N-doped Carbon Network Research Articles

Si nanoparticles embedded in porous N-doped carbon fibers as a binder-free and flexible anode for high-performance lithium-ion batteries

Si has attracted more attention as an ideal anode for next-generation Li-ion batteries (LIBs), due to its large theoretical capacity and low de-lithiation voltage. However, extreme volume change (about 300%) and low electronic conductivity severely hinder its practical application. Herein, to overcome these problems, via the electrospinning and pyrolysis processes, Si nanoparticles are embedded in porous N-doped carbon fibers (Si/P-NCFs) and interwoven into a flexible film. The binder-free and flexible Si/P-NCFs can significantly enhance the Li-ion storage capacity (1386 mAh g−1 after 100 cycles at 0.1 A g–1), cycling stability (942 mAh g−1 over 1000 cycles at 1 A g−1), as well as rate capability (381 mAh g−1 at 10 A g−1). These improvements are ascribed to the spatial confinement of carbon fibers and buffering effect of porous structure, which synergistically prevent the harm caused by the volume change. Additionally, porous N-doped carbon networks and binder-free structure can significantly enhance electron/ion conductivities. This work demonstrates an effective design to address the volume change and low electronic conductivity of Si towards advanced flexible Si-based anodes, as well as exhibits promising potential in practical use.

Dual-template synthesis of interconnected 3D hollow N-doped carbon network for electrochemical application

Dual-template synthesis of interconnected 3D hollow N-doped carbon network for electrochemical application

Sandwich-like SnO2/Cu@Carbon composites with long-term cycling stability as lithium-ion battery anodes

Tin-based anode materials have emerged as a promising candidate for lithium-ion batteries due to its inexpensive cost and high theoretical specific capacity, whereas its potential application is limited by severe capacity attenuation and inferior cycling stability due to the huge volume fluctuation during lithiation/delithiation. Herein, SnO2/[email protected] composite was fabricated to overcome this problem through a facile co-precipitation approach followed by carbon coating. In the as-prepared composite, SnO2 and Cu particles are uniformly embedded in N-doped carbon network matrix. Such unique sandwich-like product can greatly alleviate the large volume expansion and SnO2 aggregation that is conducive to the electron/ion migration, and significantly improve cycling permanence. Therefore, the optimized sample shows impressive long-term stability even at high current density of 1.0 A g−1 (348 mAh g−1 after 1000 loops without obvious capacity decay). Moreover, a comprehensive dynamic analysis of the lithium storage was performed, implying that the increased Li+ diffusion coefficient and pseudocapacitive contribution after cycling may account for the improved electrochemical performances.

3D electronic channels wrapped Large-Sized SnSe as flexible electrode for Sodium-Ion batteries

Transition metal selenides are regarded as the promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacitie. However, they still suffer from some fatal flaws including short lifetime and sluggish cycling kinetics. Herein, a free-standing, binder-free electrode was developed by electrospinning and subsequent thermal treatment process, in which three-dimensional (3D) N-doped carbon nanofibers and tin selenide are cross-linked with each other (SnSe/NCF). The synergistic effect of SnSe microsheets and carbon fibers shortens the ion transport channel and increases more active sites. N-doped carbon network not only improves electrical conductivity but also prevents pulverization of the material. The as-prepared SnSe/NCF electrodes exhibit good electrical conductivity and flexibility owing to the highly carbonized carbon nanofiber network. The SnSe/NCF electrode exhibits superior specific capacity with (576.7 mAh g−1 at 0.2 A g−1), ultra-long lifetime (286.4 mAh g−1 after 2100 cycles at 2.0 A g−1) and excellent rate performance (576.7 mAh g−1 at 5 A g−1) as a stand-alone anode for SIBs. This work provides a promising approach for developing flexible energy storage devices.

MOF-Derived Co and Fe Species Loaded on N-Doped Carbon Networks as Efficient Oxygen Electrocatalysts for Zn-Air Batteries

HighlightsA novel method is developed to prepare bifunctional oxygen electrocatalysts composed of Co nanoparticles and highly dispersed Fe loaded on N-doped carbon substrates by virtues of metal-organic frameworks and two different doping processes.The designed catalysts show comparable performance with commercial catalysts. Meanwhile, rechargeable Zn-air batteries with prepared catalysts demonstrate high peak power density and good cycling stability.The performance promotion originates from the synergy between Co nanoparticles and highly dispersed Fe, porous structures, large specific areas, and distinct three-dimensional carbon networks. Searching for cheap, efficient, and stable oxygen electrocatalysts is vital to promote the practical performance of Zn-air batteries with high theoretic energy density. Herein, a series of Co nanoparticles and highly dispersed Fe loaded on N-doped porous carbon substrates are prepared through a “double-solvent” method with in situ doped metal-organic frameworks as precursors. The optimized catalysts exhibit excellent performance for oxygen reduction and evolution reaction. Furthermore, rechargeable Zn-air batteries with designed catalysts demonstrate higher peak power density and better cycling stability than those with commercial Pt/C+RuO2. According to structure characterizations and electrochemical tests, the interaction of Co nanoparticles and highly dispersed Fe contributes to the superior performance for oxygen electrocatalysis. In addition, large specific surface areas, porous structures and interconnected three-dimensional carbon networks also play important roles in improving oxygen electrocatalysis. This work provides inspiration for rational design of advanced oxygen electrocatalysts and paves a way for the practical application of rechargeable Zn-air batteries.

Engineering Ag nanoparticles and amorphous MoOx on three dimensional N-doped carbon networks for enhanced lithium storage performance

Molybdenum-based oxides have been widely investigated as promising material for lithium ion batteries owing to their unique physical and chemical properties as well as the large specific capacities. However, the fast capacity fading and poor cyclability originated from the large volume expansion and the sluggish electrode kinetics still inhibit their practical application. Herein, Ag nanoparticles combined with amorphous MoOx-in-plane nanoconfined on three dimensional N-doped porous carbon networks (3DNC) are designed and synthesized through salt-template strategy accompanied by annealing treatment and hydrothermal method (3DNC-MoOx-Ag). The synergistic effect of Ag nanoparticles and amorphous MoOx can inhibit the “dead volume” and aggregation of the electrode, accommodate the volume change, accelerate the diffusion kinetics during the lithium ion intercalation and de-intercalation processes. As a result, the designed 3DNC-MoOx-Ag delivers prominent cycling stability (834 mAh g−1 after 100 cycles at 200 mA g−1) and excellent rate performance (419 mAh g−1 after 70 cycles at 5000 mA g−1). Even at 5000 mA g−1, a specific capacity as high as 369 mAh g−1 can be achieved after 500 cycles.

N-doped carbon networks as bifunctional electrocatalyst toward integrated electrochemical devices for Zn-air batteries driving microbial CO2 electrolysis cell

A simple pyrolysis route has been developed for fabrication of nitrogen-doped carbon networks (N-Cnet) that not only features a large number of mesoporous structures, but also holds high specific surface area and excellent conductivity. The as-developed N-Cnet performs impressively toward electrocatalysis of oxygen reduction reaction (ORR) and CO2 reduction reaction (CO2RR). For ORR in alkaline electrolyte, the N-Cnet manifests an initial potential of 0.95 V and half-wave potential of 0.86 V that are comparable to the benchmarked Pt/C catalysts. While for CO2RR, the N-Cnet shows a high selectivity for CO production with Faraday efficiency (FE) of as high as 95% and long-term stability. We further demonstrate the potential application of N-Cnet in electrochemical devices of zinc-air batteries (ZABs) and microbial CO2 electrolysis cell (MEC), the former is capable of releasing a maximum power density of 141 mW cm-2, while the later shows capability for efficiently converting CO2 into CO with the assistance of external voltage. We thus propose and set up an integrated proof-of-concept electrochemical device with ZABs driving MEC that can implement the feasibility of self-powered conversion of CO2 to value-added CO.

Catalytic Mo2C decorated N-doped honeycomb-like carbon network for high stable lithium-sulfur batteries

• Honeycomb-like porous hollow carbon network is successfully constructed. • Mo 2 C nanoparticles are embedded into carbon surface with high pyridinic N content. • Lithium sulfur batteries exhibit excellent cycling stability and rate capability. • Mo 2 C enhances the affinity toward polysulfide and accelerates its interconversion. Lithium sulfur (Li-S) batteries hold promise as next-generation high energy density devices due to their high theoretical capacities. However, their commercialization confronts great challenges, in particular the notorious shuttle effect and sluggish kinetics, making it difficult to realize high sulfur loading and cell energy density properties. Herein, we explore the potential of molybdenum carbide (Mo 2 C) as the cathode catalyst to promote the polysulfide conversion. Nanosized Mo 2 C embedded porous carbon network (Mo 2 C@PCN) are prepared through the pyrolysis of molybdenum and chitosan precursor. Both electrochemical performance and theoretical calculations reveal that introducing the Mo 2 C can not only enhance the affinity toward the polysulfide intermediate, but also significantly accelerate the polysulfide interconversion compared with that of the pristine porous carbon network (PCN), thereby endowing the Li-S batteries with excellent cycling stability with a low capacity decay of 0.034 % per cycle over 600 cycles, and superb rate capability of 644 mAh g −1 at 5 A g −1 .

Interfacial Engineered Vanadium Oxide Nanoheterostructures Synchronizing High-Energy and Long-Term Potassium-Ion Storage.

Potassium ion hybrid capacitors (KICs) have drawn tremendous attention for large-scale energy storage applications because of their high energy and power densities and the abundance of potassium sources. However, achieving KICs with high capacity and long lifespan remains challenging because the large size of potassium ions causes sluggish kinetics and fast structural pulverization of electrodes. Here, we report a composite anode of VO2–V2O5 nanoheterostructures captured by a 3D N-doped carbon network (VO2–V2O5/NC) that exhibits a reversible capacity of 252 mAh g–1 at 1 A g–1 over 1600 cycles and a rate performance with 108 mAh g–1 at 10 A g–1. Quantitative kinetics analyses demonstrate that such great rate capability and cyclability are enabled by the capacitive-dominated potassium storage mechanism in the interfacial engineered VO2–V2O5 nanoheterostructures. The further fabricated full KIC cell consisting of a VO2–V2O5/NC anode and an active carbon cathode delivers a high operating voltage window of 4.0 V and energy and power densities up to 154 Wh kg–1 and 10 000 W kg–1, respectively, surpassing most state-of-the-art KICs.

Interconnected N-Doped Carbon Network as High-Performance Anode Material for Superior Lithium Ion Hybrid Capacitor

Interconnected N-Doped Carbon Network as High-Performance Anode Material for Superior Lithium Ion Hybrid Capacitor

Optimization of tetracycline adsorption onto zeolitic–imidazolate framework-based carbon using response surface methodology

This study investigated the fabrication of zeolitic–imidazolate framework (ZIF-8) and ZIF-8-derived porous carbon and their application in the adsorptive removal of tetracycline from water. The materials were analysed by X-ray photoelectron spectroscopy, scanning electron microphotography, and the measurement of pH point of zero charge. The results indicated the presence of N-doped carbon network and functional groups on ZIF-8-derived porous carbon. Response surface methodology was used for statistical analysis. The effect of operating parameters involving tetracycline concentration (25–100 mg/L), dose (0.05–0.75 g/L), and pH (4–10) were conducted. The results indicated that the quadratic regression models were statistically significant and the parameters of tetracycline concentration and adsorbent dose profoundly affected the adsorption capacity. The optimum conditions for adsorption of tetracycline were suggested and verified. The highest tetracycline actual adsorption capacity obtained by ZIF-8 and ZIF-8-derived porous carbon were 171.3, and 339.06 mg/g, respectively. The study proposed the participation of hydrogen bonding and π–π interactions as main mechanism. With the high suitability, the response surface methodology can be an efficient optimization tool.

In situ formation of few-layered MoS2@N-doped carbon network as high performance anode materials for sodium-ion batteries

Molybdenum sulfide (MoS2) has become a promising anode material for sodium-ion batteries (SIBs) due to its unique two-dimensional layered structure and high theoretical capacity. However, the poor electrical conductivity and unceasing volume change of MoS2 electrode during charge/discharge process will result in its poor rate performance and rapid capacity fading. In this work, few-layered MoS2@N-doped carbon network (F-MoS2@NCN) was synthesized through a facile freeze drying and annealing process. The N-doped carbon network could effectively improve the charge transport ability and accommodate the volume change of MoS2, while the few-layered MoS2 structure could also shorten the Na+ diffusion pathway and improves its diffusion mobility during cycling process. Benefiting from the synergetic effects between N-doped carbon network and few-layered MoS2, F-MoS2@NCN could maintain a high reversible capacity of 354.0 mAh g−1 at 50 mA g−1 after 100 cycles and deliver a reversible capacity of 298.7 mAh g−1 at a current density of 1000 mA g−1. This work should provide new insights into MoS2-based anode materials for SIBs.

Constructing hierarchical carbon network wrapped Fe3Se4 nanoparticles for sodium ion storage and hydrogen evolution reaction

The hierarchical porous structure has been attracted increasing attention during the design of advanced electrode materials for energy storage and conversion fields. Herein, hierarchical N-doped carbon network wrapped Fe3Se4 nanoparticles (Fe3Se4 @NC@CNTs) has been successfully fabricated by a facile freeze-drying method followed by in situ selenization process. The macroporous with a diameter of about 200 nm uniformly distributed into the hierarchical carbon network, guaranteeing favorable electronic conductivity as well as structural stability. When utilized as anodes for sodium ion batteries, the Fe3Se4 @NC@CNTs exhibit a capacity of 440 mAh g−1 after 100 cycles at 100 mA g−1 (based on the total mass of the composite). Even cycling at 500 mA g−1 for 1000 cycles, the electrode still remains 311 mAh g−1. In addition, the Fe3Se4 @NC@CNTs also shows excellent hydrogen evolution reaction performance (an overpotential of 167 mV at 10 mA cm−2 and a Tafel slope of 68 mV dec−1). The superior electrochemical performance of the Fe3Se4 @NC@CNTs could be ascribed to the unique hierarchical network and uniform porous structure, which accommodates the volume changes of inner Fe3Se4, accelerates the ions/electrons transportation and facilitates electrolyte penetration. These results may give insights for the rational design of advanced electrode materials.

An Open Gate for High-Density Metal Ions in N-Doped Carbon Networks: Powering Fe–N–C Catalyst Efficiency in the Oxygen Reduction Reaction

Non-noble metal catalysts for the oxygen reduction reaction (ORR) showing catalytic activity comparable or even superior to that of the benchmark Pt/C are highly attractive systems for the development of a mature fuel cell technology. Fe–N–C moieties exhibit an optimal performance in the ORR although a synthetic strategy for their production still remains a challenging matter of catalysis and materials science. Herein, an original and general protocol for the preparation of high-density and discrete Fe–N–C-based single-atom catalysts has been proposed starting from cheap and food-grade raw components. The rational combination of chelating citrate ions with the ancillary monodentate thiocyanate (SCN–) ligand has established an “open gate” for water-soluble iron ions to be accommodated in the form of Fe–N–C moieties within the final C–N networks. Although recent findings in the field of electrocatalysis have pointed out the often beneficial synergistic action between isolated and metallic iron species or iron carbides and their protecting C–N shells, the poor selectivity on the nature of the final Fe species in N-doped C-networks remains a matter of debate and does not shed light on the effective nature of the active species in the process. The highly metal-loaded catalysts in the form of highly dispersed Fe–N–C moieties prepared with the synthetic protocol described in the paper have been tested as electrocatalysts in the ORR, showing electrocatalytic performance under an alkaline environment that ranks among the highest reported so far for related Fe single-atom catalysts (Fe-SACs) of the state-of-the-art.

NiCoP nanowire arrays embedded in 3D integrated N-doped carbon network for enhanced electrochemical oxygen evolution

Controllable construction of self-supporting electrodes with efficient charge migration on the whole electrode and abundant electrocatalytic active sites is still challenging in oxygen evolution reaction (OER). Here, an intentionally designed self-supporting electrode consisting of NiCoP nanowire arrays embedded in 3D integrated N-doped carbon network (NiCoP@NC-NCNTs) is fabricated for high-performance electrocatalytic OER. The NiCoP@NC-NCNTs has been prepared via in-situ growth of N-doped carbon nanotubes (NCNTs) and N-doped carbon (NC) layer on NiCo arrays and subsequent phosphating reaction. Due to the intertwined network structure of NCNTs and the conformal coating of NC layer on the surface of NiCoP arrays, the NiCoP@NC-NCNTs catalyst not only realizes effective charge migration on the whole electrode, but also offers abundant catalytic active sites. Compared to NiCoP nanowire arrays without embedding in 3D carbon network, the NiCoP@NC-NCNTs exhibits a remarkable performance for electrocatalytic OER, in terms of an ultralow overpotential of 227 mV at 10 mA cm−2, and 317 mV even at 100 mA cm−2. Meanwhile, a negligible current degradation can be found in the chronoamperometric (i-t) curve after the long-term stability test. This work proves that it is a promising strategy to develop electrocatalysts by embedding the bimetallic phosphides in 3D carbon networks.

Nanoconfined ReS2 in biomass-derived 3D porous N-doped carbon architecture as anode for stable lithium-ion storage

Rhenium disulfide (ReS2) has emerged as a promissing host material toward energy storage for its distinctive electronic, optical, and mechanical features. Nevertheless, structural damage during repeated charge-discharges and inferior conductivity have severely impaired the electrochemical performance of ReS2. Effective incorporation with carbon component is a feasible pathway to cope with these issues. In this work, employing glucosamine as carbon and nitrogen sources, small ReS2 nanoparticles are easily encapsulated into hierarchical porous N-doped carbon networks to obtain ReS2NC hybrids via a freeze-drying and subsequent annealing method. The hierarchical porous structure and the confining effect of carbon matrix on ReS2 nanoparticles can effectively inhibit the aggregation, maintain the structural stability as well as guarantee the rapid ion diffusion and electron transfer. As a consequence, ReS2NC hybrid anode achieves an extremely improved electrochemical property for lithium-storage. The optimized ReS2NC electrode can remain a high capacity of ~676 mAh g−1 as 500 cycles under 0.1 A g−1 are completed. Besides, as it cycles for 500 loops under 1 A g−1, a capacity of ~387 mAh g−1 is still kept, demonstrating enhanced rate capability.

Fe3C-inserted “tube plugging into porous network” nanohybrids as advanced sulfur hosts for lithium-sulfur batteries

Commercial applications of lithium-sulfur batteries are hindered by the low electrical conductivity of sulfur cathodes, which can be overcome by the application of suitable sulfur host materials. In this work, a novel and effective method is developed to grow bamboo-like N-doped carbon nanotubes (NCNTs) across three-dimensional N-doped porous carbon network (NPCNs) via chemical vapor deposition, thereby successfully preparing the sulfur-loaded composite carbon material inserted into the porous network. In such structure, carbon nanotubes act as electronic conduction paths, carbon networks as mass transfer channels, as well as the inserted Fe3C nanoparticles can increase the polarity of the carbon matrix. The discharge capacity of the S-NCNT/NPCNs cathode, as high as 1125 mAh g−1 at 0.2 C, retains 43.5% of its value when the current is increased 10-fold to 2 C. A specific capacity of 548.1 mAh g−1 at 1 C remains almost unchanged after 300 cycles, demonstrating better charge and discharge performance and excellent cycling ability of these promising candidate materials for Li-S battery applications. More importantly, the synthesis strategy is universal and can be fully extended to prepare other units, even binary NCNT/NPCNs (for example, NCNT/NPCNs-Co, NCNT/NPCNs-Co-Fe, NCNT/NPCNs-Fe-Ni, and NCNT/NPCNs-Co-Ni). The new strategy provided here may open up new ways for the application of hybrid carbon nanostructures in energy storage systems.

Three-dimensional porous ultrathin carbon networks reinforced PBAs-derived electrocatalysts for efficient oxygen evolution

Prussian blue analogues (PBAs), identified with a face-centered cubic (fcc) unit cell with transition-metal ions bridged by cyano ligands, can be used as precursors in nanomaterials for catalysis applications, but the performance is usually limited by the original large size of PBAs. We provide here a controllable thermal decomposition route for PBAs to obtain highly dispersed small-sized nanoparticles with high catalytic activity. CoFe PBA nanocubes as catalyst precursors are grown within three-dimensional porous ultrathin N-doped carbon networks (3DNC), which is constructed using mixed soluble salts as templates. The use of 3DNC as supporting matrix can not only increase the electrical conductivity and transport properties of reaction-relevant species within the catalyst material, but also supply huge specific surface and restrict the size of loaded nanoparticles. Followed by calcination in the reductive atmosphere, the PBA nanocubes are decomposed to form numerous small-sized CoFe/CoFeOx nanoparticles that are uniformly dispersed. It is interesting to find that this thermal decomposition process is assisted by 3DNC matrix because of its excellent thermal conductive property. Benefiting from the synergetic bimetal alloy/oxide composition, advantageous structural feature and favorable interfacial integration of the hybrid material, the CoFe/CoFeOx@3DNC exhibits remarkable electrocatalytic activity and stability for the oxygen evolution reaction (OER) in alkaline media. The decomposition of PBAs precursor to small-sized nanoparticles and the use of 3DNC as supporting matrix and thermal conductive agent are appealing. The integration of these two components provides an interesting hybrid catalyst system with controllable composition, delicate morphology and favorable interfacial property.

One-pot synthesis of ultrafine Pt-decorated MoS2/N-doped carbon composite with sponge-like morphology for efficient hydrogen evolution reaction

Ultrafine Pt-decorated interlayer-expanded MoS2/N-doped carbon composite with sponge-like morphology (Pt–MoS2/CN) has been synthesized through a one-pot pyrolysis protocol. Using PVP modified Pt colloidal as precursor not only avoids the formation of large Pt particles, but also plays an important role in the formation of highly dispersed interlayer-expanded MoS2 nanocrystalline within N-doped carbon network. The synergy between Pt nanoparticle and interlayer-expended MoS2 nanocrystalline gives rise to favorable intrinsic catalytic activity. The resulting Pt-MoS2/CN composite boosts the hydrogen evolution reaction (HER) performance to an upper level in acidic media with low overpotential (−20 mV at 10 mA cm−2), high exchange current density (6.24 mA cm−2) and much stable durability (more than 80 h). All these properties can be compared with that of commercial Pt/C catalyst. The excellent electrocatalytic performance, simple preparation and low cost make it a promising candidate for HER.

Facile synthesis of V2O3@N-doped carbon nanosheet arrays on nickel foam as free-standing electrode for high performance lithium ion batteries

Novel hierarchically structured V2O3@N-doped carbon nanosheet arrays on nickel foam (V2O3@NC NANF) was fabricated by simple solvothermal reaction and subsequently calcination process. The porous nanosheet arrays are constructed by V2O3 nanoparticles that is uniformly coated with conductive N-doped carbon network. The V2O3@NC NANF was used as a free-standing anode without binder and conductive additives for lithium-ion batteries (LIBs). It exhibits a reversible capacity of 892 mA h g−1 at 0.1 A g−1 after cycling 400 times. After 1000 cycles, it shows a discharge capacity of 317 mA h g-1 at 2 A g−1. The superior electrochemical performance is attributed to the hierarchical structure and uniform N-doped carbon coated network, which can increase the conductivity and alleviate the volume expansion of the electrode. In addition, the influence of non-electrochemical active substances (binder and conductive additives) is removed, and the electrical contact between active material and nickel foam collector is enhanced, thus further improving the electrochemical performance.