Co-doped Carbon Nanospheres Research Articles

Preparation of Multi-element Doped Carbon Nanospheres with Core-shell Structure Derived from Polystyrene as Lubricating Additives for Improving Tribological Behavior

In this study, the multi-element doped carbon nanospheres with core-shell structure (N,P,S-PCNs) have been successfully synthesized through the carbonization of hyper-cross-linked polystyrene nanospheres (HPSs) encapsulated with poly(cyclotriphosphazene-co-4,4’-sulfonyldiphenol) (PZS). The phosphonitrilic chloride trimer can in-situ assemble on HPSs surface, forming a poly(phosphonitrilic chloride trimer) film via sulfonyldiphenol as cross-linking agent to obtain HPSs@PZS. Subsequently, the HPSs@PZS undergoes high-temperature calcination under N2 atmosphere, and PZS with a well-preserved encapsulation capability efficiently incorporated N, P and S into carbon nanospheres to gain multi-element (N,P,S) co-doped carbon nanospheres (N,P,S-PCNs) with core-shell structure. The prepared N,P,S-PCNs exhibit exceptional dispersibility and stability as lubricant additives, effectively mitigating friction (reduced to 0.106) and wear (decreased by 84.0 %). The lubrication performance of N,P,S-PCNs is exceptional due to the nanospheres' remarkable ability to enter the gaps between friction pairs and form a deposition film on the surfaces. Moreover, the nanospheres can undergo a chemical reaction with the matrix surface, resulting in the formation of a chemical protective film. The composite protective film (deposition film and chemical protective film) significantly enhances the lubricants' ability to reduce friction and resist wear.

Iron-nitrogen co-doped carbon nanospheres prepared by template-free melting salt-assisted pyrolysis as efficient and durable oxygen reduction catalysts

It is necessary to seek oxygen reduction reactions (ORRs) electrocatalyst that can replace commercial Pt/C for new energy conversion devices. Herein, we used molten salt-assisted pyrolysis to successfully convert small nitrogen-containing carbon molecules directly into iron-nitrogen codoped carbon nanospheres (Fe–N–Cs) without the need for external templates. Molten salts provide a solvo-like environment for the high-temperature pyrolysis of small carbon molecules and bulk oxides. Small molecules containing nitrogen and carbon are subjected to spatial domain-limiting effect, reducing volatilization in the calcination processes. Besides, the strong polarity provided by molten salts can not only dissolve bulk oxides but also prevent free metal atoms from gathering again to form particles or clusters. The synthesized Fe–N–Cs exhibit excellent ORR activity. The half wave potential (E1/2, 0.67 V vs. RHE) in acidic solution is almost equivalent to Pt/C. Furthermore, Fe–N–Cs have the ability to prevent methanol poisoning and its stability is strong.

In-situ pyrolysis synthesis of multi-element (F, N, S) co-doped porous carbon nanospheres as lubricating additives with improved tribological behaviors

Herein, hyper-crosslinked polystyrene nanospheres (HPSs) were synthesized via emulsion polymerization and Friedel-Crafts reaction utilizing styrene as the primary raw material. The multielement (F, N, S) co-doped carbon nanospheres with enriching microporous structures were synthesized using ionic liquid ([EMIM]NTf2) assisted carbonization of HPSs under 400 °C. The fabricated carbon nanospheres exhibit excellent dispersion stability as well as remarkable anti-friction and anti-wear properties. In comparison to pure 500SN, the friction coefficient of the multielement (F, N, S) co-doped carbon nanospheres is reduced to 0.108, resulting in 81.9 % reduction in wear volume. Furthermore, the friction coefficient shows minimal fluctuation under different frequency and temperature conditions, which is significantly lower by 21.4 % and 31.6 % respectively compared to 500SN, while exhibiting an improved carrying capacity of up to 550 N. Through Raman spectroscopy, XPS, as well as FIB-TEM analysis, the result revealed that tribochemical reactions occur between the active elements within the nanospheres and the friction pairs leading to the formation of the composite protective film (40–70 nm) composed mainly of the deposition film and the frictional chemical protective film, achieving superior frictional performance.

Back interface management by multifunctional composite carbon nanospheres electrode for efficient and stable HTL-free carbon-based perovskite solar cells

The fabrication of a carbon electrode with high hole extraction and simultaneous the function of improving back interface properties is a critical and efficient strategy to enhance the performance of carbon-based perovskite solar cells (C–PSCs) free of hole transport layer (HTL). Herein, a compound of MoS2 and MoP in situ composite N, P co-doped carbon nanospheres (MoS2–MoP/NPC) is constructed as an efficient carbon electrode for HTL-free PSCs. The excellent p-type characteristic of MoS2, the high conductivity of MoP and the co-doping of N, P heteroatoms endow the composite carbon nanospheres with high hole mobility and conductivity and a down-shifted work function, which significantly promotes the extraction and transportation of holes and decreases energy loss. Meanwhile, the N, P and S components of the MoS2–MoP/NPC nanospheres exert a passivation effect on the surface free positive ions defects of the perovskite film, resulting in a remarkable reduction in non-radiative recombination at back interface. As a result, the HTL-free CsPbBr3 PSCs without any encapsulation based on MoS2–MoP/NPC electrode achieve a champion power conversion efficiency of 10.13% with a significant open-circuit voltage of 1.638 V and excellent long-term stability after storage at 85% RH, 85 °C in air for 30 days. This work provides a new perspective for designing multifunctional carbon electrode materials that holistically optimize the back interface to improve the efficiency and stability of HTL-free C–PSCs.

Mn, N co-doped carbon nanospheres for efficient capture of uranium (VI) via capacitive deionization

Heteroatom doping, involving the introduction of atoms with distinct electronegativity into carbon materials, has emerged as an effective approach to optimize their charge distribution. In this study, we designed a strategy to synthesize in-situ Mn, N co-doped carbon nanospheres (Mn-NC) through the polycondensation of 2,6-diaminopyridine and formaldehyde in synchronization with Mn2+ chelation to form Mn-polytriazine precursor, followed by calcination to form carbonaceous solid. Then Mn-NC was fabricated into a capacitive deionization (CDI) electrode for the selective removal of uranium ions (U (VI)), which is commonly found in radioactive water. Interestingly, Mn-NC exhibited good selectivity for UO22+ capture with a demonstrated adsorption capacity of approximately 194 mg/g @1.8 V. The systematic analysis of the adsorption mechanism of UO22+ revealed that N dopants within Mn-NC can coordinate with the U (VI) ions, thereby facilitating the removal process. Our study presents a straightforward and convenient strategy for removing UO22+ ions by harnessing the coordination effect, eliminating the requirement for pore size control.

In-situ formation of nitrogen doped microporous carbon nanospheres derived from polystyrene as lubricant additives for anti-wear and friction reduction

This study presents a nitrogen-doped microporous carbon nanospheres (N@MCNs) prepared by a facile polymerization–carbonization process using low-cost styrene. The N element in situ introduces polystyrene (PS) nanospheres via emulsion polymerization of styrene with cyanuric chloride as crosslinking agent, and then carbonization obtains N@MCNs. The as-prepared carbon nanospheres possess the complete spherical structure and adjustable nitrogen amount by controlling the relative proportion of tetrachloromethane and cyanuric chloride. The friction performance of N@MCNs as lubricating oil additives was surveyed utilizing the friction experiment of ball-disc structure. The results showed that N@MCNs exhibit superb reduction performance of friction and wear. When the addition of N@MCNs was 0.06 wt%, the friction coefficient of PAO-10 decreased from 0.188 to 0.105, and the wear volume reduced by 94.4%. The width and depth of wear marks of N@MCNs decreased by 49.2% and 94.5%, respectively. The carrying capacity of load was rocketed from 100 to 400 N concurrently. Through the analysis of the lubrication mechanism, the result manifested that the prepared N@MCNs enter clearance of the friction pair, transform the sliding friction into the mixed friction of sliding and rolling, and repair the contact surface through the repair effect. Furthermore, the tribochemical reaction between nanoparticles and friction pairs forms a protective film containing nitride and metal oxides, which can avert direct contact with the matrix and improve the tribological properties. This experiment showed that nitrogen-doped polystyrene-based carbon nanospheres prepared by in-situ doping are the promising materials for wear resistance and reducing friction. This preparing method can be ulteriorly expanded to multi-element co-permeable materials. Nitrogen and boron co-doped carbon nanospheres (B,N@MCNs) were prepared by mixed carbonization of N-enriched PS and boric acid, and exhibited high load carrying capacity and good tribological properties.

Spherical porous iron-nitrogen-carbon nanozymes derived from a tannin coordination framework for the preparation of L-DOPA by emulating tyrosine hydroxylase.

L-3,4-Dihydroxyphenylalanine (L-DOPA) is widely used in Parkinson's disease treatment and is therefore in high demand. Development of an efficient method for the production of L-DOPA is urgently required. Nanozymes emulating tyrosine hydroxylase have attracted enormous attention for biomimetic synthesis of L-DOPA, but suffered from heterogeneity. Herein, a spherical porous iron-nitrogen-carbon nanozyme was developed for production of L-DOPA. Tannic acid chelated with ferrous ions to form a tannin-iron coordination framework as a carbon precursor. Iron and nitrogen co-doped carbon nanospheres were assembled via an evaporation-induced self-assembly process using urea as a nitrogen source, F127 as a soft template, and formaldehyde as a crosslinker. The nanozyme was obtained after carbonization and acid etching. The nanozyme possessed a dispersive iron atom anchored in the Fe-N coordination structure as an active site to mimic the active center of tyrosine hydroxylase. The material showed spherical morphology, uniform size, high specific surface area, a mesoporous structure and easy magnetic separation. The structural properties could promote the density and accessibility of active sites and facilitate mass transport and electron transfer. The nanozyme exhibited high activity to catalyze the hydroxylation of tyrosine to L-DOPA as tyrosine hydroxylase in the presence of ascorbic acid and hydrogen peroxide. The titer of DOPA reached 1.2 mM. The nanozyme showed good reusability and comparable enzyme kinetics to tyrosine hydroxylase with a Michaelis-Menten constant of 2.3 mM. The major active species was the hydroxyl radical. Biomimetic simulation of tyrosine hydroxylase using a nanozyme with a fine structure provided a new route for the efficient production of L-DOPA.

Boron and nitrogen co-doped porous carbon nanospheres for oxidative dehydrogenation of ethane to ethylene

Boron and nitrogen co-doped carbon nanospheres (BXCN) were fabricated using graphitic carbon nitride (g-C3N4) as the precursor and the nitrogen source, and boric acid as the boron source. They featured high specific surface area and porous structure. Besides, the doping of B brought improved chemical and thermal stability of the material. They were further used as catalysts for the oxidative dehydrogenation of ethane (ODHE) for the first time. The BXCN demonstrated higher conversion of ethane and higher selectivity towards ethylene, compared with other carbon catalysts such as carbon nanotubes reported in literature. An ethane conversion of 15.8% with a selectivity of 56.0% towards ethylene were achieved on B0·1CN at a reaction temperature of 525 °C. The B0·1CN showed an excellent stability within 7 h ODHE test at 450 °C. This work offers a new strategy of using heteroatoms co-doped carbon-based catalysts with improved activity for ODHE under lower temperatures.

Boron and nitrogen co-doped carbon nanospheres for supercapacitor electrode with excellent specific capacitance

At present, carbon materials derived from biomass precursors have many limitations in the field of energy storage. In this study, boron and nitrogen (B/N) co-doped carbon nanospheres are successfully prepared by emulsion crosslinking method using chitosan and boric acid as raw materials. After carbonization at high temperature, the carbon nanospheres can be facilely prepared with controllable particle size, showing excellent structural stability and sphericity. In addition, the heteroatoms co-doping endows the carbon nanospheres with large specific surface area, high graphitization degree and excellent electrochemical performance. Applying the carbon nanospheres for supercapacitors, the specific capacitance can reach up to 336.7 F g−1 at a current density of 1 A g−1. Even after 10,000 cycles, the Coulomb efficiency and specific capacitance still remain at 98.61% and 96.8%, respectively, demonstrating the great promise of B/N co-doped carbon nanospheres for the state-of-the-art supercapacitor electrodes applications.

Nitrogen-doped porous carbon nanospheres derived from hyper-crosslinked polystyrene as lubricant additives for friction and wear reduction

A novel porous carbon nanospheres doped with nitrogen (N@MCNs) was prepared from hyper-crosslinked polystyrene nanospheres with melamine-assisted carbonization. The N element are found to be evenly distributed in the entire carbon nanospheres, the as-prepared N@MCNs are effective in reducing friction and wear as an additive, which was attributed to the robust protective films that occurred because of tribo-chemical reactions induced via N@MCNs. The formation of protective films comprising nitrides and metal oxides can improve anti-wear and friction reduction performance of 500SN. The friction coefficient of N@MCNs was reduced from 0.413 to 0.11, the wear volume was reduced by 83.5%. The experiment provides a reliable and effective approach to preparing co-doped carbon nanospheres from inexpensive polystyrene for friction and wear reduction.

Uniform lithium nucleation/deposition regulated by N/S co-doped carbon nanospheres towards ultra-stable lithium metal anodes

N and S co-doped mesoporous carbon nanospheres show strong affinity towards lithium ions, which dramatically reduce the lithium nucleation barrier and improve the stability of SEI layer, boosting a dendrite-free lithium metal anode.

Controllable lithium deposition behavior hollow of N, O co-doped carbon nanospheres for practical lithium metal batteries

Metallic Li is of great significance for high energy Li-based batteries due to its high specific capacity, low electrochemical potential, and low density. However, host-less Li deposition and dendritic growth are the main bottlenecks in Li-based batteries’ practical application. We demonstrate a hollow N, O co-doped carbon nanosphere (NOCS) as a current collector for Li metal anode in this work. It can alleviate the volume effect and delay the generation of Li dendrite and induce the uniform deposition of Li on the NOCS electrode and improve Coulombic efficiency (CE). Li/NOCS half cells deliver a higher CE and longer cycle life, and symmetrical cells exhibit lower voltage hysteresis and more stable cyclic performance. DFT calculation confirmed that N-doping and O-doping improve the affinity between N/O-doped carbon sites with Li. Besides, we use finite Li as the anode to prepare the Li@NOCS||LiFePO4 full cells to evaluate the possibility of practical application. The Li@NOCS||LiFePO4 full cells have excellent cycling and rate performance compared to Li@Cu|| LiFePO4 full cells.

NHighly N/O co-doped carbon nanospheres for symmetric supercapacitors application with high specific energy

Carbon nanospheres (CSs) with high synthetic yield, large specific surface area (SBET), high heteroatom dopant and hierarchical porosity exhibits unique advantages in supercapacitor applications, yet integrating all these merits into one material is still challengeable. Herein, we developed a template-free CuCl2-activation strategy to high-yield preparation of highly N/O co-doped porous CSs derived from a quinone-amine polymer precursor. It is found that the mild activating effect of CuCl2 not only can retain the initial nanosphere structure of the precursor, but also can enable the target CSs to achieve high-level N/O dopants (14.9/10.6 at.%), large SBET (2957.8 m2 g−1), and ultrahigh carbon yield (~60%). Benefiting from these merits, the optimal CS-CuCl2-800 sample exhibits a delightful capacitance of 273.9 F g–1 at 0.5 A g–1, excellent cyclic performance (capacitance retention, ~96.5%) during 10,000 charging/discharging cycles at 2 A g–1, and a moderate energy output of 8.0 Wh kg–1 in 6 M KOH electrolyte. When used ion-liquid electrolyte, the energy density of the device is further boosted to 80.3 Wh kg–1, and the corresponding solid-state supercapacitors based on the ionic liquid gel electrolyte still maintain an high energy output of 71.3 Wh kg–1, which is superior to many reported solid-state supercapacitors. Therefore, the facile activation strategy together with tunable properties, high carbon yield, and excellent electrochemical performance indicate promising application prospects in the large-scale fabrication of commercial porous carbons.

Revealing the dependence of active site configuration of N doped and N, S-co-doped carbon nanospheres on six-membered heterocyclic precursors for oxygen reduction reaction

Elucidating the correlation of the polymer precursors and active sites formation of multi-heteroatom doped based carbon for oxygen reduction reaction (ORR) is essential to develop molecular-level design of highly efficient metal-free carbon catalysts. To achieve this goal, herein, two series of N doped and N, S co-doped carbon nanospheres were synthesized via pyrolysis of self-polymerized compounds of three analogous precursors of 2,6-Diaminopyridine, 4, 6-Diaminopyrimidine and 1,3-Diaminobenzene as nitrogen source initiated by hydrogen peroxide and ammonium persulfate as sulfer source respectively. The results demonstrate that nitrogen atoms in the six-membered rings of three precursors play a critical role on the formation of N-doping types and synergistic effects of N and S dopants in their derived carbon nanoshperes for ORR. Among the three precursors, 2,6-Diaminopyrimidine prefers to form the Pyridinic N doped carbon, resulting in the highest activity for ORR in N doped nanospheres, in contrast, 2,6-Diaminopyridine facilitates the formation of more content of Graphitic-N dopant, which has stronger synergy with thiophenic-S dopant in carbon matrix than that of Pyridinic N dopants. This unique characteristic endows 2,6-Diaminopyrimidine derived N, S co-doped nanospheres with excellent ORR activity of higher half-wave potential of 0.87 V vs. RHE in 0.1 M KOH and Zn-Air battery power output performance than that of the same loading of commercial Pt/C catalyst. Revealing the dependence of specific active sites determined by precursors with very similar molecular structures in the work will shed light on the precise design strategy based on the precursors-selecting guidance for the development of advanced multi-heteroatom doped carbon ORR catalysts.

Nitrogen-Phosphorus Codoped Carbon Nanospheres as Lubricant Additives for Antiwear and Friction Reduction

Nitrogen and phosphorus doping have been proven to be effective strategies for improving the tribological properties of carbon-based materials when used as lubricating oil additives. Herein, an efficient strategy is demonstrated for the preparation of nitrogen and phosphorus codoped organic carbon nanospheres (denote as N, P@CN) via a template-free interfacial copolymerization combined with ammonium hypophosphite-assisted carbonization. The N and P are found to be homogeneously distributed through the entire carbon shell. The tribological properties of as-prepared materials as base oil additives under different test conditions were evaluated. The as-prepared N, P@CNs exhibit good dispersibility and stability in base oil due to the presence of many organic functional groups. Moreover, they are considered to be thermal stable at elevated temperatures, and the existing robust structure makes them favorable as lubricant additives. The experiment results show that the friction reduction and wear resistance abilities of N, P@CNs were superior to that of pure base oil, because N, P@CNs can induce tribo-chemical reactions to form a protective film on the interfaces due to the combined effect of nitrogen and phosphorus. The obtained N, P@CNs could increase the load carrying capacity of base oil from 250 N to 1050 N. The coefficient of friction can be reduced to 0.08, and the corresponding wear volume loss can be decreased by 90%. These findings open up a possibility to prepare environmentally friendly lubricant additives, such as carbon nanospheres doped with other elements, to achieve excellent antiwear and friction-reducing characteristics.

A selective etching approach to pore structure control of polymeric precursors: creating hierarchical porous N, P co-doped carbon nanospheres for semi-solid-state supercapacitors

A selective etching strategy based on a dynamic imine–amine exchange was developed to construct porous carbon nanospheres for supercapacitors.

Rechargeable Zinc-Air Battery with Ultrahigh Power Density Based on Uniform N, Co Codoped Carbon Nanospheres.

Highly efficient catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key to the commercialization of rechargeable zinc-air batteries (ZABs). In this work, a catalyst with uniform nanospherical morphology was prepared from cobalt nitrate, acetylacetone, and hydrazine hydrate. The final catalyst possesses high ORR and OER performances, with a half-wave potential of 0.911 V [vs reversible hydrogen electrode (RHE)] for ORR and a low potential of 1.57 V (vs RHE) at 10 mA cm-2 for OER in 0.1 M KOH solution. Specially, a ZAB based on the catalyst demonstrates an ultrahigh power density of 479.1 mW cm-2, as well as excellent stability, and potential in practical applications.

Ultrahigh energy density of a N, O codoped carbon nanosphere based all-solid-state symmetric supercapacitor

A novel quinone–amine route is developed to fabricate N, O codoped carbon nanospheres for an all-solid-state supercapacitor with an ultrahigh energy density.

Preparation of high-capacitance N,S co-doped carbon nanospheres with hierarchical pores as supercapacitors

The N,S co-doped carbon nanospheres with/without hierarchical pores (N,S-HPCNs/N,S-CNs) are prepared by the pyrolysis of polypyrrole and (NH4)2S2O8 with/without F127 as the pore-foaming agent in flowing N2. The results show that the combination of the hierarchical pores and N,S co-doping improves the electrochemical properties of carbon materials. As a result, the specific capacitance of N,S-HPCNs is as high as 416 F g−1 at a current density of 0.2 A g−1, which is much higher than that of N,S-CNs (138 F g−1). At a current density of 10 A g−1, the specific capacitance of 313 F g−1 for N,S-HPCNs is obtained, which keeps a capacitance retention of 75.2%, while the N,S-CNs has only the capacitance retention of 44.2%. After 5000 cycles, the retention ratio of N,S-HPCNs as high as 95.8% is obtained and the columbic efficiency of N,S-HPCNs is close to 100%. The symmetric supercapacitor device assembled using N,S-HPCNs exhibited a high energy density of 18.1 Wh kg−1 at a power density of 100 W kg−1. The exhibited excellent electrochemical performances of N,S-HPCNs are attributed to a high content of doped heteroatoms N and S and the hierarchical pore structure.

Double-Shelled Phosphorus and Nitrogen Codoped Carbon Nanospheres as Efficient Polysulfide Mediator for High-Performance Lithium-Sulfur Batteries.

Lithium–sulfur batteries are regarded as very promising energy storage devices due to their high energy density, low cost, and environmental friendliness; however, their insulating properties and the instability of sulfur‐based electrodes impede the practical applications of Li–S batteries. Here, a versatile strategy to synthesize double‐shelled nitrogen and phosphorus codoped carbon spheres (NPDSCS) as an efficient sulfur host for Li–S batteries is reported. With strong trapping, good affinity, high adsorption for polysulfides, and the bifunctional catalyzing for sulfur redox processes, the developed NPDSCS cathodes with a high S loading of 72.4% exhibit large specific discharge capacity of 1326 mAh g−1 at 0.1C, high Coulombic efficiency, good rate capability, and excellent cycling performance with a reversible capacity of 814 mAh g−1 at 1C after 500 cycles.