contaminants is important for the practical applications of the advanced oxidation process. Herein, inspired by the water absorption process of the baby diaper, we design nitrogen-doped porous carbon network catalysts (N-PCNs) for peroxymonosulfate activate to degrade recalcitrant organic pollutants. The resulting product called nitrogen-doped porous carbon networks carbonized at 800 °C (N-PCN8) exhibits enhanced adsorption and catalytic activity due to its large specific surface area (1137.7 m2 g−1), highly graphitic degree, and high graphite N content (50.3%).4-CP (0.02 g/L) was completely degraded in 30 min by using N-PCN8 (0.2 g/L) and PMS (0.2 g/L). The catalytic system is efficient over a wide pH range (3–9) and shows strong resistance to interference with inorganic anions (Cl−, HCO3−, CO32−). Several aromatic pollutants, including 4-CP, BA, NB, HBA, CBZ, and BPA, are used as target pollutants to further evaluate the oxidative capacity of the system, and the degradation rate were 100%, 19.5%, 3.5%,5 5.7%, 79% and 100%, respectively. Results suggest that the system is selective for pollutants, and singlet oxygen oxidation and mediated electron transfer effects are the main causes of 4-CP degradation.

3D hierarchical porous nitrogen-doped carbon/Ni@NiO nanocomposites self-templated by cross-linked polyacrylamide gel for high performance supercapacitor electrode

Three-dimensional nitrogen-doped carbon network incorporated with nickel@nickel oxide core-shell nanoparticles composite (3D NC/Ni@NiO) has been facilely prepared, self-templated by the cross-linked polyacrylamide aerogel precursor containing NiCl2. Characterizations reveal that the Ni@NiO nanoparticles distribute homogeneously in the 3D nitrogen-doped carbon matrix and the composite is of hierarchical porous structure. When used as supercapacitor electrode in a three-electrode system, the 3D NC/Ni@NiO exhibits enhanced electrical conductivity and excellent electrochemical performance, presenting a high specific capacitance (389F g−1 at 5 mV s−1), good rate capability (276 F g−1 at 100 mV s−1) and outstanding cycling performance (with the capacitance retention of 70.2% after 5000 charge-discharge cycles). This is due to the synergistic effects of conductive metallic nickel, pseudocapacitive nickel oxide as well as in situ nitrogen doping of carbon network. Moreover, an asymmetric supercapacitor (ASC) was fabricated with NC/Ni@NiO as positive electrode and active carbon as negative electrode. The ASC device exhibits a maximum energy density of 19.4 W h kg−1 at a power density of 700 W kg−1 and shows good cycling stability (73.8% capacity retention after 3000 cycles), indicating that it has great promise for practical energy storage and conversion application.

Dendrite-free Zn anodes enabled by functional nitrogen-doped carbon protective layers for aqueous zinc-ion batteries.

Rechargeable aqueous zinc-ion batteries possess the merits of good environmental benignity, high operational safety and high energy density. Nevertheless, the practical application of zinc-ion batteries is severely obstructed by the inhomogeneous deposition of metallic Zn on the anode, which results in serious capacity fading, poor coulombic efficiency, and electrolyte consumption. Herein, we propose a simple strategy of constructing a functional nitrogen-doped carbon network coating layer on zinc foil for dendrite-free Zn stripping/plating. On one hand, the good conductivity of the artificial Zn/electrolyte interface can quickly balance the electric field and lower the nucleation overpotential. On the other hand, the porosity feature and functional groups of the protective layer can provide a fast Zn2+ transportation pathway and generate well-dispersed nucleation seeds. Therefore, the protective layer can effectively hamper the growth of metallic Zn dendrites and resist side reactions. The as-prepared N-C/Zn anode displays superior cycling stability (800 h at 2 mA cm-2 with the capacity of 2 mA h cm-2) and a satisfactory coulombic efficiency of 98.76% during the Zn stripping/plating process. A long cycle life and high specific capacity (162.10 mA h g-1 after 500 cycles at 2.0 A g-1) are also obtained for N-C/Zn||ZnSO4||V2O5 full cells. The strategy provides a facile and effective opportunity for constructing high-performance rechargeable aqueous zinc-ion batteries.

Ultrasmall metal oxide nanocrystals embedded in nitrogen-doped carbon networks based on one-step pyrolysis of bi-functional metallo-organic molecules for high-performance lithium-ion batteries

Commercial phthalocyanine dyes, including tin phthalocyanine and iron phthalocyanine, are employed as precursors to fabricate SnO2/Fe2O3 nanocrystals embedded in carbon framework by simple one-step in-situ pyrolysis. Phthalocyanine dyes are typical metallo-organic molecules incorporating N-containing conjugated organic shell and single metal atom core (Sn or Fe here), which can serve as the resources of both N-doped porous carbon and SnO2/Fe2O3 nanocrystals. Meanwhile, electronegative N atoms combined with rigid conjugated organic ligands is helpful for restricting the aggregation of metal ions during carbonization, leading to the generation of ultrasmall SnO2/Fe2O3 nanocrystals embedded in amorphous carbon framework (denoted as SnO2/N-PC and Fe2O3/N-PC). The obtained SnO2/N-PC and Fe2O3/N-PC have stable carbon continuous phase, ultrasmall and well-distributed metal oxide nanocrystals and porous skeleton, and then display superior lithium storage performance. SnO2/N-PC delivers high initial discharge and charge capacities of 1654 mAh g−1 and 1084 mAh g−1; after cycling for 200 times, it retains a reversible capacity of 775 mAh g−1, which is nearly 80% against the capacity of the second cycle. Fe2O3/N-PC presents high reversible capacity of 1123 mAh g−1 after 136 cycles at 200 mA g−1, and 612 mAh g−1 after 200 cycles at 1 A g−1.