Abstract:Nitrogen-doped graphene (NG) has attracted increasing attention because its properties are significantly different to pristine graphene, making it useful for various applications in physics, chemistry, biology, and materials science. However, the NGs that can currently be fabricated using most experimental methods always have low N concentrations and a mixture of N dopants, which limits the desirable physical and chemical properties. In this work, first principles calculations combined with the local particle-… Show more
“…The above formation energy was calculated at a relatively N ‐deficient environment, which accords well with the operating conditions of our experiment. The formation energy of N ‐doped carbon structures on different chemical conditions ( μ N ) is further shown (Figure S20A, Supporting Information), where N‐6 could be dominant under N ‐rich conditions, in good agreement with the other results 57,58 . N ‐doped structures are found to be stabilized further with an N‐Q to substitute N‐5 (Figure S20B, Supporting Information).…”
Nitrogen doping has readily emerged as an efficient solution to boost potassium‐ion storage of carbonaceous materials. Nevertheless, the capacity and lifespan enhancement of derived electrodes is still plagued by the incompetent in coordinating the dopant configurations. In the realm of emerging potassium‐ion hybrid capacitor (PIHC) device, dictating nitrogen doping to enhance pseudocapacitive behavior and improve K+ diffusion kinetics of carbonaceous anodes is scarcely demonstrated. Herein, we report the design of hierarchical N‐doped carbon nanopolyhedron@nanosheet composite via a salt‐confined synthetic strategy with tunable doping configurations toward advanced PIHC anode. A harmonized edge‐ to graphitic‐nitrogen ratio in such dual‐carbon materials enables outstanding rate capability (130 mAh g−1 at 10.0 A g−1) and cyclic performance (with a capacity retention of 80% after 2000 cycles at 5.0 A g−1) in half‐cell tests. As expected, the thus‐assembled PIHC full device with a working voltage of 4.2 V presents a high energy/power density (146 Wh kg−1/8000 W kg−1) and favorable cyclicability. This work is anticipated to offer an innovative insight into the coordination of nitrogen doping configurations in heteroatom‐doped carbon anode targeting high‐performance PIHC applications.
“…The above formation energy was calculated at a relatively N ‐deficient environment, which accords well with the operating conditions of our experiment. The formation energy of N ‐doped carbon structures on different chemical conditions ( μ N ) is further shown (Figure S20A, Supporting Information), where N‐6 could be dominant under N ‐rich conditions, in good agreement with the other results 57,58 . N ‐doped structures are found to be stabilized further with an N‐Q to substitute N‐5 (Figure S20B, Supporting Information).…”
Nitrogen doping has readily emerged as an efficient solution to boost potassium‐ion storage of carbonaceous materials. Nevertheless, the capacity and lifespan enhancement of derived electrodes is still plagued by the incompetent in coordinating the dopant configurations. In the realm of emerging potassium‐ion hybrid capacitor (PIHC) device, dictating nitrogen doping to enhance pseudocapacitive behavior and improve K+ diffusion kinetics of carbonaceous anodes is scarcely demonstrated. Herein, we report the design of hierarchical N‐doped carbon nanopolyhedron@nanosheet composite via a salt‐confined synthetic strategy with tunable doping configurations toward advanced PIHC anode. A harmonized edge‐ to graphitic‐nitrogen ratio in such dual‐carbon materials enables outstanding rate capability (130 mAh g−1 at 10.0 A g−1) and cyclic performance (with a capacity retention of 80% after 2000 cycles at 5.0 A g−1) in half‐cell tests. As expected, the thus‐assembled PIHC full device with a working voltage of 4.2 V presents a high energy/power density (146 Wh kg−1/8000 W kg−1) and favorable cyclicability. This work is anticipated to offer an innovative insight into the coordination of nitrogen doping configurations in heteroatom‐doped carbon anode targeting high‐performance PIHC applications.
“…It is worth noting that N-substituted W-diamanes have no magnetism, while the CNCN phase has a tiny magnetization [21]. The magnetism occurs in 2D carbons when the 2D carbons are structurally distorted or defected, for example, hydrogenated graphene, 2D carbon nitrides that are porous structure, diamond surface with Pandey's reconstruction [24,[33][34][35][36][37]. The latter needs HSE06 for calculation in order to obtain magnetism [24], while magnetism can be acquired using PBE for the former two [33,34].…”
Section: Electronic Property and Bondingmentioning
One type of two-dimensional diamonds that are derived from [111] direction, so-called diamane, has been previously shown to be stabilized by N-substitution, where the passivation of dangling bonds is no longer needed. In the present work, we theoretically demonstrated that another type of two-dimensional diamonds derived from [110] direction exhibiting a washboard conformation can also be stabilized by N-substitution. Three structural models of washboard-like carbon nitrides with compositions of C6N2, C5N3, and C4N4 are studied together with the fully hydrogenated washboard-like diamane (C8H4). The result shows that the band gap of this type structure is only open the dangling bonds that are entirely diminished through N-substitution. By increasing the N content, the C11 and C22 are softer and the C33 is stiffer where their bulk modulus are in the same order, which is approximately 550 GPa. When comparing with the hydrogenated phase, the N-substituted phases have higher elastic constants and bulk modulus, suggesting that they are possibly harder than the fully hydrogenated diamane.
“…However, it is not a good presentation because different types of GCNs are being compared. Bu et al 19 shows that the formation energy of N-doped graphene and GCNs with pyridinic N increase similarly with amount of N concentration up to 0.25%. The former starts increasing higher if N concentration is more than 0.3%.…”
Section: Resultsmentioning
confidence: 98%
“…Figure 6 c shows that the formation energy of the ordered solid solutions is below zero with respect to those of TRI-N and TRI-C indicating that the connector C and N atoms are likely to be chemically ordered at low temperature in thermodynamic equilibrium. The transition temperature between order-disordered phase that helps to verify a structure found in the experiment, for instance, HEP/TRI-C/N 56 , hence needs to be investigated 19 , but it is beyond the scope of this work. Figure 6 ( a ) Some order phases of TRI-C/N alloy are illustrated for a demonstration.…”
Section: Resultsmentioning
confidence: 99%
“…One method used to create void defects in graphene is by doping N atoms where the voids are surrounded by N atoms, then N-doped graphene becomes magnetic 15 , 16 . Although, high doping, void, and passivation concentrations lead to phase instability limiting amounts of spin density in graphene 17 – 19 .…”
We use the first principle calculation to investigate the intrinsic magnetism of graphitic carbon nitrides (GCNs). By preserving three-fold symmetry, the GCN building blocks have been built out of different combinations between 6 components which are C atom, N atom, s-triazine, heptazine, heptazine with C atom at the center, and benzimidazole-like component. That results in 20 phases where 11 phases have been previously reported, and 9 phases are newly derived. The partial density of states and charge density have been analyzed through 20 phases to understand the origin of the presence and absence of intrinsic magnetism in GCNs. The intrinsic magnetism will be present not only because the GCNs comprising of radical components but also the $$\pi$$
π
-conjugated states are not the valence maximum to break the delocalization of unpaired electrons. The building blocks are also employed to study alloys between g-$$\hbox {C}_3\hbox {N}_4$$
C
3
N
4
and g-$$\hbox {C}_4\hbox {N}_3$$
C
4
N
3
. The magnetization of the alloys has been found to be linearly dependent on a number of C atoms in the unit cell and some magnetic alloys are energetically favorable. Moreover, the intrinsic magnetism in GCNs can be promoted or demoted by passivating with a H atom depending on the passivated positions.
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