N-doped Porous Carbon Spheres Research Articles

Zinc-ion hybrid supercapacitors with hierarchically N-doped porous carbon electrodes and ZnSO4/ZnI2 redox electrolyte exhibit boosted energy density

Zinc-ion hybrid capacitors (ZIHCs) with high energy density is commercial need as energy storing devices, but facile preparation is still a challenge. Herein, we proposed a combined strategy for preparation of ZIHCs with high performance. For this purpose, a nanoemulsion assembly approach with Pluronic F127 as structure-directing agent, 1, 3, 5-trimethylbenzene as pore-expanding agent, polydopamine as carbon and nitrogen source, was used to synthesize hierarchically N-doped porous carbon spheres (N-HNCSs). The optimized sample of N-HNCS-1 exhibited uniform size of 150 nm, hierarchically porous structure, large surface area (705.46 m2 g−1), and N-doping amount of 6.51 %. These properties were beneficial for the transportation of the electrolyte ions resulted in that the N-HNCS-1 electrode displayed superior electrochemical performance with specific capacity of 142 mAh g−1. Furthermore, the Zn//ZnSO4 + ZnI2//N-HNCS-1 ZIHCs achieves an exceptionally high energy density of 347.7 Wh kg−1, which is 3-fold higher than that of Zn//ZnSO4//N-HNCS-1 ZIHCs. To elucidate this outstanding performance, we investigate the mechanisms involved, including Zn2+ deposition/stripping, SO42-/I- adsorption/desorption, Zn4SO4(OH)6⋅0.5 H2O precipitation/dissolution, and redox reactions relating to iodine ions. The incorporation of ZnI2 redox-electrolyte significantly enhanced the energy density by providing prominent pseudocapacitance via the faradaic reaction. Therefore, the high performance of Zn//ZnSO4 + ZnI2//N-HNCS-1 ZIHCs is attributed to the introduction of nitrogen (N) species, advantageous 3D carbonaceous framework, and redox reactions triggered by adding zinc iodide (ZnI2) into the aqueous zinc sulfate (ZnSO4) electrolyte. This groundbreaking research opens up possibilities for the development of high-energy ZIHCs, and advancements in energy storage technology.

In situ growth of highly active Cu-Fe spinel materials on N-doped porous carbon spheres via an adjustable localized microenvironment

Spinel-structured oxides have attracted interest due to their long time stability and good catalytic activity for oxygen reactions. However, what limits the application of spinel-structured oxides in electrocatalysis is the...

Fabricating self-templated and N-doped hierarchical porous carbon spheres via microfluidic strategy for enhanced CO2 capture

N-doped porous biochar is a promising material for CO2 capture due to its easy regeneration and high CO2 selectivity. In this study, a new strategy was proposed to design monodisperse porous carbon spheres by microfluidics system with chitosan in-situ grow ZIF-8, utilizing ZIF-8 as a self-sacrificing template and nitrogen dopant. The mesoporous volume and N content of carbon spheres can be adjusted through the ZIF-8 content in the microfluidic system and carbonization temperature, within 0.01 ∼ 0.48 cm3/g and 3.23 ∼ 19.25%, respectively. The optimum sample (CZ2-900) exhibited superior CO2/N2 selectivity at 40. Adsorption kinetics and diffusion resistance indicated that CO2 adsorption in CZ2-900 is controlled by the process of CO2 diffusion from the surface of the basic site to mesopores. This was the first attempt at using a microfluid chip to grow ZIF-8 in chitosan skeleton and pyrolysis approach to synthesize N-doped porous carbon sphere where both additional template agent and activator are non-used, revealing the potential of microfluidic technology for the precise synthesis of highly selective CO2 capture materials.

Highly Stable and Efficient Oxygen Evolution Electrocatalyst Based on Co Oxides Decorated with Ultrafine Ru Nanoclusters.

Exploring highly active and durable electrocatalysts for oxygen evolution reaction (OER) is significant to achieve efficient anion exchange membrane (AEM) water electrolysis. Herein, hollow Co-based N-doped porous carbon spheres decorated with ultrafine Ru nanoclusters (HS-RuCo/NC) are reported as efficient OER electrocatalysts via the pyrolysis of carboxylate-terminated polystyrene-templated bimetallic zeolite imidazolate frameworks accommodating Ru (III) ions. The unique hollow structure with hierarchically porous characteristics contributes to the electrolyte penetration for fast mass transport and the exposure of more metal sites. Theoretical and experimental studies reveal the synergistic effect between the in situ formed RuO2 and Co3 O4 as another critical factor for the high OER performance, where the coupling of RuO2 with Co3 O4 can optimize the electronic configuration of RuO2 /Co3 O4 heterostructure and decrease the energy barrier during OER. Meanwhile, the presence of Co3 O4 can efficiently suppress the over-oxidation of RuO2 , endowing the catalysts with high stability. As expected, when the resultant HS-RuCo/NCwas integrated into an AEM water electrolyzer, the obtained electrolyzer exhibits a cell voltage of 2.07 V to launch the current density of 1 A cm-2 and excellent long-term stability at 500 mA cm-2 under room temperature in alkaline solution, outperforming the commercial RuO2 -based AEM water electrolyzer (2.19 V).

Facile synthesis of nitrogen-rich porous carbon spheres assisted by NaNH2 as a bifunctional activator and nitrogen source for CO2 capture

It is more important for CO2 adsorbents to simultaneously contain large micropore volume and abundant nitrogen species. In the current work, we proposed a facile approach to synthesis millimeter-sized N-doped porous carbon spheres with developed micropores assisted by NaNH2 as a bifunctional activator and nitrogen source under a mild conditions. The obtained porous carbon spheres show the BET surface areas of 592–2513 m2/g and total N contents of 0.28–5.87 wt% respectively. Abundant micropore volume (pore size < 1 nm) and nitrogen species are mainly created at activation temperature less than 550 °C. The O species formed by preoxidation play an important role in the incorporation of N-containing functional groups that enable the enhancement of CO2 adsorption. The optimal sample of ACSO-Na-550 can achieve high CO2 uptake of 5.83 mmol/g at 0 °C and 1 bar. Furthermore, the ACSO-Na-550 exhibits large CO2/N2 selectivity, excellent recyclability, fast CO2 adsorption rate and high dynamic CO2 uptake due to the synergetic effect of its abundant micropore volume (pore size < 1 nm) and nitrogen species. In addition, the NaNH2 activation possesses the outstanding superiority compared with steam and KOH activation under relatively moderate conditions, endowing porous carbon spheres with promising application for CO2 capture.

FeCo-based mesoporous carbon shells modified N-doped porous carbon spheres for oxygen reduction reaction

FeCo-based non-noble metal electrocatalysts (NNMEs) of FeCo/MCS-NPCS was fabricated by immobilization of hemin on mesoporous carbon shells modified N-doped porous carbon spheres (MCS-NPCS). The obtained FeCo/MCS-NPCS exhibits a half-wave potential (E1/2) of 0.851 ​V versus the reversible hydrogen electrode (vs. RHE) and a limited-diffusion current density (JL) of 5.45 ​mA ​cm−2. In addition, FeCo/MCS-NPCS shows comparable oxygen reduction reaction (ORR) performances to 20 ​wt% Pt/C in terms of E1/2 and JL and better electrochemical properties, including the methanol tolerance and durability in alkaline solution. Such outstanding electrochemical activities of FeCo/MCS-NPCS can be ascribed to Fe and/or Co-based nitrides and carbides as well as N-doped carbon matrixes modified with mesoporous carbon shells. This research introduces a promising path to design and synthesize highly efficient FeCo–N–C electrocatalysts towards ORR.

Boosting Efficient Ammonia Synthesis over Atomically Dispersed Co-Based Catalyst via the Modulation of Geometric and Electronic Structures

Boosting Efficient Ammonia Synthesis over Atomically Dispersed Co-Based Catalyst via the Modulation of Geometric and Electronic Structures

N-doped porous carbon spheres as metal-free electrocatalyst for oxygen reduction reaction

We demonstrate a template-free strategy to synthesize N-doped carbon spheres by pyrolysis of self-assembled UF resin. The NPCS-900 exhibits excellent ORR electrocatalytic performance both in alkaline and acid solution compared to that of Pt/C.

Sustainable Biomass Glucose-Derived Porous Carbon Spheres with High Nitrogen Doping: As a Promising Adsorbent for CO2/CH4/N2 Adsorptive Separation.

Separation of CO2/CH4/N2 is significantly important from the view of environmental protection and energy utilization. In this work, we reported nitrogen (N)-doped porous carbon spheres prepared from sustainable biomass glucose via hydrothermal carbonization, CO2 activation, and urea treatment. The optimal carbon sample exhibited a high CO2 and CH4 capacity, as well as a low N2 uptake, under ambient conditions. The excellent selectivities toward CO2/N2, CO2/CH4, and CH4/N2 binary mixtures were predicted by ideal adsorbed solution theory (IAST) via correlating pure component adsorption isotherms with the Langmuir−Freundlich model. At 25 °C and 1 bar, the adsorption capacities for CO2 and CH4 were 3.03 and 1.3 mmol g−1, respectively, and the IAST predicated selectivities for CO2/N2 (15/85), CO2/CH4 (10/90), and CH4/N2 (30/70) reached 16.48, 7.49, and 3.76, respectively. These results should be attributed to the synergistic effect between suitable microporous structure and desirable N content. This report introduces a simple pathway to obtain N-doped porous carbon spheres to meet the flue gas and energy gas adsorptive separation requirements.

CoS2 embedded graphitic structured N-doped carbon spheres interlinked by rGO as anode materials for high-performance sodium-ion batteries

Much attention has been paid to the Cobalt-based sulfides in recent years due to their high specific capacity and strong catalytic activity in the field of sodium-ion batteries (SIBs). Nevertheless, the poor cycling stability and low rate capability have hindered their practical applications. Herein, an effective strategy for the rational design of CoS2 nanoparticles embedded in the graphitic structured N-doped porous carbon spheres interlinked by the reduced graphene oxide (rGO) nanosheets (rGO-CoS2-GNCSs) is proposed. The interconnected multidimensional nanostructure constructed by CoS2 nanoparticles, graphitic structured N-doped porous carbon spheres and rGO nanosheets can provide a fast transfer pathway for electrons and electrolyte ions, which helps enhance the electric conductivity of the material and facilitate the reaction kinetics in SIBs. Moreover, benefiting from this unique microstructure, the change of the volume during sodiation/desodiation can be effectively alleviated and the stability of the architectural morphology can be enhanced. As a result, the rGO-CoS2-GNCSs used as the anode of SIBs presents an impressive electrochemical performance at a cut-off voltage of 0.4–2.9 V in the electrolyte of 1.0 M NaCF3SO3 in diglyme, delivering a high reversible capacity of 523.9 mAh g−1 at 100 mA g−1 after 150 cycles, an excellent rate capability of 423.3 mAh g−1 at 2 A g−1 and extraordinary long-term cycling stability of 465.9 mAh g−1 at 500 mA g−1 after 600 cycles and 412.2 mAh g−1 at 1 A g−1 after 400 cycles. This study puts forward a promising strategy for the rational design of anode materials for high-efficiency sodium storage by interconnecting transition metal compounds, two-dimensional materials and nanocarbon to form multidimensional nanohybrids.

Enhanced Electrocatalytic Performance through Body Enrichment of Co-Based Bimetallic Nanoparticles In Situ Embedded Porous N-Doped Carbon Spheres.

Extending available body space loading active species and controllably tailoring the d-band center to Fermi level of catalysts are of paramount importance but extremely challenging for the enhancement of electrocatalytic performance. Herein, a melamine-bridged self-construction strategy is proposed to in situ embed Co-based bimetallic nanoparticles in the body of N-doped porous carbon spheres (CoM-e-PNC), and achieve the controllable tailoring of the d-band center position by alloying of Co and another transition metal M (M = Ni, Fe, Mn, and Cu). The enrichment and exposure of the active sites in the body interior of porous carbon spheres, and the best balance between the adsorption of OH species and the desorption of O2 induced by optimizing the d-band center position, collectively enhance the oxygen evolution reaction (OER) performance. Meanwhile, the relationship of d-band center position and OER activity is found to exhibit the volcano curve rule, where the CoNi-e-PNC catalyst shows optimal OER performance with an overpotential of 0.24 V at 10 mA cm-2 in alkaline media, outperforming those of the ever-reported CoNi-based catalysts. Besides, CoNi-e-PNC catalyst also demonstrates high OER stability with slight current decrease after 100 h.

Well-dispersed iron oxide stabilized Fe[sbnd]N4 active sites in porous N-doped carbon spheres as alternative superior catalyst for oxygen reduction

The fabrication of highly active oxygen reduction reaction (ORR) catalysts with strong anti-poisoning and durability at low cost is extremely desirable but still remains a great challenge. Herein, a novel hierarchically structured material of N-doped porous carbon spheres embedded with monodispersed Fe2O3 clusters (Fe2O3/NPCS) is constructed. The composition and microstructure of Fe2O3/NPCS are carefully characterized, and the existed Fe2O3-stabilized FeN4 active sites for ORR are verified. The Fe2O3/NPCS catalyst exhibits a superior ORR activity with a positive half-wave potential of 0.95 V, showing an obvious around 90 mV positive-shift over commercial Pt/C (20 wt%). Additionally, the high ORR catalytic activity is also accompanied by a smaller Tafel slope of 45.3 mV decade−1 than Pt/C, implying a fast kinetics at high potentials. Furthermore, the high-active catalyst also demonstrates an outstanding anti-poisoning capacity and long-term durability. The excellent ORR activites are attributed to the synergistic effect between the rich FeN4 active sites protected by Fe2O3 clusters, the porous structures facilitating electron transport as well as the electrolyte and oxygen diffusion.

Synthesis of Highly Uniform N-Doped Porous Carbon Spheres Derived from Their Phenolic-Resin-Based Analogues for High Performance Supercapacitors

A novel route is developed to synthesize highly uniform N-doped porous carbon spheres (NCS) with a tailorable size ranging from 86 to 205 nm depending on their precursors of phenolic-resin-based analogues. Solid-state NMR and FTIR spectra confirm that the as-synthesized polymer spheres are composed of typical phenolic resin. After activation treatment with KOH, the NCS with a diameter of 86 nm possesses a high surface area of 1462 m2 g–1 coupled with hierarchical (micro and meso) pore structures. Upon these advantages, the prepared carbon sample endows the supercapacitor with high specific capacitance up to 247 F g–1 at 1 A g–1 with excellent rate performance and high cycling stability. Also, the specific energy density is 6.74 Wh kg–1 at a current density of 0.1 A g–1. Therefore, the as-prepared uniform N-doped porous carbon spheres represent a promising candidate for an efficient electrode material.

Toward Bifunctional Overall Water Splitting Electrocatalyst: General Preparation of Transition Metal Phosphide Nanoparticles Decorated N-Doped Porous Carbon Spheres.

It is very important to explore novel synthesis strategies for constructing highly active and inexpensive electrocatalysts for water-splitting. In present work, a novel and efficient coordination-polymerization-pyrolysis (CPP) strategy was developed to prepare cobalt phosphide nanoparticles modified N-doped porous carbon spheres (CoP@NPCSs) hybridsas a powerful catalyst for overall water-splitting (OWS). It can be found that both the carbonization temperatures and the metal contents affect the electrocatalytic performances. As a result, a device assembled with CoP@NPCSs demonstrates low potential (1.643 V @ 10 mA·cm-2) and good stabilization for OWS. Besides, other transition metal phosphides (TMPs)-based materials also can be synthesized by the CPP approach, evidencing the generality of the CPP strategy. Here, we not only constructs a high-efficiency OWS catalyst, but also broadens the synthetic methodology of TMPs from nanoscale.

Novel preparation of N-doped carbon spheres with excellent oxygen reduction reaction catalytic activity

In the present paper, spherical porous N-doped carbon nanomaterials were synthesized using polyaniline nanofiber as nitrogen-carbon precursor through spray drying and high temperature carbonation. In the process of spray drying, polyaniline fibers were entangled to form spherical nanomaterials with pore structures. The average diameter of the carbon spheres prepared by spray drying was about 3 μm. After high temperature carbonation, the diameter shrunk to 2 μm. The catalyst (CSDP-900) which was fabricated by spray drying and high temperature carbonation at 900 °C exhibited a high onset potential and a nearly four-electron pathway for oxygen reduction reaction (ORR) in 0.1M KOH solution as well as stronger methanol tolerance and better long-term durability than commercial Pt/C. This paper provides a novel, easy and scalable method to prepare N-doped porous carbon spheres with excellent ORR catalytic properties.

N-doped and N/Fe-codoped porous carbon spheres derived from tetrazine-based polypyrrole as efficient electrocatalysts for the oxygen reduction reaction

N-doped and N/Fe-codoped carbon materials are currently recognized as the most efficient electrocatalysts for the oxygen reduction reaction (ORR) because of their high catalytic activity, excellent stability, and superior tolerance to fuel. In this work, a novel kind of tetrazine-based polypyrrole spheres (PTPys) is prepared by protonic acid catalyzed Friedel-Crafts polymerization of bis(N-pyrrolyl)-1,2,4,5-tetrazine (TPy) with dimethoxymethane in dichloroethane. The resultant PTPys with a diameter of 100–300 nm are directly pyrolyzed at 900 °C to give N-doped porous carbon spheres (N/Cs-900 electrocatalyst). The N/Fe-codoped porous carbon spheres (Fe/N-Cs-900 electrocatalyst) are then constructed by mixing PTPys with Fe(OAc)2 followed by pyrolysis at 900 °C. The as-synthesized N/Cs-900 and Fe/N-Cs-900 electrocatalysts both have a well-defined spherical architecture together with a relatively high N content, high surface area and porosity. Owing to the synergistic influences, Fe/N-Cs-900 electrocatalyst exhibits excellent ORR activities in both alkaline and acidic electrolytes together with superior poisons tolerance in acidic media, whereas N/Cs-900 electrocatalyst displays ORR activity primarily in alkaline electrolyte. This approach can synthesize heteroatom-doped porous carbon spheres dispensing with the need for any templates, which is of great explored potentiality and utilized value.

Design of Single-Atom Co-N5 Catalytic Site: A Robust Electrocatalyst for CO2 Reduction with Nearly 100% CO Selectivity and Remarkable Stability.

We develop an N-coordination strategy to design a robust CO2 reduction reaction (CO2RR) electrocatalyst with atomically dispersed Co-N5 site anchored on polymer-derived hollow N-doped porous carbon spheres. Our catalyst exhibits high selectivity for CO2RR with CO Faradaic efficiency (FECO) above 90% over a wide potential range from -0.57 to -0.88 V (the FECO exceeded 99% at -0.73 and -0.79 V). The CO current density and FECO remained nearly unchanged after electrolyzing 10 h, revealing remarkable stability. Experiments and density functional theory calculations demonstrate single-atom Co-N5 site is the dominating active center simultaneously for CO2 activation, the rapid formation of key intermediate COOH* as well as the desorption of CO.

Synthesis of Nitrogen-Doped Porous Carbon Spheres with Improved Porosity toward the Electrocatalytic Oxygen Reduction

In this study, a series of activated N-doped porous carbon spheres (ANCSs) have been prepared from biomass as the carbon source to be used as highly active and stable electrocatalysts toward the el...

Highly Enhanced Gas Sorption Capacities of N-Doped Porous Carbon Spheres by Hot NH3 and CO2 Treatments

Highly enhanced CO2 and H2 adsorption properties were achieved with a series of phenolic resin-based carbon spheres (resorcinol–formaldehyde carbon (RFC) and phenol–formaldehyde carbon (PFC)) by carbonization of RF and PF polymer (RFP and PFP) spheres synthesized via a sol–gel reaction and subsequent activation with hot CO2 or NH3 treatment. Monodisperse and size-tunable (100–600 nm) RFC and PFC spheres had intrinsic nitrogen contents (ca. 1.5 wt %), which are attributed to the synthesis conditions that utilized NH3 as a basic catalyst as well as nitrogen precursor. A series of CO2-activated and N-doped RFC and PFC spheres showed almost perfect correlation (R2 = 0.99) between CO2 adsorption capacities and accumulated pore volumes of fine micropores (ultramicropore <1 nm) obtained using the nonlocal density functional theory (NLDFT) model. Interestingly, NH3 activation served not only as an effective method for heteroatom doping (i.e., nitrogen) into the carbon framework but also as an excellent activation...

Large scale production of biomass-derived N-doped porous carbon spheres for oxygen reduction and supercapacitors

The urgent need for sustainable energy development depends on the progress of green technologies, which have steered hot research areas into environmentally benign approaches via inexpensive precursors and abundant resources obtained directly from nature for energy devices such as fuel cells and supercapacitors. By using fermented rice as starting materials, we herein demonstrate a facile, green and scalable approach to synthesize porous N-doped carbon spheres characterised by high specific surface areas (2105.9 m2 g−1) and high porosity (1.14 cm3 g−1), which exhibit not only excellent electrocatalytic activity toward the four-electron oxygen reduction reaction with long-term stability for fuel cells, but also have excellent resistance to crossover effects and CO poisoning superior to that of the commercial Pt/C catalyst. Furthermore, the naturally derived porous N-doped carbon spheres, used as the active electrode materials, present superior performance for capacitors with a capacitance of 219 F g−1 at a high discharge current density of 15 A g−1 and good cycling stability for over 4400 cycles. This work shows a good example for taking advantage of the abundant resources provided by nature, and opening the door for the creation of functional materials with promising applications in high-performance renewable devices related to energy conversion and storage.