Co-doped Carbon Nanosheets Research Articles

Preparation of Hierarchical Porous Fe/N Codoped Carbon Nanosheets as Oxygen Reduction Reaction Electrocatalysts for the Zinc-Air Battery

Preparation of Hierarchical Porous Fe/N Codoped Carbon Nanosheets as Oxygen Reduction Reaction Electrocatalysts for the Zinc-Air Battery

Edge‑nitrogen/sulfur co-doping boost high potassium ion storage of carbon nanosheet anode materials

Potassium-ion batteries (PIBs) have garnered considerable attention as a potential alternative to lithium-ion batteries. However, the larger radius of K+ poses challenges, including slow kinetic processes and significant volume changes, which adversely affect the rate performance and cycling stability of electrode materials. Herein, N, S co-doped carbon nanosheets (xNS-HC) are synthesized as anode materials of PIBs by carbonization of citric acid and CH₄N₂S precursors in LiCl/KCl molten salts. Of these, 5NS-HC possesses a high N content of 20.19 at.% with 90.90 % of edge N-species and a S content of 2.53 at.%. The 5NS-HC material exhibits a high specific K+ storage capacity of 368.2 mAh g−1 at 0.1 A g−1, superior rate capability (106.1 mAh g−1 at 10 A g−1), and long-term cycling stability (205.8 mAh g−1 after 2800 cycles at 1 A g−1). In-depth analysis via in-situ XPS and DFT calculations reveals that the active sites doped with edge-N/S exhibit a profound affinity towards K+, thus contributing to the outstanding electrochemical K+ storage performance observed in 5NS-HC. The full cell of K0.4Mn0.9Li0.1O2·0.33H2O||5NS-HC exhibits a high specific capacity of 141.2 mAh g−1, supporting a high energy density of 147.1 Wh kg−1. These compelling results illustrate that edge-N/S co-doping can significantly enhance the K+ storage of carbon anode materials.

Boosting Zn-air battery performance: Fe single-atom anchored on F, N co-doped carbon nanosheets for efficient oxygen reduction

Sluggish oxygen reduction reaction (ORR) kinetics limit the development of metal-air batteries and fuel cells, hindering overall energy conversion efficiency. Therefore, significant research has focused on cost-effective, highly active, and exceptionally stable non-precious metal ORR electrocatalysts. This study presents the synthesis of a nanohybrid material called Fe SAs/FN-CNs. It is made up of single iron atoms embedded in ultrathin porous carbon nanosheets that are co-doped with F and N. The synthesis process involves an easy one-step pyrolysis technique without additional post-treatment. The Fe SAs/FN-CNs material is designed to function as an effective zinc-air battery ORR electrocatalyst. Based on their distinctive components and structure, the optimal Fe SAs/FN-CNs exhibit outstanding catalytic efficiency and long-lasting performance in the alkaline ORR. They have an onset potential (Eonset) of 0.95 V, a half-wave potential (E0.5) of 0.85 V, a kinetic current density (JK) of 20.49 mA cm−2 at 0.8 V, and a diffusion-limited current (Jd) of 6.2 mA cm−2. In addition, a Zn-air battery made using homemade Fe SAs/FN-CNs demonstrated a power density of 197 mW cm−2, a specific capacitance of 813.5 mAh g−1, and exceptional stability. It outperformed the commercial Pt/C by operating continuously for over 147 hours at 10 mA/cm² (discharge-charge). The Fe SAs/FN-CNs nanohybrid electrocatalyst shows great potential as an electrocatalyst for various metal-air batteries.

Facile one-pot synthesis of Bi2S3 nanorod @ N, S co-doped carbon composite for high performance lithium ion batteries

Bismuth sulfide is favoured in lithium ion batteries due to its high specific capacity of 625 mAh/g. However, the Bi2S3 anode faces severe volume expansion problems during the lithium intercalation process, resulting in continuous electrode fragmentation and rapid degradation of lithium storage performance. In this study, Bi2S3 nanorod@N, S co-doped carbon composite prepared by a simple sintering method was used as the anode material for lithium ion batteries. 1D Bi2S3 nanorods with a length of 1 μm and a diameter of 50 nm were loaded in situ on 2D N, S co-doped carbon nanosheets. This unique structure can not only alleviate the volume change of bismuth sulfide, but also effectively shorten the diffusion distance of lithium ions, thereby improving the cycling stability and rate capability at the same time. The discharge capacity of Bi2S3@N, SC remained at 583.4 mAh g –1 after 400 cycles at 0.5 A g–1. Even at a high current density of 2 A/g, the discharge capacity of Bi2S3@N, SC still reached 374.3 mAh g –1. This simple method also can be extended to the preparation of other metal sulfide composites.

Cobalt/nitrogen co-doped carbon nanosheets from coal-based graphene quantum dots boosted oxygen reduction

We report on cobalt/nitrogen co-doped carbon nanosheets (Co/NCNs) as a highly efficient electrocatalyst for the oxygen reduction reaction (ORR). The Co/NCNs were synthesized through pyrolysis at 900 °C using coal-based graphene quantum dots that contain nitrogen as a source of both carbon and nitrogen, NaCl as a template, and trace amounts of cobalt salt as a metal source. The Co/NCNs-0.1 exhibited ORR activity that was equivalent to that of Pt/C, with a half-wave potential of 0.85 V and a limiting current density of 4.9 mA cm−2. Furthermore, the zinc-air battery incorporating Co/NCNs-0.1 demonstrated an open circuit voltage of 1.423 V, a maximum power density of 149 mW cm−2, and a specific capacity of 806.5 mAh g−1 at a current density of 20 mA cm−2. The results of density functional theory calculations indicate that metal Co, when protected by graphitic-N-doped carbon, holds a greater negative charge and exhibits a lower energy barrier compared to other types of nitrogen species. This property contributes to the catalytic activity of the ORR.

3D Co-doped carbon nanosheets as high-performance electrodes for Li-S batteries

3D petal-shaped Cobalt-doped carbon nanosheets (PCoCNS) were synthesized as excellent sulfur hosts for lithium-sulfur (Li-S) batteries. Co doping enhanced the affinity of the carbon surface for lithium polysulfides (LiPSs), inhibiting the shuttle effect. The electrocatalytic effect of the PCoCNS electrode exhibited enhanced polysulfide conversion kinetics, thereby promoting Li2S formation. Owing to the above advantages, the PCoCNS cathode exhibited satisfactory reversibility of 841 mAh/g with a high capacity retention of 91 %. Additionally, it displayed high coulombic efficiency (CE) values exceeding 97 % over 100 cycles at a current rate of 0.5C. Furthermore, the electrode demonstrated low polarization and exhibited an excellent rate performance, delivering a capacity of 575 mAh/g at the high rate of 3C. This study synthesized a promising sulfur cathode for enhancing the electrochemical performance of Li-S batteries.

In situ construction of sea urchin-like structural NiCo-LDH coated cobalt‑nitrogen co-doped carbon as high-performance electrode for supercapacitor

Nickel‑cobalt layered double hydroxide (NiCo-LDH) has received much attention in the field of supercapacitor electrodes due to its multiple oxidation states and good electrochemical activity. However, NiCo-LDH often suffers from structural instability and low conductivity in practical applications. In this study, sea urchin-like structural NiCo-LDH coated cobalt‑nitrogen co-doped carbon (NiCo-LDH@Co-NC-x) electrode materials were prepared by in situ growth of NiCo-LDH on the surface of cobalt‑nitrogen co-doped carbon nanosheets (Co-NC) using a one-step hydrothermal method. The results show that the NiCo-LDH@Co-NC-2 electrode material exhibits excellent electrochemical performance, its specific capacitance is up to 1909 F g−1 at a current density of 1 A g−1, and capacitance retention of 69.5 % (only 26.2 % for NiCo-LDH) can be achieved after 10,000 cycles at a current density of 10 A g−1. This is because the abundant and uniformly distributed Co nanoparticles on Co-NC provide nucleation sites for the in-situ growth of NiCo-LDH, effectively improving the interface binding between Co-NC and NiCo-LDH, enhancing the structural stability of NiCo-LDH, and ensuring highly efficient electron transport throughout the NiCo-LDH@Co-NC-2 electrode. An asymmetric supercapacitor (NiCo-LDH@Co-NC-2//AC) was further assembled with NiCo-LDH@Co-NC-2 and activated carbon (AC) as positive and negative electrodes, respectively, achieving an energy density as high as 36.8 Wh kg−1 at a power density of 750 W kg−1. These findings suggest that the NiCo-LDH@Co-NC-2 composite can be a promising candidate for high-performance supercapacitor electrode.

Fluorine and Nitrogen Codoped Carbon Nanosheets In Situ Loaded CoFe2O4 Particles as High-Performance Anode Materials for Sodium Ion Hybrid Capacitors

Fluorine and Nitrogen Codoped Carbon Nanosheets In Situ Loaded CoFe₂O₄ Particles as High-Performance Anode Materials for Sodium Ion Hybrid Capacitors

Elucidating the effects of nitrogen and phosphorus co-doped carbon on complex spinel NiFe2O4 towards oxygen reduction reaction in alkaline media

The study presents for the first time complex spinel NiFe2O4 nanoparticles supported on nitrogen and phosphorus co-doped carbon nanosheets (NPCNS) prepared using sol gel and the carbonization of graphitic carbon nitride with lecithin as a highly active and durable electrocatalyst for oxygen reduction reaction. The physicochemical properties of complex spinel NiFe2O4 on NPCNS and subsequent nanomaterials were investigated using techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrochemical activity of the electrocatalysts was evaluated using hydrodynamic linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. The electrocatalytic performance of the NiFe2O4/NPCNS nanohybrid electrocatalyst is dominated by the 4e− transfer mechanism, with an onset potential of 0.92 V vs. RHE, which is closer to that of the Pt/C, and a current density of 7.81 mA/cm2 that far exceeds that of the Pt/C. The nanohybrid demonstrated the best stability after 14 400 s, outstanding durability after 521 cycles, and the best ability to oxidize methanol and remove CO from its active sites during CO tolerance studies. This improved catalytic activity can be attributed to small nanoparticle sizes of the unique complex spinel nickel ferrite structure, N-Fe/Ni coordination of nanocomposite, high dispersion, substantial ECSA of 47.03 mF/cm2, and synergy caused by strong metal-support and electronic coupling interactions.

3D porous N/S co-doped carbon nanosheets derived from ionic liquids as efficient electrocatalysts for direct methanol fuel cells

The efficiency of direct methanol fuel cells (DMFC) is determined by the oxygen reduction reaction (ORR) of the cathode and the methanol oxidation reaction (MOR) of the anode. As a consequence, current research concentrates on the creation of efficient and stable electrocatalysts to expedite the slow kinetics of ORR and MOR. In this work, three-dimensional porous network non-metallic nitrogen/sulfur co-doped carbon nanosheets (N/SC) as cathode oxygen reduction electrocatalysts were synthesized using protonated histidine ionic liquids as the precursor, g-C3N4 as the porogen and in-situ nitrogen dopant. Among them, the N/SC800 possesses a high specific surface area with a layered porous structure, and the doping components are equally distributed and rich in nitrogen. For ORR, the N/SC800 had an onset potential (0.985 V) and a half-wave potential (0.841 V), and its durability and methanol tolerance were overmatched to commercial Pt/C. Additionally, Pt nanoparticles supported on N/SC800 (Pt@N/SC800) were prepared by the ethylene glycol reduction and used in the methanol oxidation, outperforming Pt/C in methanol oxidation activity and stability. This work provides a strategy for the synthesis of highly efficient ionic liquid-based bifunctional electrocatalysts.

Tungsten phosphide on nitrogen and phosphorus-doped carbon as a functional membrane coating enabling robust lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) hold great potential as future energy storage technology, but their widespread application is hampered by the slow polysulfide conversion kinetics and the sulfur loss during cycling. In this study, we detail a one-step approach to growing tungsten phosphide (WP) nanoparticles on the surface of nitrogen and phosphorus co-doped carbon nanosheets (WP@NPC). We further demonstrate that this material provides outstanding performance as a multifunctional separator in LSBs, enabling higher sulfur utilization and exceptional rate performance. These excellent properties are associated with the abundance of lithium polysulfide (LiPS) adsorption and catalytic conversion sites and rapid ion transport capabilities. Experimental data and density functional theory calculations demonstrate tungsten to have a sulfophilic character while nitrogen and phosphorus provide lithiophilic sites that prevent the loss of LiPSs. Furthermore, WP regulates the LiPS catalytic conversion, accelerating the Li-S redox kinetics. As a result, LSBs containing a polypropylene separator coated with a WP@NPC layer show capacities close to 1500 mAh/g at 0.1C and coulombic efficiencies above 99.5 % at 3C. Batteries with high sulfur loading, 4.9 mg cm−2, are further produced to validate their superior cycling stability. Overall, this work demonstrates the use of multifunctional separators as an effective strategy to promote LSB performance.

Coupling harmful algae derived nitrogen and sulfur co-doped carbon nanosheets with CeO2 to enhance the photocatalytic degradation of isothiazolinone biocide

Removing the algae from water bodies is an effective treatment toward the worldwide frequently occurred harmful algae blooms (HAB), but processing the salvaged algae waste without secondary pollution places another burden on the economy and environment. Herein, a green hydrothermal process without any chemical addition was developed to resource the HAB algae (Microcystis sp.) into autogenous nitrogen and sulfur co-doped carbon nanosheet materials C–CNS and W–CNS, whose alga precursors were collected from pure culture and a wild bloom pond, respectively. After coupling with CeO2, the obtained optimal C–CNS/CeO2 and W–CNS/CeO2 composites photocatalytically degraded 95.4% and 88.2% of the marine pollutant 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in 90 min, significantly higher than that of pure CeO2 (63.15%). DCOIT degradation on CNS/CeO2 was further conducted under different conditions, including pH value, coexisting cations and anions, and artificial seawater. Although different influences were observed, the removal efficiencies were all above 76%. Along with the ascertained good stability and reusability in five consecutive runs, the great potential of CNS/CeO2 for practical application was validated. UV–vis DRS showed the increased light absorption of CNS/CeO2 in comparison to pure CeO2. PL spectra and photoelectrochemical measurements suggested the lowered charge transfer resistance and thereby inhibited charge recombination of CNS/CeO2. Meanwhile, trapping experiments and electron paramagnetic resonance (EPR) detection verified the primary roles of hydroxyl radical (OH) and superoxide radical (O2−) in DCOIT degradation, as well as their notably augmented generation by CNS. Consequently, a mechanism of CNS enhanced photocatalytic degradation of DCOIT was proposed. The intermediates involved in the reaction were identified by LC-QTOF-MS, giving rise to a deduced degradation pathway for DCOIT. This study offers a new approach for resourceful utilization of the notorious HAB algae waste. Besides that, photocatalytic degradation has been explored as an effective measure to remove DCOIT from the ocean.

Controllable sulfur redox multi-pathway reactions regulated by metal-free electrocatalysts anchored with LiS3* radicals

Regulating sulfur redox kinetics is an effective strategy for addressing the critical issues in lithium-sulfur batteries and improving their comprehensive performance. However, the sluggish and complex sulfur reduction reaction (SRR) kinetics can seriously deteriorate the electrochemical performance of lithium-sulfur batteries, hindering a clear comprehension of the electrocatalytic mechanism and presenting challenges for targeted design. Hence, it is crucial to elucidate the SRR mechanism and further refine the catalytic principle. In this study, the SRR mechanism and the pivotal role of radicals are comprehensively explored using ultrathin nitrogen-oxygen co-doped carbon nanosheets (UN/O-CNS) as an electrocatalytic model, combining density functional theory calculations with experimental techniques, such as X-ray absorption near-edge structure spectroscopy. The abundant N-O active sites of UN/O-CNS can synergistically anchor LiS3* radicals, facilitating efficient multi-pathway sulfur conversion. Additionally, UN/O-CNS can capture and catalyze polysulfides while also bi-directionally catalyzing Li2S. The S@UN/O-CNS cells ultimately demonstrate ultra-long cycling performance and high load capacity. The successful operation in pouch cells validates the practical effectiveness of UN/O-CNS. Overall, this study offers novel insights into the complexity and potential pathways of sulfur redox reaction, providing new perspectives for exploring the catalytic mechanism of cost-effective metal-free electrocatalysts.

Preparation and Lithium-Ion Capacitance Performance of Nitrogen and Sulfur Co-Doped Carbon Nanosheets with Limited Space via the Vermiculite Template Method.

Nitrogen and sulfur co-doped graphene-like carbon nanosheets (CNSs) with a two-dimensional structure are prepared by using methylene blue as a carbon source and expanded vermiculite as a template. After static negative pressure adsorption, high-temperature calcination, and etching in a vacuum oven, they are embedded in the limited space of the vermiculite template. The addition of an appropriate number of mixed elements can improve the performance of a battery. Via scanning electron microscopy, it is found that the prepared nitrogen-sulfur-co-doped carbon nanosheets exhibit a thin yarn shape. The XPS results show that there are four elements of C, N, O, and S in the carbon materials (CNS-600, CNS-700, CNS-800, CNS-900) prepared at different temperatures, and the N atom content shows a gradually decreasing trend. It is mainly doped into a graphene-like network in four ways (graphite nitrogen, pyridine nitrogen, pyrrole nitrogen, and pyridine nitrogen oxide), while the S element shows an increasing trend, mainly in the form of thiophene S and sulfur, which is covalently linked to oxygen. The results show that CNS-700 has a discharge-specific capacity of 460 mAh/g at a current density of 0.1 A/g, and it can still maintain a specific capacity of 200 mAh/g at a current density of 2 A/g. The assembled lithium-ion capacitor has excellent energy density and power density, with a maximum power density of 20,000 W/kg.

Preparation of Co[sbnd]N co-doped carbon nanosheets electrocatalyst for efficient oxygen reduction reaction in zinc-air battery

It is very vital that there be a high-activity and serviceable catalyst for the oxygen reduction reaction (ORR) in the Zn-air Battery. Herein, utilizing g-C3N4 as a self-sacrifice template and Cobalt-His framework as the precursor, a simple strategy was developed to synthesize Co/N co-doped carbon nanosheets (CoNC 800) as a metal electrocatalyst for ORR. Due to the Co/N co-doped CoNX site and large specific surface area, the acquired materials show a preeminent ORR catalytic activity with an initial potential (~0.96 V) and half-wave potential (E1/2) of 0.85 V (vs. RHE) in an alkaline medium. Most importantly, the material has superior long-term stability and methanol tolerance than Pt/C. Furthermore, we assembled the Zn-air battery employing catalyst as an air cathode catalyst, demonstrating maximum power densities of 144 mWcm−2, a specific capacity of 821.50 Wh·kg−1, and charge/discharge cycle stability of more than 140 h. The nanosheet structure electrocatalysts derived from the Cobalt-His framework and g-C3N4 provide an innovative and instructive approach to the design of diverse nanomaterials.

γ-Fe2O3 decorating N,S co-doped carbon nanosheets as a cathode electrocatalyst for different-scenario fuel cells

The decoration of γ-Fe2O3 nanoparticles onto N,S co-doped carbon nanosheets enhances their catalytic activity for the oxygen reduction reaction (ORR) in both neutral and alkaline environments, making them a promising candidate for applications in various fuel cell scenarios.

A bottom-up puzzle strategy for P/B co-doped carbon nanosheets as efficient oxygen reaction electrocatalysts

Preparing metal-free and non-N-doped carbon-based electrocatalysts via pyrolysis encounters a significant challenge of low controllability for microstructure modulation and limited electrocatalytic activity. Herein, a bottom-up puzzle strategy is proposed to fabricate a series of phosphorus and boron co-doped carbon (P-BC) nanosheets. These P-BC nanosheets manifest diverse morphologies and distinct heteroatom doping levels, achieved through the innovative utilization of four similar P onium salts featuring varying benzene ring arrangements, coupled with a fixed B onium salt. Among them, the flat 4P-BC nanosheets with abundant P/B heteroatoms exhibit the optimal oxygen reduction reaction (ORR) performance (E1/2 = 0.79 V, jL = 5.77 mA cm−2), and the assembled zinc-air battery displays a large power density (163 mW cm−2) and excellent long-term durability (450 cycles), which is attributed to the high specific surface area, enhanced defects or disorder, and ample P/B-doping induced active sites for electrochemical reaction. The assembly mechanism of functional units in solution and their intricate evolution at high temperature are elucidated for various P-BC nanosheets. This work elaborates the influence of precursors functional units on the resulting microstructure attributes and active sites properties, providing a novel avenue for the rational design and optimization of metal-free and heteroatom-doped carbon electrocatalysts.

N and P co-doped graphene-like carbon nanosheet as metal-free catalyst for selective oxidation of methacrolein to methacrylic acid: High methacrylic acid selectivity

Methacrylic acid (MAA) is an important chemical intermediate. In this study, a kind of nitrogen-phosphorus co-doped graphene-like carbon nanosheet catalysts have been prepared by co-pyrolysis of starch and (NH4)2HPO4, which have high specific surface area (1057.55 m2g−1) and excellent catalytic performance (35% of MAL conversion and 90% of MAA selectivity) for the selective oxidation of methacrolein to methacrylic acid. The graphite nitrogen provides new active sites for adsorption and activation of O2 which can accelerate the reaction. P in carbon skeleton can enrich the electron on the surface of carbon catalyst and turn the electrophilic groups to nucleophilic groups which can increase the MAA selectivity. This study provides a convenient and fast method to prepare efficient nitrogen and phosphorus co-doped carbon catalysts for the selective oxidation of methacrolein to methacrylic acid.

Preparation of B/N co-doped carbon nanosheets and their electrochemical performance in Zn-ion redox capacitors

The low energy density for conventional supercapacitors has limited their further application in a large scale. To enhance the energy density of supercapacitor, a novel redox Zn-ion supercapacitor is fabricated by using B, N codoped carbon nanosheets as cathode material and hydroquinone as redox electrolyte. The B, N co-doping is found to be beneficial for the enhanced electrochemical performance, and the introduced redox electrolyte has increased the capacitance of supercapacitor greatly. The B, N codoped carbon nanosheets shows a capacity of 168 mAhg−1 in the hydroquinone based redox electrolyte at 2 Ag−1, nearly 2 times as that (83 mAhg−1) in conventional Zn-ion electrolyte. Density functional calculation shows B, N- dual doping can increase the adsorption capability of carbon toward hydroquinone. This work shows that the combination of cathode material modification and redox electrolyte can enhance Zn-ion hybrid supercapacitor.

2D-COFs-derived heteroatom-doped carbon nanosheets as high-efficiency all-solid frustrated lewis pair metal-free hydrogenation catalyst

Metal-free catalysts without metal active sites participating in the reactions have obtained growing attraction under the drive of the economic and environmental problems. Here, 2D-COFs-drived B/N co-doped carbon nanosheets as metal-free catalyst was synthesized by Schiff-based coupling reaction and self-templated carbonization. It shows excellent catalytic performance in nitro compound hydrogenation reaction as all-solid FLP catalyst in H2 system (100 % conversion of nitrobenzene and 99.89 % selectivity to aniline) without any metal active species in the catalyst. This result is the most promising compared to the previous literatures. In the study, the high crystallinity of precursor 2D-COFs is imperative for catalytic stability, and the function of B atoms modification and the B-N synergism were investigated carefully. The formation of B-N bond as a fixed all-solid FLP active center was verified, and it also indicates that B atoms introduction can make the carbon nanosheets orderly and enhance the strength and amount of the acid and base sites. The catalytic mechanism of hydrogen activation was also studied by combining the characterization results and density functional theory (DFT) calculations. The results show that the B atoms doping and defects formation efficiently accelerate the charges aggregation between B-N bonds to form Lewis pairs, and the TS searching calculations shows the significant decrease of H2 dissociation barrier energy and the reaction energy, demonstrating the effectiveness of N and B co-doping strategy. This work is very promising and the metal-free catalyst is the potential alternative to traditional metal catalysts.