Nitrogen doped graphene is a material derived from graphene. Graphene is an amorphous, two-dimensional material made up of two layers and a single atom. The researchers investigated the structure and properties of graphene by using X-ray powder diffraction, Raman spectroscopy, and FTIR. These techniques provided information about the size of the graphene crystallites, the number of layers, and the functionalities attached to the graphene surface.
X-ray powder diffraction pattern
An X-ray powder diffraction study of nitrogen doped graphene revealed a new morphology, involving the formation of an edge plane. This morphology is related to the presence of nitrogen and sulfur atoms. Another way to investigate the properties of nitrogen doped graphene is by studying its structure and composition. Nitrogen doped graphene has different atomic ratios than graphene with carbon atoms. As a result, nitrogen doped graphene has a distinct structure and morphology.
X-ray photoelectron spectroscopy
The X-ray photoelectron spectra of nitrogen-doped graphene reveal the presence of defects in the structure. In particular, N-related defects show the splitting of the signal. This splitting is related to the nitrogen atom that bridges two graphene layers.
XPS is a powerful tool for analyzing chemical modifications on surfaces, and it can also be used to investigate heteroatom dopants in carbon nanomaterials. Although carbon nanomaterials possess superb intrinsic properties, they often need to undergo controlled modification for specific applications. Boron and nitrogen are the most popular dopants in carbon nanomaterials, but phosphorus is a novel alternative that has recently received attention. Hundreds of studies have used XPS to characterize dopants in various materials, but most of the focus has been on nitrogen. Important research is underway to determine the exact atomic bonding configuration of nitrogen.
Nitrogen atoms in graphene improve many properties of carbon materials, including electrochemical capacity in Li-ion batteries. The effect of nitrogen on graphene is evident in model experiments. N-doped graphene films were grown by chemical vapor deposition on copper, acetonitrile, and SiO2/Si substrates. These films were then subjected to XPS to study their electronic structures before and after lithium evaporation.
The spectral range of nitrogen doped graphene is dominated by two peaks in the N-D region. Each of these peaks has a different chemistry, and the energy difference between the two peaks is about 0.9 eV.
High-resolution XPS spectra
In-situ high-resolution XPS spectra and temperature-programmed XPS spectra of nitrogen-doped graphene have been reported. NDG was synthesized by low-energy nitrogen implantation on a Ni(111) substrate. After implantation, hydrogenation of the NDG was carried out. The resulting spectra revealed a new peak associated with the CH groups. It also revealed a new peak associated with graphitic and pyridinic nitrogen.
The high-resolution XPS spectra obtained from nitrogen-doped graphene are crucial for determining the structure of these materials. They show the structure-to-property correlations of the materials. However, they are difficult to interpret due to the uncertainties involved in peak identification. Therefore, they should be complemented by other analytical methods.
The study also included XPS survey spectra of GO and N-rGO samples. This means that the sample’s crystallinity has increased. Additionally, the calculated crystallite size (Lc) agrees with the measured size using Scherer’s equation. Moreover, N-rGO3 shows a higher Lc value than N-rGO1 and N-rGO2.
Nitrogen doping improves the conductivity of graphene by reducing the inner resistance of the graphene. It also improves the wettability of the electrode interface. In electrochemical studies, N-doped graphene-based particle electrodes showed excellent performance as supercapacitor electrodes. The electrodes exhibited a high specific capacitance of 280 F g-1 at 5 mV s-1 and good cycling stability. After forty thousand cycles, the electrode still retained 94% of its capacitance.
Nitrogen has been attracting a lot of attention recently for its superior electrochemical stability. However, doping nitrogen within a carbon matrix can lead to defects due to differences in atomic radius and bond length. In addition, doping causes the carbon atoms to become positively charged (C(d+)) which promotes the adsorption of O2 molecules. Furthermore, it can promote reactions with the oxygen molecule.
The conductivity of nitrogen doped graphene is greater than that of the traditional PEDOT:PSS nickel oxides. Furthermore, the nitrogen dopant in graphene enhances the interfacial interactions between two surfaces, allowing for more energy to flow in and out of the material. This means that N-doped graphene has greater sensitivity and can replace traditional PEDOT: PSS nickel oxides in electronic devices.
We have investigated the solution processability of nitrogen doped graphene. By introducing H2 flow and ACN vapor, we were able to initiate the first nucleation of Nc-G on Cu foil. We found that the nitrogen incorporation was triggered at vacancies in the starting material. We then rationalized the side-reaction pathways and carried out GC-MS analysis to confirm the byproducts. Furthermore, we observed that the nucleation density was high and the NG grains showed a wide distribution of domain sizes.
Incorporation of nitrogen is favorable and requires that the defect complexes contain two to four vacancies. A large concentration of vacancies due to PECVD is needed for nitrogen incorporation. In addition, we observed that the XPS curves of the different samples showed qualitative differences in the defect complexes.
Nitrogen doping of graphene is feasible under mild and low energy conditions. However, the process should be homogeneous, and the product should have high nitrogen content. A solution of NaNH2 and fluorographene is a good candidate for N-doped graphene preparation.
We have successfully applied the alternating voltage electrochemical method to produce nitrogen doped graphene on a large scale. By adding N-Gh to a NaOH aqueous solution, we were able to produce a larger N-Gh sample than pure graphene. We investigated the N-Gh sample in three-electrode and two-electrode systems and found that it displays satisfactory rate behavior with long cycling stability.
Surface functionalization of nitrogen doped graphene is a promising approach to improving graphene’s properties. The resulting material possesses a higher center of ID/IG distribution and cluster slope than undoped graphene. In addition, the resulting N-doped graphene exhibits an increased G-to-D band correlation.
The process of nitrogen doping graphene involves adding chemical species to the material. The results of the XPS and FTIR studies show that nitrogen doping produces nitrogen-containing groups. These findings indicate that the surface of N-doped graphene is highly functional.
Surface functionalization of nitrogen doped graphene has significant implications for the catalytic activity of graphene. The incorporation of nitrogen generates defect sites and enhances the surface energy and physical/chemical properties. Recent studies have focused on the potential of N-doped carbons as catalysts in CO2 capture and conversion. In a recent paper, Wang et al. reported that nitrogen-doped graphene is a highly effective catalyst for cycloaddition reactions.