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(a) Schematic illustration of nitrogen plasma doping process with possible N configurations (left side); a high-resolution TEM image (right side) and selected area electron diffraction (inset) of the N-doped graphene indicate that the intrinsic layered structure and original honeycomb-like atomic structure were preserved during the plasma process. Adapted with permission from ref. 108. Copyright (2011) American Chemical Society. (b) Scheme of the photochemical chlorination process (left); optical images of a single-layer graphene sheet before and after photochemical chlorination, respectively (right, blue color); D band mapping (l ex = 514.5 nm) of CVD-grown graphene film after patterned photochlorination (right, green colour). Adapted with permission from ref. 113. Copyright (2011) American Chemical Society.
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Heteroatom doping can endow graphene with various new or improved electromagnetic, physicochemical, optical, and structural properties. This greatly extends the arsenal of graphene materials and their potential for a spectrum of applications. Considering the latest developments, we comprehensively and critically discuss the syntheses, properties an...
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... et al. developed a photochemical method for homogeneous and patternable Cl-doping on graphene (Fig. 8b). 113 Under the xenon lamp radiation (maximum power density of 1.4 W cm À2 ), chlorine molecules split into highly reactive radicals, which, in turn, covalently conjugate to the basal carbon atoms of graphene. Homogeneous doping (B8 at%) was verified by Raman mapping. Interestingly, doped-graphene becomes more transparent due to the widening of the graphene ...
Context 2
... Other approaches. With a short reaction time and low power consumption, plasma treatment is an effective method for heteroatom doping. Jeong et al. successfully achieved N doping in N 2 plasma (500 W in power, 14 Torr of N 2 gas) using H 2 -plasma treated GO as the starting material (Fig. 8a). 108 A large number of defect sites produced from the H 2 plasma reduction process improve the effectiveness of N doping on the graphene basal plane. N-doping level and bond- ing configurations can be tuned by varying the aging time in N 2 plasma. The maximum N content of 2.51 at% was obtained after a 3 min plasma treatment. During the plasma process, pyrrolic N that preferably forms at the defect sites continuously increases, while graphitic N decreases and pyridinic N remains steady. NH 3 plasma is more reactive than N 2 plasma. 109,110 However, the level of N-doping attainable by plasma treat- ment is generally less as compared to other doping methods. Plasma technique is particularly effective for halogen atom doping because halogen atoms are highly reactive. Wu et al. demonstrated plasma-assisted chlorine-doping on CVD graphene at a low power, without the generation of considerable defects. 111 A Cl coverage of 8.5 at% and conductance enhancement due to the p-doping effect were observed. By tuning the plasma conditions (reaction time, dc bias, vacuum level, etc.), Zhang et al. achieved extremely high Cl-doping of 45.3 at% (close to C 2 Cl) on CVD graphene. 112 The C/Cl ratio and bonding states (C-Cl interaction through ionic bonding, covalent bonding, and defect creation) are sensitive to the DC bias ...
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... Incorporating polar atoms into the as-prepared carbon-based materials is generally done by a post-treatment ( Figure 3A). 63,64 According to specific operation process, the posttreatment approach commonly includes direct heattreatment under a precursor containing polar atoms ( Figure 3B) 56 and wet chemical treatment with a precursor containing polar atoms followed by hydrothermal carbonization 63,65 and/or high-temperature annealing ( Figure 3C). 66,67 The precursors containing polar atoms applied in post-treatment process generally comprise of ammonia (NH 3 ), 56 chitosan, 60 ionic liquids, 16 melamine, 68 urea, 69 phytic acid, 60 N-allylthiourea, 11 NaH 2 PO 4 , 70 diammonium hydrogen phosphate (DHP), 71 MgSO 4 , 58 H 3 BO 3 , 61 BCl 3 , 72 fluorine gas (F 2 ), 55 hydrofluoric acid (HF), 73 and so on. ...
The electrolyte‐wettability at electrode material/electrolyte interface is a critical factor that governs the fundamental mechanisms of electrochemical reaction efficiency and kinetics of electrode materials in practical electrochemical energy storage. Therefore, the design and construction of electrode material surfaces with improved electrolyte‐wettability has been demonstrated to be important to optimize electrochemical energy storage performance of electrode material. Here, we comprehensively summarize advanced strategies and key progresses in surface chemical modification for enhancing electrolyte‐wettability of electrode materials, including polar atom doping by post treatment, introducing functional groups, grafting molecular brushes, and surface coating by in situ reaction. Specifically, the basic principles, characteristics, and challenges of these surface chemical strategies for improving electrolyte‐wettability of electrode materials are discussed in detail. Finally, the potential research directions regarding the surface chemical strategies and advanced characterization techniques for electrolyte‐wettability in the future are provided. This review not only insights into the surface chemical strategies for improving electrolyte‐wettability of electrode materials, but also provides strategic guidance for the electrolyte‐wettability modification and optimization of electrode materials in pursuing high‐performance electrochemical energy storage devices.
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... In addition, the larger and smaller radii of the F atom (64 pm) and Cl atom (99 pm) compared with the C atom (77 pm) could stretch the C-C bond length to 1.57-1.58 Å (with F conjugation) and 1.89 Å (with Cl conjugation) (Wang et al. 2014), respectively, thereby introducing more vacancy and edge defects. The stretching of graphene layers via Cl species loading was confirmed by Arvas et al. (2022), and the thickness of graphene layers was adjusted from 1.13 to 2.96 nm by Cl regulation. ...
Highly active catalysts with salt and acid/alkali resistance are desired in peroxymonosulfate (PMS) activation processes and marine environment applications. F- and Cl-doped graphene (F-GN and Cl-GN) were prepared via electronegative and atom radius adjustment for tetracycline hydrochloride (TCH) pollution removal to satisfy these requirements. The introduction of special F and Cl functionalities into graphene exhibits superior electron transfer properties for PMS activation, considering the experimental and density functional theory (DFT) calculation results. The TCH degradation efficiency reached up to 80% under various pH and salt disturbance conditions with F-GN and Cl-GN. Cl-GN exhibited an activity superior to F-GN due to the higher electron polarization effect of C atoms adjacent to Cl atoms. The presence of more positive charged C sites in Cl-GN (around Cl doping) is more favorable for PMS attachment and sequence radical generation than F-GN. In addition, the main active species functionalized during reaction included ·OH and SO4⁻·, and the stability of F-GN and Cl-GN was confirmed to be over 60% by recycle test. Final research results provide an effective strategy for designing and preparing PMS activators resistant to salt, acid, and alkali, thereby expanding their application potential.
... [9,10] In the above reference, the doping of heteroatom(s) like N, P, S, and B into graphene is considered to be an important strategy to improve its electrical conductivity, surface area, creation of more defects/active sites, enhance wettability and pseudocapacitance. [11,12] For example, N (3.04) having larger electronegativity than C (2.55) may create polarization in the carbon network, thereby, affecting graphene's electronic and optical properties. Moreover, its electron-rich nature results in distinct bonding configurations (pyridinic, pyrrolic, and graphitic) in Ndoped graphene. ...
... In the case of S doping, C─S bond formation causes low polarization due to similar electronegativity of S (2.58) and C (2.55). [11,12] Whereas, the P-doping causes more distortion in carbon structure to that of N-doping, forming a pyramidal bond configuration with three carbon atoms, thus transforming it from sp 2 hybridized to sp 3 hybridized carbon resulting in P overhanging from the graphene plane. It forms the P─C bond, which has a bigger bond length than that of the C─C bond, and also develops a polarity opposite to that of the C─N bond, as the electronegativity of P (2.19) is lower as compared to C (2.55). ...
... Thus, a variation in the content of P doping is envisaged to further modify these structural characteristics and needs to be explored to enhance the electrochemical features. [11][12][13] Concerning electrolytes, the safety issues like flammability, poor conductivity, and toxicity associated with the commercially used aqueous (like LITFSI (bis(trifluoromethylsulfonyl)amine lithium salt)) and nonaqueous organic electrolytes [14,15,18] can be avoided by employing certain aqueous water-in-salt (WIS) like neutral electrolyte(s) for their characteristic high ionic concentrations, superb thermal stability in wide temperature range, lower viscosity, higher conductivity, and volatility, besides being cheaper. [16][17][18][19] In this reference, NaClO 4 -like neutral electrolyte having fairly high solubility (17 mol kg −1 ), lower cost, nonflammability, high ionic conductivity, high tolerance against moisture, low viscosity, and stability in wide temperature ranges (−31 to 100°C), makes it a potential electrolyte for both batteries and supercapacitors. ...
This manuscript reports a one‐pot synthesis of ternary heteroatoms (N/S/P) co‐doped reduced graphene oxide as an electrode material by simultaneous reduction/doping of/into graphene oxide employing eco‐friendly natural molecule(s) (thiamine monophosphate (TM) and thiamine pyrophosphate (TP)) under mild heating (≤60 °C) and near‐neutral pH (≤8) conditions. It produces N, S, P co‐doped rGO‐TM and N, S, P co‐doped rGO‐TP nanohybrids displaying a well‐connected porous microstructure with significantly doped atomic(%) ‐N (10.0%), S (4.1%), P (0.1%) and N (6.7%), S (2.0%), and P (0.5%), respectively. The symmetric supercapacitor designed using N, S, P‐rGO‐TM‐10 in water‐in‐salt 17 m NaClO4 electrolyte exhibits stable cell voltage of 3.0 V, superb gravimetric energy density (areal energy density) of 47.9 Wh kg⁻¹@522.8 W g⁻¹ (0.2363 Wh cm⁻²@ 2.5 W cm⁻²); the excellent cyclic stability (88.8 %) and Coulombic efficiency (99.2%) even after 20 000 cycles. Their energy storage capability is corroborated by the illumination of 109 white LEDs upon lighting a single SSC for 50 s each, driving a motor to run a fan, and forming the tandem device by joining three such cells in series.
... Numerous studies report strategies for synthesizing chemically doped graphene, enabling the design and improvement of chemical applications of graphenebased materials and devices [10][11][12][13][14][15][16][17]. Among various approaches, the atomistic introduction of nitrogen into graphene is a powerful and widespread technique for tailoring the physicochemical properties of graphene by increasing the charge populations of the hybridization network [18][19][20][21]. In particular, the thermal treatment of graphene oxide (GO) with a nitrogen-containing reducing agent such as ammonia, hydrazine, or melamine effectively produces nitrogen-doped reduced graphene oxide (NRGO). ...
Nitrogen-doped graphene has been increasingly utilized in a variety of energy-related applications, serving as a catalyst or support material for fuel cells, and as an anode material for lithium-ion batteries, among others. The thermal reduction of graphene oxide (GO) in nitrogenous sources to incorporate nitrogen, producing nitrogen-doped reduced graphene oxide (NRGO), is the most favored method. Controlling atomic configurations of nitrogen-doped sites is the key factor for tailoring the physico-chemical properties of NRGO, but major challenges remain in identifying detailed atomic arrangements at nitrogen binding sites on highly defective and chemically functionalized GO surfaces. In this paper, we present atomistic-scale modeling of the nitrogen doping process of GO with different types of vacancy defects. Molecular dynamics simulations using a reactive force field indicate that the edge carbon atoms on defect sites are the dominant initiation location for nitrogen doping. Further, first-principles calculations using density functional theory present energetically favorable chemical transition pathways for nitrogen doping. The significance of this work lies in providing important chemical insights for the effective control of the desired properties of NRGO by suggesting a detailed mechanism of the nitrogen doping process of GO.
... Doping is achieved by annealing the material with the appropriate dopant agent sources after synthesis, which is a universal post-synthesis method. With this method, a better understanding of doped graphene materials, different levels and configurations of doping, as well as synergy effects from co-dopants, is examined [185]. By thermal annealing, high-concentration boron can be doped into the GNPs. ...
... These properties were exploited in a variety of technological applications across various fields, including linear magnetoresistance [10], magnetic storage [11], energy storage [12], chemical engineering [13], semiconductors [14], biology [15,16], solar cells [17], environmental sciences [18] and field-effect transistors [19]. Moreover, although graphene is a diamagnetic material [20], magnetic behavior can be induced in processed graphene through various experimental methods, including the introduction of nitrogen-substituted molecules [21], replacement [22], hydrogenation [23], adsorption [24] and heteroatom doping [25]. It has also been demonstrated that the presence of defects, such as vacancies and impurity atoms, can lead to magnetism in graphene [26][27][28]. ...
... We also note that the system shows three saturation values at zero temperature under the effect of crystal field Δ 2 /|J 3 |, namely M=0. 25 . It is also important to note that for Δ 2 /|J 3 | = − 4.00, −3.00, −2.00, −1.00 and −0.25, M peaks are reached at low temperatures. ...
Using the mean-field approximation based on the Gibbs-Bogoliubov inequality for the free energy, we conducted an investigation into the magnetic properties and hysteresis behavior of a graphene Ising bilayer, where the top and bottom layers are occupied by spins σ = 3/2 and S = 5/2, respectively. The effects of exchange interactions, crystal fields, external magnetic field and temperature on the
total magnetization, partial magnetizations of each layer, total magnetic susceptibility, blocking temperature and hysteresis loops of the system were thoroughly analyzed. The variations of the blocking temperature as a function of various parameters in the system's Hamiltonian were presented. Furthermore, we demonstrated the existence of multiple hysteresis loop behaviors under specific
physical conditions.
... 23−26 The covalent interaction involves heteroatoms substituted or covalently bonded to the carbon atoms of graphene; however, it essentially alters the electronic structure of graphene. 27 On the other hand, noncovalent interactions, such as molecular deposition and substrate effects, preserve the electronic structure of graphene. 28 In addition, noncovalent chemical doping can deterministically modulate the Fermi level of graphene, which allows us to probe the correlation between band alignment, charge transfer, and the GERS enhancement without ambiguity. ...
... It is thought that the presence of higher oxygen groups, in addition to the better dispersion of nanoparticles, leads to a relative loss of conductivity and stability of GQDs, which doping with nitrogen solves these problems. The remarkable electronegativity difference between N (3.04) and C (2.55) causes polarity in the carbon network and improves the electronic, magnetic, and optical properties of these types of materials 40,41 . Doped nitrogen results in electrocatalytic activity improvement of the metal nanoparticles by providing the necessary electron withdrawal 42 . ...
... Recently, our group synthesized Pd(0) supported on nitrogen-doped graphene quantum dots modified cellulose as an efficient catalyst for the green reduction of nitroaromatics with excellent properties 41 . In continuation, herein, we used PdNPs supported on N-GQD (PdNPs@N-GQD) as an electrode modifier for the preparation of sensitive and selective electrochemical sensor for AA detection. ...
To precise screening concentration of ascorbic acid (AA), a novel electrochemical sensor was prepared using palladium nanoparticles decorated on nitrogen-doped graphene quantum dot modified glassy carbon electrode (PdNPs@N-GQD/GCE). For this purpose, nitrogen doped GQD nanoparticles (N-GQD) were synthesized from a citric acid condensation reaction in the presence of ethylenediamine and subsequently modified by palladium nanoparticles (PdNPs). The electrochemical behavior of AA was investigated, in which the oxidation peak appeared at 0 V related to the AA oxidation. Considering the synergistic effect of Pd nanoparticles as an active electrocatalyst, and N-GQD as an electron transfer accelerator and electrocatalytic activity improving agent, PdNPs@N-GQD hybrid materials showed excellent activity in the direct oxidation of AA. In the optimal conditions, the voltammetric response was linear in the range from 30 to 700 nM and the detection limit was calculated to be 23 nM. The validity and the efficiency of the proposed sensor were successfully tested and confirmed by measuring AA in real samples of chewing tablets, and fruit juice.
... Pyridine nitrogen and pyrrole nitrogen correspond to N atoms distributed at the edge of graphene and defects, both of which bond with two C atoms to form a five-membered ring. [38,39] From Table S3, it can be seen that the pyridine nitrogen content of SNGA-0, SNGA-300, SNGA-500 and SNGA-700 samples is 7.6 %, 12.8 %, 30.2 % and 48.0 %, respectively, and the content of pyrrole nitrogen is 59.5 %, 61.9 %, 47.2 % and 25.4 %, respectively. Which indicates that with the increase of calcination temperature, pyridine nitrogen content shows a gradual increase trend and pyrrole nitrogen shows a gradual decreasing trend. ...
... Figure S5(a) displayed the EIS spectra of GA-500, SNGA-5, SNGA-15, SNGA-25, and SNGA-35 electrodes. Among them, SNGA-15 exhibited a smaller diameter semicircle and more inclined linear slope compared to GA-500, which was attributed to the electron transfer of N doping destroying the π-electron inertia of the adjacent C atom, [38] thus exciting the activity of the neighboring positively charged Sp 2 À C and the S atom's electronic configuration of the C atom regulating effect. [59,60] For better quantitative analysis of the testing data, an ideal equivalent circuit was used to fit the impedance spectrum, and the fitting results were shown in the Figure S5(b). ...
The nitrogen and sulfur co‐doped graphene aerogel (SNGA) was synthesized by a one‐pot hydrothermal route using graphene oxide as the starting material and thiourea as the S and N source. The obtained SNGA with a three‐dimensionally hierarchical structure, providing more available pathways for the transport of lithium ions. The existing form of S and N was regulated by changing the calcination temperature and thiourea doping amount. The results revealed that high temperature could decompose −SOX− functional groups and promote the transformation of C−S−C to C−S, ensuring the cyclic stability of electrode materials, and increasing the thiourea dosage amount introduced more pyridine nitrogen, improving the multiplicative performance of electrode materials. Benefiting from the synergistic effect of sulfur and nitrogen atoms, the prepared SNGA showed superior rate capability (107.8 mAh g⁻¹ at 5 A g⁻¹), twice more than that of GA (52.8 mAh g⁻¹), and excellent stability (232.1 mAh g⁻¹ at 1 A g⁻¹ after 300 cycles), 1.85 times more than that of GA (125.6 mAh g⁻¹). The present study provides a detailed report on thiourea as a dopant to provide a sufficient basis for SNGA and a theoretical guide for further modifying.
... Traditional doping techniques suffer from uncontrollable tear (C-C bond breaking) and very slow repair (C-N or C-B bond formation) mechanisms. In contrast, MW doping involves controlled tear and prompt repair which enables MW tremendous potential for performing heteroatom doping efficiently, promptly, and most importantly graphitically [38][39][40] . ...
... eV) with an insignificant peak at 287.2 eV which confirms minimal oxygen functionality. Upon 15,[29][30][31][32]39,40 . The doping level as well as graphitic % is the best in microwave N720 (theoretical limit~33% sp 2 incorporation achieved) and B850. ...
Insufficient carrier concentration and lack of room temperature ferromagnetism in pristine graphene limit its dream applications in electronic and spintronic chips. While theoretical calculations have revealed that graphitic ultradoping can turn graphene into semiconducting and room temperature ferromagnetic, the exotic set of thermodynamic conditions needed for doping result in defects and functionalities in graphene which end up giving significant electronic scattering. We report our discovery of microwave ultradoping of graphene with N > 30%, B ~ 19%, and co-doping to form BCN phases (B 5 C 73 N 22 , B 8 C 76 N 16 , and B 10 C 77 N 13 ). An unprecedented level of graphitic doping ~95% enhances carrier concentration up to ~9.2 × 10 12 cm ⁻² , keeping high electronic mobility ~9688 cm ² V ⁻¹ s ⁻¹ intact, demonstrated by field effect transistor measurements. Room temperature ferromagnetic character with magnetization ~4.18 emug ⁻¹ is reported and is consistent with our DFT band structure calculations. This breakthrough research on tunable graphitic ultradoping of 2D materials opens new avenues for emerging multi-functional technological applications.
