High-performance Pt catalysts supported on hierarchical nitrogen-doped carbon nanocages for methanol electrooxidation

Hierarchical nitrogen-doped carbon nanocages （hNCNC） with large specific surface areas were used as a catalyst support to immobilize Pt nanoparticles by a microwave-assisted polyol method. The Pt/hNCNC catalyst with 20 wt% loading has a homogeneous dispersion of Pt nanoparticles with the average size of 3.3 nm, which is smaller than 4.3 and 4.9 nm for the control catalysts with the same loading supported on hierarchical carbon nanocages （hCNC） and commercial Vulcan XC-72, respec- tively. Accordingly, Pt/hNCNC has a larger electrochemical surface area than Pt/hCNC and Pt/XC-72. The Pt/hNCNC catalyst exhibited excellent electrocatalytic activity and stability for methanol oxidation, which was better than the control catalysts. This was attributed to the en- hanced interaction between Pt and hNCNC due to nitrogen participation in the anchoring function. By making use of the unique advantages of the hNCNC support, a heavy Pt loading up to 60 wt% was prepared without serious agglomeration, which gave a high peak-current density per unit mass of catalyst of 95.6 mA/mg for achieving a high power density. These results showed the potential of the Pt/hNCNC catalyst for methanol oxidation and of the new hNCNC support for wide applications.

A direct electrochemical biosensor for rapid glucose detection based on nitrogen-doped carbon nanocages

Given the increasing number of diabetic patients,rapid and accurate detection of glucose in body fluids is critical.This study developed a direct electrochemical biosensor for glucose based on nitrogen-doped carbon nanocages(NCNCs).NCNCs possess a large specific surface area of 1395 m^(2)·g^(-1),a high N atomic content of 9.37%and good biocompatibility,which is favorable for enzyme loading and electron transfer.The surface average concentration of electroactive glucose oxidase on NCNCs was 2.82×10^(-10)mol·cm^(-2).The NCNC-based direct electrochemical biosensor exhibited a high sensitivity of 13.7μA·(mmol·L^(-1))^(-1)·cm^(-2),rapid response time of 5 s and an impressive electron-transferrate constant(ks)of 1.87 s^(-1).Furthermore,we investigated an NCNC-based direct electron transfer(DET)biosensor for sweat glucose detection,which demonstrated tremendous promise for non-invasive wearable diabetes diagnosis.

Alloyed Pt-Sn nanoparticles on hierarchical nitrogen-doped carbon nanocages for advanced glycerol electrooxidation

Glycerol is an alternative sustainable fuel for fuel cells,and efficient electrocatalyst is crucial for glycerol oxidation reaction(GOR).The promising Pt catalysts are subject to the inadequate capability of C-C bond cleavage and the susceptibility to poisoning.Herein,Pt-Sn alloyed nanoparticles are immobilized on hierarchical nitrogen-doped carbon nanocages(hNCNCs)by convenient ethylene glycol reduction and subsequent thermal reduction.The optimal Pt_(3)Sn/hNCNC catalyst exhibits excellent GOR performance with a high mass activity(5.9 A·mg_(Pt)^(-1)),which is 2.7 and 5.4 times higher than that of Pt/hNCNC and commercial Pt/C,respectively.Such an enhancement can be mainly ascribed to the increased anti-poisoning and C-C bond cleavage capability due to the Pt_(3)Sn alloying effect and Sn-enriched surface,the high dispersion of Pt_(3)Sn active species due to N-participation,as well as the high accessibility of Pt_(3)Sn active species due to the three-dimensional(3D)hierarchical architecture of hNCNC.This study provides an effective GOR electrocatalyst and convenient approach for catalyst preparation.

Carbon nanocages bridged with graphene enable fast kinetics for dual-carbon lithium-ion capacitors

Lithium-ion capacitors(LICs) combining the advantages of lithium-ion batteries and supercapacitors are considered a promising nextgeneration energy storage device. However, the sluggish kinetics of battery-type anode cannot match the capacitor-type cathode, restricting the development of LICs. Herein, hierarchical carbon framework(HCF) anode material composed of 0D carbon nanocage bridged with 2D graphene network are developed via a template-confined synthesis process. The HCF with nanocage structure reduces the Li^(+) transport path and benefits the rapid Li^(+) migration, while 2D graphene network can promote the electron interconnecting of carbon nanocages. In addition, the doped N atoms in HCF facilitate to the adsorption of ions and enhance the pseudo contribution, thus accelerate the kinetics of the anode. The HCF anode delivers high specific capacity, remarkable rate capability. The LIC pouch-cell based on HCF anode and active HCF(a-HCF) cathode can provide a high energy density of 162 Wh kg^(-1) and a superior power density of 15.8 kW kg^(-1), as well as a long cycling life exceeding 15,000cycles. This study demonstrates that the well-defined design of hierarchical carbon framework by incorporating 0D carbon nanocages and 2D graphene network is an effective strategy to promote LIC anode kinetics and hence boost the LIC electrochemical performance.

Advanced Electro-active Dry Adhesive Actuated by an Artificial Muscle Constructed from an Ionic Polymer Metal Composite Reinforced with Nitrogen-doped Carbon Nanocages

An advanced electro-active dry adhesive, which was composed of a mushroom-shaped tibrillar dry adhesive array actuated by an Ionic Polymer Metal Composite （IPMC） artificial muscle reinforced with nitrogen-doped carbon nanocages （NCNCs）, was developed to imitate the actuation of a gecko＇s toe. The properties of the NCNC-reinforced Nation membrane, the electro- mechanical properties of the NCNC-reinforced IPMC, and the related electro-active adhesion ability were investigated. The NCNCs were uniformly dispersed in the 0.1 wt% NCNC/Nafion membrane, and there was a seamless connection with no clear interface between the dry adhesive and the IPMC. Our 0.1 wt% NCNC/Nation-IPMC actuator shows a displacement and force that are 1.6 - 2 times higher than those of the recast Nafion-IPMC. This is due to the increased water uptake （25.39%） and tensile strength （24.5 MPa） of the specific 3D hollow NCNC-reinforced Nation membrane, as well as interactions between the NCNCs and the sulfonated groups of the Nation. The NCNC/Nation-IPMC was used to effectively actuate the mushroom-shaped dry adhesive. The normal adhesion forces were 7.85 raN, 12.1 mN, and 51.7 mN at sinusoidal voltages of 1.5 V, 2.5 V, and 3.5 V, respectively, at 0.1 Hz. Under the bionic leg trail, the normal and shear forces were approximately 713.5 mN （159 mN·cm^-2） and 1256.6 mN （279 mN·cm^-2）, respectively, which satisfy the required adhesion. This new electro-active dry adhesive can be applied for active, distributed actuation and flexible grip in robots.

Boosting oxygen reduction activity of spinel CoFe2O4 by strong interaction with hierarchical nitrogen-doped carbon nanocages

The unique hierarchical nitrogen-doped carbon nanocages(h NCNC) are used as a new support to homogeneously immobilize spinel Co Fe_2O_4 nanoparticles by a facile solvothermal method. The so-constructed hierarchical Co Fe_2O_4/h NCNC catalyst exhibits a high oxygen reduction activity with an onset potential of0.966 V and half-wave potential of 0.819 V versus reversible hydrogen electrode, far superior to the corresponding 0.846 and 0.742 V for its counterpart of Co Fe_2O_4/h CNC with undoped hierarchical carbon nanocages(h CNC) as the support, which locates at the top level for spinel-based catalysts to date.Consequently, the Co Fe_2O_4/h NCNC displays the superior performance to the Co Fe_2O_4/h CNC, when used as the cathode catalysts in the home-made Al-air batteries. X-ray photoelectron spectroscopy characterizations reveal the more charge transfer from Co Fe_2O_4 to h NCNC than to h CNC, indicating the stronger interaction between Co Fe_2O_4 and h NCNC due to the nitrogen participation. The enhanced interaction and hierarchical morphology favor the high dispersion and modification of electronic states for the active species as well as the mass transport during the oxygen reduction process, which plays a significant role in boosting the electrocatalytic performances. In addition, we noticed the high sensitivity of O 1 s spectrum to the particle size and chemical environment for spinel oxides, which is used as an indicator to understand the evolution of ORR activities for all the Co Fe_2O_4-related contrast catalysts. Accordingly,the well-defined structure-performance relationship is demonstrated by the combination of experimental characterizations with theoretical calculations. This study provides a promising strategy to develop efficient, inexpensive and durable oxygen reduction electrocatalysts by tuning the interaction between spinel metal oxides and the carbon-based supports.

Effective enhancement of electrochemical energy storage of cobalt-based nanocrystals by hybridization with nitrogen-doped carbon nanocages

Cobalt-based oxygenic compounds Co(OH)2,CoO and Co3 O4 are attractive for electrochemical energy storage owing to their high theoretical capacities and pseudocapacitive properties.Despite the great efforts to their compositional and morphological regulations,the performances to date are still quite limited owing to the low active surface area and sluggish charge transfer kinetics.Herein,different Co-based nanocrystals(Co-NCs)were conveniently anchored on the hierarchical nitrogen-doped carbon nanocages(hNCNCs)with high specific surface area and coexisting micro-meso-macropores to decrease the size and facilitate the charge transfer.Accordingly,a high specific capacity of1170 Fg^-1 is achieved at 2 Ag^-1 for the Co(OH)2/hNCNCs hybrid,in which the capacitance of Co(OH)2(2214 F gco(OH)2)is approaching to its theoretical maximum(2595 Fg^-1),demonstrating the high utilization of active materials by the hybridization with N-doped nanocarbons.This study also reveals that these Co-NCs store/release electrical energy via the same reversible redox reaction despite their different pristine compositions.This insight on the energy storage of Co-based nanomaterials suggests that the commonly-employed transformation of the Co-NCs from Co(OH)2 to CoO and Co3 O4 on carbon supports is unnecessary and even could be harmful to the energy storage performance.The result is instructive to develop high-energy-density electrodes from transition metal compounds.

Low-Temperature Carbonized Nitrogen-Doped Hard Carbon Nanofiber Toward High-Performance Sodium-Ion Capacitors

Carbon nanofiber(CNF)was widely utilized in the field of electrochemical energy storage due to its superiority of conductivity and mechanics.However,CNF was generally prepared at relatively high temperature.Herein,nitrogen-doped hard carbon nanofibers(NHCNFs)were prepared by a lowtemperature carbonization treatment assisted with electrospinning technology.Density functional theory analysis elucidates the incorporation of nitrogen heteroatoms with various chemical states into carbon matrix would significantly alter the total electronic configurations,leading to the robust adsorption and efficient diffusion of Na atoms on electrode interface.The obtained material carbonized at 600°C(NHCNF-600)presented a reversible specific capacity of 191.0 mAh g^(−1)and no capacity decay after 200 cycles at 1 A g^(−1).It was found that the sodium-intercalated degree had a correlation with the electrochemical impedance.A sodium-intercalated potential of 0.2 V was adopted to lower the electrochemical impedance.The constructed sodium-ion capacitor with activated carbon cathode and presodiated NHCNF-600 anode can present an energy power density of 82.1 Wh kg^(−1)and a power density of 7.0 kW kg^(−1).

Nitrogen-doped porous carbon nanosheets as both anode and cathode for advanced potassium-ion hybrid capacitors

Potassium-ion hybrid capacitors(PIHCs)as a burgeoning research hotspot are an ideal replacement for lithium-ion hybrid capacitors(LIHCs).Here,we report nitrogen-doped porous carbon nanosheets(NPCNs)with enlarged interlayer spacing,abundant defects,and favorable mesoporous structures.The structural changes of NPCNs in potassiation and depotassiation processes are analyzed by using Raman spectroscopy and transmission electron microscopy.Due to the unique structure of NPCNs,the PIHC device assembled using NPCNs as both the anode and cathode material(double-functional self-matching material)exhibits a superior energy density of 128 Wh kg^(-1)with a capacity retention of 90.8%after 9000 cycles.This research can promote the development of double-functional self-matching materials for hybrid energy storage devices with ultra-high performance.

PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.However,such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores,in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support.Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers.Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential(E_(1/2))of 0.911 V versus reversible hydrogen electrode(vs.RHE)and enhanced durability with only decreasing 11 mV after 30,000 potential cycles,compared to a more significant drop of 24 mV in E_(1/2)of Pt/C catalysts(after 10,000 potential cycling).Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support,inhibiting the migration and aggregation of NPs during the ORR.

Preparation of nitrogen-doped carbon nanoblocks with high electrocatalytic activity for oxygen reduction reaction in alkaline solution

The oxygen reduction reaction （ORR） is traditionally performed using noble‐metals catalysts, e.g. Pt. However, these metal‐based catalysts have the drawbacks of high costs, low selectivity, poor stabili‐ties, and detrimental environmental effects. Here, we describe metal‐free nitrogen‐doped carbon nanoblocks （NCNBs） with high nitrogen contents （4.11%）, which have good electrocatalytic proper‐ties for ORRs. This material was fabricated using a scalable, one‐step process involving the pyrolysis of tris（hydroxymethyl）aminomethane （Tris） at 800℃. Rotating ring disk electrode measurements show that the NCNBs give a high electrocatalytic performance and have good stability in ORRs. The onset potential of the catalyst for the ORR is-0.05 V （vs Ag/AgCl）, the ORR reduction peak potential is-0.20 V （vs Ag/AgCl）, and the electron transfer number is 3.4. The NCNBs showed pronounced electrocatalytic activity, improved long‐term stability, and better tolerance of the methanol crosso‐ver effect compared with a commercial 20 wt%Pt/C catalyst. The composition and structure of, and nitrogen species in, the NCNBs were investigated using Fourier‐transform infrared spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. The pyroly‐sis of Tris at high temperature increases the number of active nitrogen sites, especially pyridinic nitrogen, which creates a net positive charge on adjacent carbon atoms, and the high positive charge promotes oxygen adsorption and reduction. The results show that NCNBs prepared by pyrolysis of Tris as nitrogen and carbon sources are a promising ORR catalyst for fuel cells.

Hierarchical sulfur and nitrogen co-doped carbon nanocages as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air battery

Exploring inexpensive and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) is critical for rechargeable metal-air batteries. Herein, we report a new 3D hierarchical sulfur and nitrogen co-doped carbon nanocages(hSNCNC) as a promising bifunctional oxygen electrocatalyst by an in-situ MgO template method with pyridine and thiophene as the mixed precursor. The as-prepared h SNCNC exhibits a positive half-wave potential of 0.792 V(vs. reversible hydrogen electrode, RHE) for ORR, and a low operating potential of 1.640 V at a 10 mA cm-2 current density for OER. The reversible oxygen electrode index is 0.847 V, far superior to commercial Pt/C and IrO2,which reaches the top level of the reported bifunctional catalysts. Consequently, the hSNCNC as air cathodes in an assembled Zn-air battery features low charge/discharge overpotential and long lifetime. The remarkable properties arises from the introduced multiple heteroatom dopants and stable 3D hierarchical structure with multi-scale pores, which provides the abundant uniform high-active S and N species and efficient charge transfer as well as mass transportation. These results demonstrate the potential strategy in developing suitable carbon-based bi-/multi-functional catalysts to enable the next generation of the rechargeable metal-air batteries.

Hierarchically porous nitrogen-doped carbon as cathode for lithium–sulfur batteries

Porous nitrogen-doped carbon is an especially promising material energy storage due to its excellentconductivity, stable physicochemical properties, easy processability, controllable porosity and low price.Herein, we reported a novel well-designed hierarchically porous nitrogen-doped carbon （HPNC） via acombination of salt template （ZnC12） and hard template （SiO2） as sulfur host for lithium-sulfur batter-ies. The low-melting ZnC12 is boiled off and leaves behind micropores and small size mesopores duringpyrolysis process, while the silica spheres are removed by acid leaching to generate interconnected 3Dnetwork of macropores. The HPNC-S electrode exhibits an initial specific capacity of 1355 mAh g^-l at 0.IC （IC= 1675 mAh g^-1 ）, a high-rate capability of 623 mAh g-l at 2 C, and a small decay of 0.13% per cycleover 300 cycles at 0.2 C. This excellent rate capability and remarkable long-term cyclability of the HPNC-Selectrode are attributed to its hierarchical porous structures for confining the soluble lithium polysulfideas well as the nitrogen doping for high absorbability of lithium polysulfide.

Hollow cobalt oxide nanoparticles embedded in nitrogen-doped carbon nanosheets as an efficient bifunctional catalyst for Zn–air battery

Rational design of low-cost, highly electrocatalytic activity, and stable bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) has been a great significant for metal–air batteries. Herein, an efficient bifunctional electrocatalyst based on hollow cobalt oxide nanoparticles embedded in nitrogen-doped carbon nanosheets(Co/N-Pg) is fabricated for Zn–air batteries. A lowcost biomass peach gum, consisting of carbon, oxygen, and hydrogen without other heteroatoms, was used as carbon source to form carbon matrix hosting hollow cobalt oxide nanoparticles. Meanwhile, the melamine was applied as nitrogen source and template precursor, which can convert to carbon-based template graphitic carbon nitride by polycondensation process. Owing to the unique structure and synergistic effect between hollow cobalt oxide nanoparticles and Co-N-C species, the proposal Co/N-Pg catalyst displays not only prominent bifunctional electrocatalytic activities for ORR and OER, but also excellent durability. Remarkably, the assembled Zn–air battery with Co/N-Pg air electrode exhibited a low discharge-charge voltage gap(0.81 V at 50 mA cm^-2) and high peak power density(119 mW cm^-2) with long-term cycling stability. This work presents an effective approach for engineering transition metal oxides and nitrogen modified carbon nanosheets to boost the performance of bifunctional electrocatalysts for Zn–air battery.

Highly Dispersed Cobalt Nanoparticles Embedded in Nitrogen-Doped Graphitized Carbon for Fast and Durable Potassium Storage

Potassium-ion batteries(KIBs)have great potential for applications in large-scale energy storage devices.However,the larger radius of K+leads to sluggish kinetics and inferior cycling performance,severely restricting its practical applicability.Herein,we propose a rational strategy involving a Prussian blue analogue-derived graphitized carbon anode with fast and durable potassium storage capability,which is constructed by encapsulating cobalt nanoparticles in nitrogen-doped graphitized carbon(Co-NC).Both experimental and theoretical results show that N-doping effectively promotes the uniform dispersion of cobalt nanoparticles in the carbon matrix through Co-N bonds.Moreover,the cobalt nanoparticles and strong Co-N bonds synergistically form a threedimensional conductive network,increase the number of adsorption sites,and reduce the diffusion energy barrier,thereby facilitating the adsorption and the diffusion kinetics.These multiple effects lead to enhanced reversible capacities of 305 and 208.6 mAh g^−1 after 100 and 300 cycles at 0.05 and 0.1 A g^−1,respectively,demonstrating the applicability of the Co-NC anode for KIBs.

Controllable synthesis of nitrogen-doped porous carbon from metal-polluted miscanthus waste boosting for supercapacitors

High-value reclamation of metal-polluted plants involved in phytoremediation is a big challenge.In this study,nitrogen-doped nanoporous carbon with large specific area of 2359.1 m^(2)g^(-1) is facilely fabricated from metal-polluted miscanthus waste for efficient energy storage.The synergistic effect of KOH,urea and ammonia solution greatly improve the nitrogen quantity and surface area of the synthesized carbon.Electrodes fabricated with this carbon exhibit the excellent capacitance performance of 340.2 F g^(-1) at 0.5 A g^(-1) and a low combined resistance of 0.116Ω,which are competitive with most of previously reported carbon-based electrodes.In addition,the as-obtained carbon electrode shows a high specific capacitance retention of over 99.6%even after 5000 cycles.Furthermore,the symmetric supercapacitor fabricated using the synthesized carbon achieves a superior energy density of 25.3 Wh kg^(-1)(at 400 W kg^(-1))in 1 mol L^(-1) Na_(2)SO_(4)aqueous solution.This work provides an efficient route to upcycle metal-polluted plant waste for supercapacitor applications.

Novel Ag@Nitrogen-doped Porous Carbon Composite with High Electrochemical Performance as Anode Materials for Lithium-ion Batteries

A novel Ag@nitrogen-doped porous carbon(Ag-NPC) composite was synthesized via a facile hydrothermal method and applied as an anode material in lithium-ion batteries(LIBs). Using this method, Ag nanoparticles(Ag NPs) were embedded in NPC through thermal decomposition of Ag NO_3 in the pores of NPC. The reversible capacity of Ag-NPC remained at 852 m Ah g^(-1)after 200 cycles at a current density of 0.1 A g^(-1), showing its remarkable cycling stability. The enhancement of the electrochemical properties such as cycling performance,reversible capacity and rate performance of Ag-NPC compared to the NPC contributed to the synergistic effects between Ag NPs and NPC.

Nitrogen-doped ordered mesoporous carbon:Effect of carbon precursor on oxygen reduction reactions

Aniline,pyrrole and phenanthroline,which have different nitrogen compositions,are used as carbon precursors to synthesize nitrogen-doped ordered mesoporous carbons（NOMCs） by the nanocasting method.The effect of the precursor on the resultant NOMC is extensively investigated by nitrogen adsorption-desorption measurements,scanning electron microscopy,X-ray photoelectron spectroscopy（XPS）,cyclic voltammetry and rotating ring-disk electrode measurements.Salient findings are as follows.First,the precursor has a significant influence on the specific surface area and textural properties.The NOMC materials derived from pyrrole（C-PY-900：765 m^2/） and phenanthroline（C-Phen-900：746 m^2/） exhibit higher specific surface areas than the aniline analog（C-PA-900：569 m^2/）.Second,the XPS results indicate that the total nitrogen content（ca.3.1–3.3 at%） is similar for the three carbon sources,except for a slight difference in the nitrogen configuration.Furthermore,the content of the nitrogen-activated carbon atoms is found to closely depend on the precursor,which is the highest for the phenanthroline-derived carbon.Third,the electrochemical results reveal that the electrocatalytic activity follows in the order C-PA-900 C-PY-900 C-Phen-900,confirming that the nitrogen-activated carbon atoms are the active sites for the oxygen reduction reaction（ORR）.In summary,the precursor has considerable influence on the composition and textural properties of the NOMC materials,of which the ORR electrocatalytic activity can be enhanced through optimization of the NOMCs.

Electrocatalytic hydrogen peroxide formation on mesoporous non-metal nitrogen-doped carbon catalyst

Direct electrochemical formation of hydrogen peroxide（H2O2） from pure O2 and H2on cheap metal-free earth abundant catalysts has emerged as the highest atom-efficient and environmentally friendly reaction pathway and is therefore of great interest from an academic and industrial point of view. Very recently,novel metal-free mesoporous nitrogen-doped carbon catalysts have attracted large attention due to the unique reactivity and selectivity for the electrochemical hydrogen peroxide formation [1–3]. In this work,we provide deeper insights into the electrocatalytic activity, selectivity and durability of novel metal-free mesoporous nitrogen-doped carbon catalyst for the peroxide formation with a particular emphasis on the influence of experimental reaction parameters such as p H value and electrode potential for three different electrolytes. We used two independent approaches for the investigation of electrochemical hydrogen peroxide formation, namely rotating ring-disk electrode（RRDE） technique and photometric UV–VIS technique. Our electrochemical and photometric results clearly revealed a considerable peroxide formation activity as well as high catalyst durability for the metal-free nitrogen-doped carbon catalyst material in both acidic as well as neutral medium at the same electrode potential under ambient temperature and pressure. In addition, the obtained electrochemical reactivity and selectivity indicate that the mechanisms for the electrochemical formation and decomposition of peroxide are strongly dependent on the p H value and electrode potential.

Nitrogen-doped hierarchical porous carbon from polyaniline/silica self-aggregates for supercapacitor

In this paper, nitrogen-doped hierarchical porous carbon(N-HPC) was prepared from polyaniline(PANI)/silica self-aggregates. H-bonding between N\\H groups in aniline/PANI and \\OH groups in nano silica template led to a self-assembly type, which enabled the formation of uniform N-HPC nanoparticles. Silica self-aggregates provided macroporous channels resulted in a decreased diffusion distance. After removing the hard template,the N-HPC had a high surface area(899 m^2·g^(-1)). Owing to two co-existed synergetic energy-storage mechanisms and the hierarchical porous structure, the obtained N-HPC exhibited a high specific capacitance of 218.75 F·g^(-1) at 0.5 A·g^(-1), compared with the nonporous nitrogen-doped carbon(N-C) derived from pure PANI. Moreover, the N-HPC electrode demonstrated excellent cycle life, retaining 99% of its initial specific capacitance after 1000 cycles.