Nitrogen doped graphene is a new material that is attracting much attention in the scientific community. It is being researched for applications in semiconductors and organic photovoltaic devices. Graphene is a one-atom-thick layer of carbon that has the potential to provide a variety of advantages over conventional silicon-based materials. For example, nitrogen doped graphene has the potential to improve the efficiency of solar cells and photovoltaic devices.
TEM image of graphene oxide
One of the major advances in the study of graphene was its doping with nitrogen. It has opened a new field of research and will impact the development of electronics. The doping of graphene requires more detailed studies. Here we present experimental results of p- and n-type doped graphenes. We also demonstrate the effects of surface transfer doping.
N-doped graphene has several advantages over pristine graphene. First, it has a lower energy barrier for ORR. In addition, it has four times higher capacitance. This makes it a potential supercapacitor. Other advantages include its ability to improve device performance. Moreover, it is a promising material for metal-free electrocatalysis in ORR.
Several TEM images have been published, which reveal the morphology and structure of the doped graphene. For example, the HR-TEM image of the SnO2-N-doped graphene composite shows both the pristine and doped layers. Also, the HR-TEM image of the N-doped single-layer graphene and the tri-layer graphene show their layered structure and the multi-oriented hexagonal lattice of the graphene framework.
Similarly, the EELS atomic spectra of FeN4/GN show the Fe-Nx bonding, which is further supported by XRD. In addition, the SAED pattern reveals the original honeycomb-like atomic structure of the graphene.
Nevertheless, unintentional doping can alter the surface of the graphene, which could affect its function. Especially, it would be necessary to use more accurate methods for doping. Using SnO2 nanocrystals in combination with N-doped graphene has a synergistic effect, which can save time in syntheses.
Electrochemical performances of pure Gh and N-Gh samples
This strategy is advantageous for ion storage and transport in the electrolyte. It also enhances the conductivity of the material.
After the co-doping process, the FGH-4 sample displayed excellent capacitive characteristics. The sample maintained 99.5% capacitance after 1,000 cycles.
At 50 mV/s, the CV curves of FGH-4 showed symmetric redox peaks after 1,000 cycles. The Warburg line was significantly shorter than those of other samples. These results indicate that the FGH-4 exhibited EDLC behavior.
GO and nitrogen-containing functional groups on the graphene sheets resulted in a higher number of defects. Furthermore, hydrogen bonds promoted the expansion of the space between the sheets.
As a result, the FGH-4 exhibited a higher specific surface area than the GH. This increased the capacity of the FGH-4 electrode material. The sulfide coating ensures access to the electrolyte and reduces the ion diffusion path.
The electrode materials of FGH-4 showed excellent capacitive properties and had outstanding cycle stability. They exhibited an ID/IG value that was much higher than that of the GH. The sulfide coating was also a suitable stabilizer for the electrolyte ion storage.
Compared with the GH, the FGH-4 electrode had a longer charge and discharge time. Moreover, its CV curves at 50 mV/s were almost perfect rectangles before the thousand-cycle testing. All these results indicate that the FGH-4 has promising potential as the electrode material of SCs.
Induction or suppression of defects in graphene or other bilayer or few layer heterostructures
Defects in graphene and other heterostructures are a major cause of distortions in both the XPS and mechanical properties of these materials. However, defects can be suppressed or induced to alter the properties of heterostructures. In particular, defects affect the electrical and thermal conductivity of graphene-based heterostructures. This can lead to intriguing and unconventional architectures.
There are two general types of defects: substitutional and nonsubstitutional. The substitutional type of defect requires a complex of at least two to four vacancies.
Defects can also modulate the electrical and thermal responses of Gr-based heterostructures. The geometric morphology of the structure is based on the type of defects present. It depends on the defect structure and the interaction between the defect and the environment.
Using XPS measurements, we have investigated the formation and evolution of defect complexes in bilayer graphene. In particular, we found that the intensity of the double resonant Raman process increases with the number of defects. Moreover, the intensity of the D band is significantly increased in the presence of defects. The peak in the D band occurs at a relatively low energy (1350 cm-1) in the presence of defects.
XPS surveys of defects in bilayer graphene reveal that the concentration of nitrogen atoms on defects increases with nitrogen content in the bilayer material. Despite this, the formation energy of the defect in monolayer does not change. A sample NG3 shows a saturation of nitrogen incorporation.
Although defects are not the only factor that influences the mechanical behavior of bilayer graphene, they are an important part of the puzzle. For example, defects are responsible for missing momentum in the double resonant Raman process.
Luminscent graphene quantum dots for organic photovoltaic devices
Graphene quantum dots (GQDs) are emerging luminescent materials. Their properties are highly promising. They are tunable in electronic and optical properties, making them ideal candidates for various applications in bioimaging and sensing.
Recent studies have reported power conversion efficiencies of ca 14% in single-solar cells. However, the efficiency of donor-acceptor blended bulk heterojunction organic photovoltaic devices is still insufficient. In this article, we explore how to improve the efficiency of these devices by using graphene quantum dots.
Graphene quantum dots have good dissolution in polar solvents, such as water, and their size is very small. A typical nanoparticle has a diameter of 2-8 nm. The synthesis process is relatively simple.
Additionally, carbon quantum dots have a unique optical property. When illuminated with UV light, the nanoparticles have blue luminescence.
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