Nitrogen-doped Graphene Nanoribbons Research Articles

Coherent and incoherent phonon transport in periodic nitrogen-doped graphene

Nitrogen-doped graphene materials hold significant promise for diverse applications owing to their exceptional electrical properties and the tunability of thermal conductivity. Therefore, the non-equilibrium molecular dynamics simulations were used to explore the phonon transport properties of nitrogen-doped graphene nanoribbons. The findings indicate that periodic doping with a small quantity of nitrogen atoms can induce coherent phonon transport, thereby resulting in a substantial reduction in thermal conductivity. Our analysis delves into various phonon and energy transport parameters, including the phonon dispersion relation, group velocity, state density, participation rate, and spectral heat flow. Through this examination, we have elucidated the coexistence and transformation mechanisms of both coherent and incoherent phonon transport under different conditions. Furthermore, our findings revealed a notable trend: once the concentration of nitrogen atoms in the doped atomic layer reaches 37.5%, the reduction in thermal conductivity attains its maximum effectiveness. Beyond this concentration, further increases in the nitrogen atom concentration result in diminishing returns, rendering the reduction in thermal conductivity ineffective.

Comparative study of 2D/3D hybrid perovskite solar cell containing different modified carbon nanomaterials based Electron Transport Layers (ETL)

Charge transport facilitation in the electron transport layer is necessary for high-efficiency perovskite solar cells. Carbonaceous materials such as graphene (G) and carbon nanotubes (CNTs) have been extensively used in energy storage and conversion applications. Here we report the novel design of ETL based on the combinations of tin oxide, graphene nanoribbons, nitrogen-doped graphene nanoribbons, and gold nanoparticles for 2D/3D perovskite solar cells. Three different ETLs were employed to get three 2D/3D PSCs with novel device architectures. The effect of different ETLs on the performance of solar cells is investigated. Results reveal that due to better optical and electrical behavior, the solar cell employing a composite of tin oxide, graphene nanoribbons, nitrogen-doped graphene nanoribbons, and gold nanoparticles as ETL has attained a higher PCE of 10.77%.

Hierarchical copper-1,3,5 benzenetricarboxylic acid-MOF-derived with nitrogen-doped graphene nanoribbons as a novel assembly nanocomposite for asymmetric supercapacitors

Hierarchical copper-1,3,5 benzenetricarboxylic acid-MOF-derived with nitrogen-doped graphene nanoribbons as a novel assembly nanocomposite for asymmetric supercapacitors

Tuning NiCo2O4 bifunctionality with nitrogen-doped graphene nanoribbons in oxygen electrocatalysis for zinc-air battery application

• Composites thermally prepared from NiCo 2 O 4 and nitrogen-doped graphene nanoribbons; • Tuning the NiCo 2 O 4 and N-doped graphene ratio tailors the bifunctional activity for ORR and OER; • NiCo 2 O 4 /GNRN-based catalysts as efficient bifunctional catalysts for air electrode of ZAB; • Presence of GNRN proved to be crucial for enhancing the catalysts bifunctionality. One of the major barriers to the widespread use and commercialization of zinc-air batteries (ZAB) is the use of inefficient and expensive bifunctional materials for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysis on the air electrode. Herein, we propose a highly durable ORR/OER bifunctional catalyst, which was thermally prepared using NiCo 2 O 4 blended with nitrogen-doped graphene nanoribbons (GNRN). We evaluated the activity and electrochemical stability of catalysts with different ratios of NiCo 2 O 4 and GNRN as well as the role of each component in the electrocatalytic process to find the most efficient catalyst for both ORR and OER. ORR results revealed that the NiCo 2 O 4 (80):GNRN(20) and NiCo 2 O 4 (90):GNRN(10) novel catalysts exhibited a half-wave potential of ca. 0.79 V RHE in a 4-electron pathway and were practically unaffected by the presence of methanol. With regard to OER, the unblended NiCo 2 O 4 catalyst exhibited the lowest potential required to reach 10 mA cm −2 (1.60 V RHE ), followed by NiCo 2 O 4 (90):GNRN(10) (1.62 V RHE ), and NiCo 2 O 4 (80):GNRN(20) (1.68 V RHE ); however, the presence of tuned amount of N-doped graphene proved to be crucial for enhancing charge transfer, stability, and the ORR/OER bifunctionality of catalysts. After applying NiCo 2 O 4 /GNRN materials and commercial Pt-Ru/C as catalysts in ZAB, the results showed that NiCo 2 O 4 (80):GNRN(20) and NiCo 2 O 4 (90):GNRN(10) exhibited maximum power densities of 78 and 69 mW cm -2 , respectively; these values were quite similar to that obtained for Pt-Ru/C (81 mW cm -2 ). The specific capacity for Pt-Ru/C-based ZAB was 707 mAh g Zn -1 , while both NiCo 2 O 4 /GNRN-based ZABs showed 702 mAh g Zn -1 (86% of the theoretical capacity). Moreover, long-term operation tests involving high current densities and charge-discharge ZAB cycling revealed that NiCo 2 O 4 /GNRN catalysts are clearly more suitable for use at ZAB air electrode than Pt-Ru/C and are as efficient as other non-precious metal catalysts of similar kind which have been reported in the literature.

Single-Atom Low-Valent Alkaline-Earth-Metal Catalysts for Electrochemical Nitrogen Reduction with an Acceptance-Backdonation Mechanism.

Single-atom catalysts (SACs) have drawn great attention in developing highly active and low-cost catalysts for electrocatalytic nitrogen reduction reaction (NRR) in ammonia synthesis, but the atomic metal centers are mainly limited to transition metals. Here, four stable alkaline-earth-metal (AEM)-based SACs are proposed by anchoring AEM on nitrogen-doped graphene nanoribbons, based on first-principles calculations. All SACs exhibit excellent NRR performance with competitive limiting potentials compared to stepped Ru (0001), and Ca-based SAC achieves optimal activity with a potential of -0.716 V. It is revealed that the low oxidation state of AEM is crucial for the activation of N2 through an acceptance-backdonation mechanism. The antibonding 2π* orbital of N2 can accept residual s electrons of low-valent AEM and backdonate electrons to the empty d orbitals of AEM, resulting in activation of N2 molecules. In particular, the activation degree of N2 and NRR activity is linearly associated with the charge states of AEMs. Our work reveals the underlying mechanism of AEMs for N2 activation and reduction and presents the potential of AEM SACs as efficient electrochemical NRR catalysts.

Significantly enhanced thermoelectric performance of Van der Waals interface coupling molecular junction with nitrogen-doped graphene nanoribbon electrodes

Rational design of model structure and effective strategy to overcome inherent mismatch between molecular orbital energy and Fermi level (FL) of electrodes are the key prerequisites to fully rationalize and optimize thermoelectric properties for a single molecular junction. A bis-phenylethynyl-anthrancene (BIS-molecule) with conjugated structure is contacted with armchair/zigzag graphene nanoribbon (AGNR/ZGNR) electrodes by van der Waals (vdW) interface coupling. The optimized distance between molecular and two leads is associated with interface stacking mode. Weak-coupling structure greatly suppresses phonon transport behavior due to interface resistance. Thermal conductance (κtol) has been greatly increased at FL with N-doping based on two different mechanisms. Mass matching effect plays a dominate role for κtol increase in N-doped AGNR_BIS_AGNR, meanwhile sharp and degenerated DOS is main contribution to κtol in N-doped ZGNR_BIS_ZGNR. Nitrogen-doping can adjust Fermi level of electrodes into molecular resonance region, resulting in the enhancement of electronic coupling between central molecular and leads, which is come from obvious charge transfer from graphene nanoribbon to BIS-molecule. Moreover, an excellent thermoelectric figure-of-merit (ZT) of 14.1/3.5 has been obtained near FL for nitrogen-doped molecular junction.

First-principles analysis of aluminium interaction with nitrogen-doped graphene nanoribbons – from adatom bonding to various potential applications

Enhancing aluminium interaction with graphene-based materials is of crucial importance for the development of Al-storage materials and novel functional materials via atomically precise doping. Here, DFT calculations are employed to investigate Al interactions with non-doped and N-doped graphene nanoribbons (GNRs) and address the impact of the edge sites and N-containing defects on the material’s reactivity towards Al. The presence of edges does not influence the energetics of Al adsorption significantly (compared to pristine graphene sheet). On the other hand, N-doping of graphene nanoribbons is found to affect the adsorption energy of Al to an extent that strongly depends on the type of N-containing defect. The introduction of edge −NO group and doping with in-plane pyridinic N result in Al adsorption nearly twice as strong as on pristine graphene. Moreover, double n-type doping via N and Al significantly alters the electronic structure of Al,N-containing GNRs. Our results suggest that selectively doped GNRs with pyridinic N can have enhanced Al-storage capacity and could be potentially used for selective Al electrosorption and removal. On the other hand, Al,N-containing GNRs with pyridinic N could also be used in resistive sensors for mechanical deformation. Namely, strain along the longitudinal axis of these dual doped GNRs does not affect the binding of Al but tunes the bandgap and causes more than 700-fold change in the conductivity. Thus, careful defect engineering and selective doping of GNRs with N (and Al) could lead to novel multifunctional materials with exceptional properties. [Display omitted]

Design principles of nitrogen-doped graphene nanoribbons as highly effective bifunctional catalysts for Li-O2 batteries.

Li-O2 batteries are promising candidates in fields demanding high capacities like electric vehicles due to their superior theoretical energy density in contrast to lithium-ion batteries. However, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the carbonous cathode of Li-O2 batteries are kinetically sluggish. Herein, we explore the electrocatalytic activities, electronic structures, and the underlying catalytic mechanisms of nitrogen-doped graphene nanoribbons (N-GNRs) by density functional theory calculations. The edge effect of zigzag GNRs and the doping effect of nitrogen atoms alter the electronic structure of GNRs and significantly reduce the energy barrier of the two-electron ORR/OER. The overpotential of the GNRs can reach 0.025 V, demonstrating better catalytic activity than the noble metals Ag(111) and Au(100). Four-electron preferential sites also exist in N-GNRs, usually located at the center of the nanoribbons and far away from the nitrogen atom.

Significantly Enhanced Thermoelectric Performance of Van Der Waals Interface Coupling Molecular Junction with Nitrogen-Doped Graphene Nanoribbon Electrodes

Significantly Enhanced Thermoelectric Performance of Van Der Waals Interface Coupling Molecular Junction with Nitrogen-Doped Graphene Nanoribbon Electrodes

Unveiling bonding states and roles of edges in nitrogen-doped graphene nanoribbon by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) is among the most utilized analytical methods for nitrogen-doped carbon materials. Clarifying the assignments of nitrogen-doped carbon materials with different degrees of carbonization, which relates to conjugated systems, is essential to correlate structures with the performance of various applications, but such precise assignments were challenging. In this work, precise analyses were conducted to overcome the difficulty to assign the peaks of carbon materials with different degrees of carbonization, different edges, and various nitrogen-containing functional groups in graphene nanoribbons (GNRs), such as nitrile, pyridinic, primary with/without charges, secondary with/without charge, tertiary without charges (graphitic nitrogen), and quaternary nitrogen. Electrons donated from hydrogen and Madelung potentials showed a higher correlation to the peak shift of C1s and N1s XPS spectra than Mulliken charges on nitrogen. Zigzag edges showed a greater influence on the peak shift of tertiary amine (graphitic nitrogen) than armchair edges on XPS spectra. Besides, as the degree of carbonization is increased from aromatic compound-like structures to GNRs, the peak positions of C–N in C1s and N1s XPS spectra shifted to higher binding energies. This research proved that XPS could be applied to the precise structural analyses of nitrogen-containing carbon materials.

Hetero-Dimensional 2D Ti3C2Tx MXene and 1D Graphene Nanoribbon Hybrids for Machine Learning-Assisted Pressure Sensors.

Hybridization of low-dimensional components with diverse geometrical dimensions should offer an opportunity for the discovery of synergistic nanocomposite structures. In this regard, how to establish a reliable interfacial interaction is the key requirement for the successful integration of geometrically different components. Here, we present 1D/2D heterodimensional hybrids via dopant induced hybridization of 2D Ti3C2Tx MXene with 1D nitrogen-doped graphene nanoribbon. Edge abundant nanoribbon structures allow a high level nitrogen doping (∼6.8 at%), desirable for the strong coordination interaction with Ti3C2Tx MXene surface. For piezoresistive pressure sensor application, strong adhesion between the conductive layers and at the conductive layer/elastomer interface significantly diminishes the sensing hysteresis down to 1.33% and enhances the sensing stability up to 10 000 cycles at high pressure (100 kPa). Moreover, large-area pressure sensor array reveals a high potential for smart seat cushion-based posture monitoring application with high accuracy (>95%) by exploiting machine learning algorithm.

Fjord-Edge Graphene Nanoribbons with Site-Specific Nitrogen Substitution.

The synthesis of graphene nanoribbons (GNRs) that contain site-specifically substituted backbone heteroatoms is one of the essential goals that must be achieved in order to control the electronic properties of these next generation organic materials. We have exploited our recently reported solid-state topochemical polymerization/cyclization-aromatization strategy to convert the simple 1,4-bis(3-pyridyl)butadiynes 3a,b into the fjord-edge nitrogen-doped graphene nanoribbon structures 1a,b (fjord-edge N2[8]GNRs). Structural assignments are confirmed by CP/MAS 13C NMR, Raman, and XPS spectroscopy. The fjord-edge N2[8]GNRs 1a,b are promising precursors for the novel backbone nitrogen-substituted N2[8]AGNRs 2a,b. Geometry and band calculations on N2[8]AGNR 2c indicate that this class of nanoribbons should have unusual bonding topology and metallicity.

Bottom-up Synthesis of Nitrogen-Doped Porous Graphene Nanoribbons.

Although methods for a periodic perforation and heteroatom doping of graphene sheets have been developed, patterning closely spaced holes on the nanoscale in graphene nanoribbons is still a challenging task. In this work, nitrogen-doped porous graphene nanoribbons (N-GNRs) were synthesized on Ag(111) using a silver-assisted Ullmann polymerization of brominated tetrabenzophenazine. Insights into the hierarchical reaction pathways from single molecules toward the formation of one-dimensional organometallic complexes and N-GNRs are gained by a combination of scanning tunneling microscopy (STM), atomic force microscopy (AFM) with CO-tip, scanning tunneling spectroscopy (STS), and density functional theory (DFT).

Theoretical Study on a Nitrogen-Doped Graphene Nanoribbon with Edge Defects as the Electrocatalyst for Oxygen Reduction Reaction.

Both theory and experiment show that sp2 carbon nanomaterials doped with N have great potential as high-efficiency catalysts for oxygen reduction reactions (ORR). At present, there are theoretical studies that believe that C-sites with positive charge or high-spin density values have higher adsorption capacity, but there are always some counter examples, such as the N-doped graphene nanoribbons with edge defects (ND-GNR) of this paper. In this study, the ORR mechanism of ND-GNR was studied by density functional theory (DFT) calculation, and then the carbon ring resonance energy was analyzed from the perspective of chemical graph theory to elucidate the cause and distribution of active sites in ND-GNR. Finally, it was found that the overpotential of the model can be adjusted by changing the width of the model or dopant atoms while still ensuring proper adsorption energy (between 0.5 and 2.0 eV). The minimum overpotential for these models is approximately 0.36 V. These findings could serve as guidelines for the construction of efficient ORR carbon nanomaterial catalysts.

Electronic and transport characteristics of vacancy and nitrogen-doped graphene nanoribbon rotational switch

The effect of nitrogen (N) doping and single vacancy defect is investigated on the electromechanical properties of twisted armchair graphene nanoribbon (TAGNR). Five different twist angles were investigated for the perfect model, N doping and single vacancy defect which are located in three different positions and in three different widths of AGNR. In general, 105 models were produced with this specification. The results show that among the above models, eight devices with suitable switching behavior can be selected as the first graphene-based nanoribbon rotational switch (GRS) with defect and doping. The combination of density function theory (DFT) and the non-equilibrium Green's function methods were utilized in the computation. Having applied the twist, the bond length structure of the atoms, the charge density distribution, and transmission pathways vary leading to the different strain energies and change in the electronic behavior of the device. The change in the twist angle causes the maximum and minimum currents of the device able to increase or decrease in the value of these changes through creating defect and doping in the structure which, also, relies on the defect or doping and their position. Based on the above results, applying electromechanical changes therein can control the electronic properties of the device.

Electronic Transport Characteristics of a Graphene Nanoribbon Based p–n Device

Electronic transport in terms of its parameters, such as electron effective mass, electron mobility, deformation potential (DP), electron Fermi velocity and energy band gap, is investigated for a boron and nitrogen codoped armchair graphene nanoribbon (aGNR) based p–n device via determination of electron interaction with acoustical phonons by deformation potential (DP) scattering mechanism and piezoelectric (PZ) scattering mechanism under the impact of finite electric field at low temperature regime. The variation of acoustical deformation potential (ADP) with electron Fermi velocity for a particular temperature has been studied. The dependence of electron mobility on the doping concentration as well as electron effective mass and lattice temperature have been observed for a boron and nitrogen doped graphene nanoribbon p–n device for its nanoelectronic and photovoltaic applications. The current-voltage characteristics have also been studied for the p–n device under the forward biased condition. The net electron mobility (ADP + PZ) for the region of boron doped aGNR is observed much higher in comparison with the region of nitrogen-doped graphene for a particular temperature. Moreover, it has also been observed that the electron mobility increases with boron doping in the P-region, but decreases with an increase in nitrogen concentration in the N-region of the armchair graphene nanoribbon based p–n device. The band gap shows considerable variation with impurity concentration for the width of nanoribbons less than 40 nm with respect to pristine graphene, whereas for that with widths of more than 50 nm to up to 100 nm there is no impact of concentration on the band gap.

(Invited) Atomically Precise Graphene Nanoribbons: From Synthesis to Applications

Atomically precise graphene nanoribbons (GNRs) are at the forefront of nanocarbon research and hold great promise for electronic and optoelectronic applications. Theoretical studies have shown that narrow GNRs possess interesting electronic and magnetic properties that strongly depend on the nanoribbon’s width and edge structure. GNRs with different structures can be synthesized with atomic precision and fine-tuned properties by coupling properly designed molecular precursors and planarization of the resulting polymers. In this talk, I will discuss our efforts on designing and synthesizing new atomically precise GNRs for electronic applications. First, I will describe a scalable bottom-up solution approach for atomically precise GNRs that is based on Yamamoto coupling of pre-synthesized molecular precursors followed by cyclodehydrogenation using Scholl reaction. This approch can be applied to the synthesis of a variety of GNRs, including pristine and nitrogen-doped GNRs with the chevron structure. Then, I will demonstrate that the electrical conductivity of atomically precise chevron GNRs can be improved by their lateral extension. Two types of new laterally extended chevron GNRs (eGNRs) were synthesized in solution, and their high structural quality was confirmed by a number of characterization techniques, including high-resolution scanning tunneling microscopy and Raman spectroscopy combined with a computational analysis. Optical spectroscopy and scanning tunneling spectroscopy showed that lateral extension of chevron GNRs resulted in the decrease of their electronic bandgap. We developed a procedure for processing eGNRs into uniform thin films that exhibit improved electrical conductivity compared to similar films of regular chevron GNRs. The eGNR films were employed in gas sensors that showed very high responsivity to low molecular weight alcohols compared to similar sensors based on benchmark graphitic materials, such as graphene and graphene oxide. Finally, we demonstrated the first electronic nose system based on atomically precise GNRs that could reliably recognize analytes of nearly the same chemical nature, such as methanol and ethanol. Overall, this talk will demonstrate the entire path from designing new atomically precise GNRs with improved properties to their bottom-up synthesis, characterization, processing and implementation in electronic devices.

Nanostructured porous carbons derived from nitrogen-doped graphene nanoribbon aerogels for lithium–sulfur batteries

A nanostructured porous carbon (NPC) is prepared by using a facile physical activation method, with nitrogen-doped graphene nanoribbon aerogel and carbon dioxide as a precursor and an activating agent, respectively. The morphology, porosity parameters, and chemical properties of the as-prepared NPC have been revealed by using various characterization methods, including scanning electron microscopy, nitrogen sorption analysis, and X-ray photoelectron spectroscopy (XPS). The NPC with a moderate nitrogen content (5.1 atom % on the basis of XPS analysis) retains the sponge-like morphology of nitrogen-doped graphene nanoribbon aerogel, shows a high Brunauer–Emmett–Teller specific surface area (1380 m2 g−1), and possesses hierarchically porous structures. Based on its excellent properties such as high porosity, conductive network, and nitrogen-doping, NPC as a superior host is used to fabricate a sulfur-based cathode for lithium–sulfur batteries. The high specific surface area and the pore volume of NPC not only allow uniform distribution of sulfur in an amorphous form, but also help to alleviate the shuttle effect of polysulfides. As a result, the as-obtained cathode exhibits a good rate capability and cycling stability.

Thermal properties of triangle nitrogen-doped graphene nanoribbons

We investigate the thermal properties of triangle nitrogen-doped graphene nanoribbons (TNGNs) with different nitrogen-doped concentrations (0.11% to 2.31%) at different temperatures (200K∼600K) using non-equilibrium molecular dynamics. The results show that the nitrogen atoms doped at the edge of the defect can increase the thermal conductivity of graphene nanoribbons, but with the increase of the nitrogen-doped concentrations from 0.11% to 2.31%, the thermal conductivity decreases sharply. In addition, nitrogen atoms reduces the sensitivity of the thermal conductivity to temperature. Besides, the thermal rectification is found, and it increases with the raise of nitrogen-doped concentration. Finally, in order to verify the correctness of the thermal rectification, we calculate the phonon power spectra of TNGNs with nitrogen-doped concentrations of 0.11% and 2.31% at 300 K. These research has important reference value for the control of heat in microelectronic devices.

Non-collinear magnetism and electronic transport of boron or nitrogen doped zigzag graphene nanoribbon

Zigzag graphene nanoribbon (ZGNR) is important for novel carbon-based spintronic applications. Currently, most of ZGNR spintronic studies focus on the collinear magnetism where the up-spin and down-spin are separated clearly. But in some cases, e.g. doping and adsorption, the magnetization profile can be modulated and thus noncollinear magnetism can occur. In order to shed light on possible noncollinear magnetism in ZGNR, we study non-collinear magnetism and electronic transport of boron or nitrogen-doped zigzag graphene nanoribbon based on noncollinear density functional theory and non-equilibrium Green's function method. For pristine ZGNR, our results show that the ZGNR presents helical magnetization distribution due to noncollinear magnetization in left and right lead. As the ZGNR is doped with boron and nitrogen atoms, the ZGNR shows a characteristic two-zone feature in the magnetization distribution. Near the dopant site, the magnetic moment of carbon atom is small. However, the magnetic moments of carbon atoms in the left (right) region of dopant are close to those of the left (right) lead. Such a feature provides the possibility of constructing domain walls with various widths on the edge of ZGNR. Moreover, the transmission at the Fermi level (<i>E</i> = 0 eV) decreases with the increase of relative angle between magnetizations of left and right lead, indicating that the spin-flip scattering dominates the electronic transport. However, at <i>E</i> = ±0.65 eV, there is a transmission dip with low transmission, which implies that the dopant induces the strong backscattering. To understand the origin of this dip, we calculate the density of states (DOS) and project the DOS onto each atom of doped ZGNR. The projected DOS shows a large and broad peak at <i>E</i> = −0.65 eV for N-doped ZGNR but at <i>E</i> = +0.65 eV for B-doped ZGNR. The consistency between the position of dip in transmission and the position of peak in DOS indicates that the transmission dip mentioned above is attributed to strong backscattering from the dopant-induced bound state. Our theoretical results are expected to be useful for understanding the noncollinear magnetism and spin scattering in the doped ZGNR-based devices. Also, our work provides a considerable insight into the design of ZGNR-based nanoelectronic devices, such as the transistor based on spin transfer torque effect.