Nitrogen-doped Graphene Nanosheets Research Articles

Machine Learning-Assisted design of boron and nitrogen doped graphene nanosheets with tailored thermomechanical properties

Doping graphene with boron and/or nitrogen enhances its potential for various applications, such as electronics and energy devices. However, these modifications impact the material's properties, influencing its response to external forces, temperature, and heating. Investigating the connection between the structure of co-doped graphene nanosheets and their thermomechanical properties is crucial for accurate predictions and tailored nanosheet engineering. In the present study, molecular dynamics (MD) simulations were performed to compute the thermal and mechanical properties of 300 randomly generated boron/nitrogen co-doped graphene nanosheets with doping concentrations in the range of 0%-15%. Next, the obtained MD results were used to train, tune, and validate a wide spectrum of supervised machine learning models, including linear regression models, regression trees, support vector machines, Gaussian process regression models, kernel approximation models, ensembles of regression trees, and regression neural networks. Our aim is to find models that better estimate, without overfitting, the structure-properties relation of boron/nitrogen co-doped nanosheets. To this end, the models with the highest coefficient of determination (R2) and the lowest root mean square error (RMSE) were utilized. Finally, an appropriate implementation of guided random search algorithms, mainly Genetic Algorithms, was used to solve the inverse problem, i.e., find the nanosheet structure which exhibits the desired set of property values. To this end, thermal conductivity, Young’s modulus, failure stress, and failure strain were specified as target values. A detailed comparison between the employed models and their validation via MD simulations is also included. The achieved results provide sufficient evidence of the accuracy and viability of the applied procedure in both prediction of thermomechanical properties as well as identification of structures with desired properties. This study provides a roadmap that could help scientists and engineers develop nanosheets-based materials with tunable thermomechanical properties, ultimately leading to the creation of innovative and high-performance technologies.

3D binder-free nanoarchitecture design of porous silicon/graphene fibers for ultrastable lithium storage

Enhancing the stability and fast-charging capability of battery electrodes is of paramount importance in the field of battery technology. Silicon (Si), renowned for its high specific capacity, has emerged as a promising candidate for anodes. However, the limited structural stability and electron/ion conductivity of silicon-based anodes have raised significant concerns, including fractures and the continuous formation of unstable solid-electrolyte interphase (SEI) layers, leading to rapid capacity decay. In this study, we introduce a comprehensive approach to fabricating a binder-free and free-standing anode electrode paper using a combination technique of employing electrospinning, magnetron sputtering, and chemical vapor deposition (CVD) techniques. This developed paper electrode incorporates a 3D interconnected network of nitrogen-doped vertical graphene nanosheets (VGs) that connect porous carbon fibers (PCFs) with uniformly distributed Si nanoparticles (VGs@Si@PCFs). The as-fabricated VGs@Si@PCFs paper effectively addresses the mechanical and chemical stability issues commonly associated with Si anodes. The VGs@Si@PCFs anode demonstrates a remarkable reversible capacity of 2205 mAh g-1 at 0.1 A g-1 and exhibits exceptional cycling performance with 83.5% capacity retention at 1.0 A g-1 after 3000 cycles. This design leverages the nanoporous carbon fibers and nitrogen-doped vertical graphene nanosheets as flexible and conductive supports, enhancing the robustness and flexibility of the electrode. Additionally, mechanical modeling reveals that the overall Mises strain in the porous VGs@Si@PCFs structure is significantly lower compared to nonporous cases, potentially minimizing low-cycle fatigue. Our free-standing Si/C composite anode introduces a new class of low-strain Si-based materials, showcasing significantly improved stabilities and fast-charging capabilities.

Synthesis of new Pd@NDG electrocatalyst by using g-C3N4/GO hydrogel toward formic acid electrooxidation reaction in direct formic acid fuel cell

In this research, the new Pd@NDG electrocatalyst was evaluated for the formic acid oxidation reaction. The nitrogen-doped graphene nanosheets (NDG) support was obtained by heating the g-C3N4/GO hydrogel in an inert atmosphere. The Pd@NDG electrocatalyst was prepared by combined use of NDG and palladium chloride via a one-stage reduction using ascorbic acid. The as-prepared Pd@NDG electrocatalyst displayed high catalytic activity in formic acid oxidation. The significant electrocatalytic performance stems from the presence of the NDG support in the structure of the electrocatalyst. The NDG support improved the physicochemical properties of the catalyst. The NDG support acts as an excellent ligand and leads to increase dispersion of Pd. The number of active metal sites is enhanced by increasing dispersion and exposing the surface area of the electrocatalyst and improving electronic properties, which lead to improving the catalytic performance of the catalyst. Furthermore, the formic acid electrocatalytic activity and the durability of Pd@NDG electrocatalyst as compared to the Pd/C commercial benchmark catalyst. The results displayed that the Pd@NDG electrocatalyst has better performance for formic acid oxidation.

Comparing Pt electrodeposition processes on nitrogen-doped graphene nanosheets for the electroreduction of oxygen

Comparing Pt electrodeposition processes on nitrogen-doped graphene nanosheets for the electroreduction of oxygen

Theoretical insights into heteronuclear dual metals on non-metal doped graphene for nitrogen reduction reaction

Electrochemical nitrogen reduction reaction (eNRR) is a promising strategy for sustainable ammonia production. To achieve high yield and energy efficiency, single-atom dispersion on nitrogen-doped graphene nanosheets has been extensively explored as an electrocatalyst for eNRR. However, challenges remain owing to the high overpotentials arising from unitary active sites and unabundant ligands. In this study, heteronuclear dual-metal catalysts with different non-metals doped in a graphene frame were computationally designed. After a two-step scanning based on density functional theory calculations, five candidates, namely FeMo-S, RuMo-B, RuMo-P, RuMo-S, and RuW-S, were identified as promising catalysts with calculated onset potentials of –0.18, –0.25, –0.27, –0.29, and –0.24 V, respectively. These catalysts can also effectively suppress the competitive hydrogen evolution reaction during NRR. Such excellent catalytic performance origins from two synergetic effects: (1) the cooperation of heteronuclear metals contribute to the electron transfer from active sites to the anti-bonding orbitals of N2 molecules adsorbed on catalysts to effectively activate N≡N bonds; (2) metal-ligands (non-metals) interactions moderate the binding strength of intermediates to slab, which is one of reasons for low NRR onset potential and high NH3 selectivity. The present study provides a theoretical understanding of the NRR mechanism of dual-metal catalysts, offering useful guidance for the rational design of catalysts with high selectivity and activity for NRR.

Nitrogen‐Doped Graphene Nanosheets for Sustainable Removal of Pharmaceutical Contaminants from Water: Kinetics and ANFIS Modeling

AbstractIn this work, nitrogen‐doped graphene nanosheets (NGS) were synthesized to remove diclofenac sodium (DFS) from water. The NGS exhibited 99.8 % removal efficiency, adsorption capacity of 278 mg g−1 for DFS within 30 min, and excellent reusability up to 5 cycles of adsorption. The experimental data fit well with pseudo‐second order kinetic model and Langmuir isotherm model. X‐ray photoelectron spectroscopy (XPS) and FTIR studies revealed that the carboxylic group, triazine group, graphitic‐N, and pyridinic‐N groups were involved in the adsorption of DFS. The adaptive neuro‐fuzzy inference system (ANFIS) was modeled for accurate prediction of optimizing parameters for the maximum adsorptive removal (%) of DFS by NGS. A subsequent cytotoxicity assay of NGS on a green alga Chlamydomonas sp. signified non‐toxic nature. This study suggests NGS to be a promising economic adsorbent for water remediation in resource‐poor environments to fulfill “UN‐Sustainable Development Goal‐ 6”.

Iron single Atom–Iron nanoparticles dual-deposited nitrogen-doped graphene hybrid as an innovative catalyst to enhance the oxygen reduction reaction

The fabrication of an effective electrocatalyst for cathodic oxygen reduction reaction (ORR) is important to enhance the performance of fuel cell applications. Here, we prepared a novel hybrid material based on the combination of iron single atoms–small iron nanoparticles homogeneously distributed on the surface of nitrogen-doped graphene nanosheets (FeSA-FeNPs/NG). The achieved FeSA–FeNPs/NG material exhibited high catalytic ORR behaviors with high positive values of +0.94 V and +0.81 V for onset potential and half-wave potential, respectively, as well as the remarkable stability with 90% retention of initial current over an operation period of 15 000 s), superior to commercial Pt/C in 0.1 M KOH medium. In addition, the material favored a four-electron reaction pathway along with good methanol crossover tolerance towards ORR. The outstanding catalytic performance could be attributed to the formation of a unique microporous nanoarchitecture owning large specific surface area of 103.63 m2 g−1 and high conductivity, which create rich active sites and fast charge transfer ability, thus effectively accelerating the adsorption and catalyzation processes to convert oxygen reactant to product during ORR. These findings suggest a novel route for the synthesis of potential catalysts exhibiting excellent efficiency and cost effectiveness for fuel cell industries.

Synthesis of nitrogen-doped graphene and its strengthening effect on aluminium metal matrix composite

The present study investigates the potential of nitrogen-doped graphene nanosheets (NDG) as a reinforcing material in aluminum (Al) metal matrix composites. The NDG was synthesized through a mechanochemical process involving solid-state dry ball milling of graphite with melamine. Characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were used to evaluate the properties of the NDG. For the first time, NDG was employed as a reinforcing material to improve the wettability, minimize the formation of aluminum carbide, and enhance the strength through strong interfacial bonding. The ultimate tensile and compressive yield strengths of Al/NDG composites were found to be 124% and 67% higher, respectively, with only 0.2 wt% NDG content. Furthermore, the tensile strength of the 0.2 wt% NDG/Al composite was found to be 72% higher than that of the 0.5 wt% graphene/Al composite. The fractured surface of the Al/NDG composite was investigated by XRD and FESEM techniques. XRD analysis revealed the presence of low-intensity peaks of aluminum nitride (AlN) and no evidence of aluminum carbide. The tribological properties of NDG were studied through wear rate and coefficient of friction (COF) measurements. The results showed a decrease in COF by 45% with an increase in NDG concentration from 0.1 to 0.5 wt%, and a decrease in wear rate by 25% and 71% for the same NDG concentration range. These results provide insight into the potential of NDG as an additive to improve tribological properties in aluminum-based composites. Further research is needed to understand the underlying mechanisms and optimize the performance thoroughly.

The New Materials for Battery Electrode Prototypes.

In this article, we present the performance of Copper (Cu)/Graphene Nano Sheets (GNS) and C-π (Graphite, GNS, and Nitrogen-doped Graphene Nano Sheets (N-GNS)) as a new battery electrode prototype. The objectives of this research are to develop a number of prototypes of the battery electrode, namely Cu/GNS//Electrolyte//C-π, and to evaluate their respective performances. The GNS, N-GNS, and primary battery electrode prototypes (Cu/GNS/Electrolyte/C-π) were synthesized by using a modified Hummers method; the N-doped sheet was obtained by doping nitrogen at room temperature and the impregnation or the composite techniques, respectively. Commercial primary battery electrodes were also used as a reference in this research. The Graphite, GNS, N-GNS, commercial primary batteries electrode, and battery electrode prototypes were analyzed using an XRD, SEM-EDX, and electrical multimeter, respectively. The research data show that the Cu particles are well deposited on the GNS and N-GNS (XRD and SEM-EDX data). The presence of the Cu metal and electrolytes (NH4Cl and MnO2) materials can increase the electrical conductivities (335.6 S cm-1) and power density versus the energy density (4640.47 W kg-1 and 2557.55 Wh kg-1) of the Cu/GNS//Electrolyte//N-GNS compared to the commercial battery (electrical conductivity (902.2 S cm-1) and power density versus the energy density (76 W kg-1 and 43.95 W kg-1). Based on all of the research data, it may be concluded that Cu/GNS//Electrolyte//N-GNS can be used as a new battery electrode prototype with better performances and electrical activities.

Anisotropic thermoelectric properties in hydrogenated nitrogen-doped porous graphene nanosheets.

By using density functional theory calculations combined with the nonequilibrium Green's function method and machine learning, we systematically studied the thermoelectric properties of four kinds of porous graphene nanosheets (PGNS) before and after nitrogen doping. The results show that the thermoelectric performance of porous graphene nanosheets along the armchair or zigzag chiral direction is improved due to the dramatically enhanced power factor caused by nitrogen doping. The calculated ZT values of nitrogen-doped porous graphene nanosheets are boosted by about one order of magnitude compared with those of undoped porous graphene nanosheets at room temperature. More importantly, an anisotropic thermoelectric transport is found in the nitrogen-doped porous graphene nanosheets. The results show that the ZT values of nitrogen-doped porous graphene nanosheets along the zigzag transport direction are nearly 11 times larger than those of them along the armchair transport direction. These results reveal that the thermoelectric properties of porous graphene nanosheets can be well regulated by nitrogen doping, and provide a good theoretical guidance for their application in thermoelectric devices.

Facile Preparations of Electrochemically Exfoliated N-Doped Graphene Nanosheets from Spent Zn-Carbon Primary Batteries Recycled for Supercapacitors Using Natural Sea Water Electrolytes

A single production of nitrogen-doped graphene nanosheets was developed in this present work from a spent Zn-C primary battery. The electrochemically exfoliated nitrogen-doped graphene nanosheets (EC-N-GNS) was applied in supercapacitor symmetric devices. As-prepared EC-N-GNS was utilized for a symmetric supercapacitor with natural seawater multivalent ion electrolyte. The recycling of graphite into nitrogen-doped graphene was characterized by X-ray diffraction and RAMAN spectroscopy. The few-layered morphological structures of EC-N-GNS were analyzed by field emission scanning electron microscope and field emission transmission electron microscope. The electrochemical analysis of the cyclic voltammetry curves observed an electrochemical double-layer capacitor (EDLC) behavior with a potential window of −0.8 V to +0.5 V. The electrochemical galvanostatic charge—discharge study was obtained to be maximum specific capacitance (Csp)—67.69 F/g and 43.07 F/g at a current density of 1 A/g. We promising the facile single-step electrochemically exfoliated EC-N-GNS was obtained from a waste zinc-carbon primary battery to recycle the graphite electrodes. The superior electrochemical performance comparatively bulk graphite and EC-N-GNS for potential energy storage supercapacitor applications.

Effect of nitrogen doping on the structure and electrochemical properties of vertical graphene sheets prepared by HWP-CVD

3D nitrogen-doped vertically-oriented graphene nanosheets (3D N/VGs) were controllably prepared by helicon wave plasma chemical vapor deposition (HWP-CVD) employing argon, methane, and nitrogen by varying the N2 flow rate (RN2) without any catalyst and substrate heating during the growth. The effect of plasma gas phase species on the growth structure of N/VGs thin films was studied. The influence of nitrogen doping content on the structure and properties of VGs was analyzed. A growth model for the preparation of N/VGs by HWP-CVD was proposed. The results show that the elevated doping content of nitrogen atoms promotes enhanced CH4 dissociation and access to more H atoms, leading to an elevated nanosheet number density and a reduced growth rate. More excited N atoms could be embedded into the C vacancy to replace the missing C atom and restore the hexagonal network and increasing the nitrogen content. N/VGs with lower defect densities obtained with enhanced doping of nitrogen. The effective average distance between defects increases with nitrogen content, and the tunneling phenomenon is apparent, increasing resistance. Electrochemical performance tests showed that VGs with high nitrogen atomic content have higher specific capacitance and rate performance, up to 1340 μF/cm2 and 91.7%, respectively.

Ultrasensitive Pressure Sensor Sponge Using Liquid Metal Modulated Nitrogen-Doped Graphene Nanosheets.

Wearable pressure sensors are crucial for real-time monitoring of human activities and biomimetic robot status. Here, the ultrasensitive pressure sensor sponge is prepared by a facile method, realizing ultrasensitive pressure sensing for wearable health monitoring. Since the liquid metal in the sponge-skeleton structure under pressure is conducive to adjust the contact area with nitrogen-doped graphene nanosheets and thus facilitates the charge transfer at the interface, such sensors exhibit a fast response and recovery speed with the response/recovery time 0.41/0.12 s and a comprehensive response range with a sensitivity of up to 476 KPa-1. Notably, the liquid metal-based spongy pressure sensor can accurately monitor the human body's pulse, the pressure on the skin, throat swallowing, and other activities in real time, demonstrating a broad application prospect. Those results provide a convenient and low-cost way to fabricate easily perceptible pressure sensors, expanded the application potential of liquid metal-based composites for future electronic skin development.

Hierarchical three dimensional polyaniline/N‐doped graphene nanocomposite hydrogel for energy storage applications

AbstractWith the rapid development of portable, lightweight, and flexible electronics, the requirement for advanced energy storage systems has arisen that need to be flexible and cost‐effective with higher power/energy densities. In this context, a two‐step approach has been adopted to develop a binder‐free and flexible supercapacitor electrode on carbon cloth based on hierarchical three dimensional (3D) conducting polymer hydrogels. Firstly, nitrogen‐doped graphene (NGN) was synthesized using urea as a reducing as well as a doping agent. Subsequently, polyaniline (PAni) hydrogel has been grown on NGN nanosheets via insitu oxidative polymerization in the vicinity of carbon cloth and further utilized as an electrode for electrochemical measurements. Here, phytic acid was used as a gelatinizer and as a dopant resulting in the formation of a cross‐linked hydrogel structure. The direct deposition of PAni/NGN nanocomposite on carbon cloth strengthens the juncture involving the carbon cloth and electrode material, resulting in enhanced electron transmission. The 3D hydrogel architecture ascertains robust contact between electrolyte and electrode for an efficient charge storage system. For a two‐electrode symmetric arrangement, at 1 A/g, PAni/NGN nanocomposite hydrogel displayed a maximum specific capacitance of 808.7 F/g due to the pseudocapacitive reaction on/near the accessible surface area, as well as an outstanding rate capability and cyclic performance due to electric double layer capacitance (EDLC). The supercapacitor cell delivered maximum specific power and specific energy value of 0.44 kW/kg and 13.63 Wh/kg, respectively. Thus, the composite hydrogel has the benefit of being able to be utilized directly as binder‐free supercapacitor electrodes, leading to viable choice for high‐performance and cost‐effective energy storage devices.

Vanadium carbide and nitrogen-doped graphene nanosheets based layered architecture for electrochemical evaluation of clioquinol detection and energy storage application

Herein, we report the oxidized-vanadium carbide (V8C7Tx) hybridized with nitrogen-doped graphene nanosheets (VC/NG NSs) nanocomposite using hydrothermal followed by sonochemical approach. The oxidized V8C7Tx is shown to be enriched with O-terminated functional groups, which also improves the electrochemical performance of the nanocomposite. Then for the first time, VC/NG NSs nanocomposite is reported as an efficient electrocatalyst for the detection of CQL. The cyclic voltammetry (CV) experiments were performed at the working potential from 0 to 0.7 V (vs. Ag/AgCl). Surprisingly, the nanocomposite's multilayer structure offers a large number of active sites with a high electron transfer rate for CQL detection. The fabricated drug sensor exhibits a lower oxidation potential (0.46 V) and a greater peak current response (12.05 µA) than previously reported sensors. Under optimum circumstances, the fabricated sensors analytically well performed by means of low detection limit (9 nM), wide linear range (0.5–585 µM), and appreciable recovery results (∼98%, (n = 3)) in human urine samples. Furthermore, the nanocomposite shows a high gravimetric capacitance of 235 F g−1 at 1 A g−1 in 1 M KOH, which is the highest value among alkali-based electrolytes for VC based electrodes. Moreover, the nanocomposite demonstrated robust cycling performance even after 8000 cycles with ∼95% capacitance retention. The presence of O-terminated functional groups, various oxidation states of vanadium (+2, +3, and +4), good conducting and catalytic characteristics of N-graphene are worked together to improve electrochemical performance in sensor and energy storage. Thus, the current study offers a promising MXene based nanocomposite material for high-performance electrochemical applications.

Rich and uncovered FeNx atom clusters anchored on nitrogen-doped graphene nanosheets for highly efficient and stable oxygen reduction reaction

It is still challenging but essential to synthesize non-noble catalysts with rich and uncovered catalytic active sites towards oxygen reduction reaction (ORR). And the limited research of the ORR properties of FeNx atom clusters also hinders their practical implementations. Here, we report a two-dimensional (2D) non-precious ORR catalyst constructed by abundant and fully exposed FeNx atom clusters anchored on nitrogen-doped graphene nanosheets (Fe-N-C/NG), which derives from three-dimensional (3D) ZIF-8, 2D graphene oxide nanosheet, and ferrocene. The optimized Fe-N-C/NG delivers outstanding ORR activities (Eonset = 0.97 V, E1/2 = 0.84 V, Jd = 5.48 mA cm−2), excellent Tafel slope (57.7 mV dec−1), remarkable long-term durability, and strong methanol tolerance in an alkaline electrolyte. Its superior catalytic activity is possibly attributed to its unique conversion of nanoarchitecture and the synergistic effects: the change of morphology effectively utilizes the advantages of 2D graphene oxide and 3D ZIF-8, which guarantees sufficient and reachable active sites; the 2D porous nanoarchitecture of Fe-N-C/NG promotes the ion diffusion and mechanical stability; both the FeNx atom clusters and N-doped graphene nanosheets facilitate the catalytic activity. This work introduces an innovative strategy to rationally design the nanoarchitecture and facilely synthesize nonprecious ORR catalysts with sufficient and uncovered active sites for high efficiency and durability.

Fabrication of nitrogen-doped graphene nanosheets anchored with carbon nanotubes for the degradation of tetracycline in saline water

The treatment of wastewater with high salinity is still a challenge because of the quenching effect of various anions on radical processes. The nonradical process may be a more promising pathway. Herein, a 3D structured nitrogen-doped graphene nanosheet anchored with carbon nanotubes (N-GS-CNTs) was prepared by direct pyrolysis of K3Fe(CN)6. The as-prepared catalyst can effectively activate peroxymonosulfate (PMS) for mineralization of tetracycline (TC) over a wide pH range (from 3 to 11) and even in high saline water (500 mM Cl−, HCO3−, etc.). The degradation mechanism was elucidated by both experimental characterizations and DFT calculations. The high catalytic efficiency was attributed to accelerated electron transfer from donor (TC) to acceptor (PMS) in the presence of the catalyst, which acts as electron shuttle mediators to promote a nonradical process. At the same time, the catalyst also enhances the production of singlet oxygen (1O2), hence further increasing the degradation rate. This study not only provides a simple method for synthesizing N-GS-CNT catalysts but also provides new insights into the electron transfer pathway for the removal of organic pollutants under high salinity conditions.

Introduction of nitrogen doped graphene nanosheets as efficient adsorbents for nitrate removal from aqueous samples.

Introducing and developing new kinds of adsorbents are always a significant challenge in water treatments. In this work, for the first time, graphene oxide (GO), nitrogen-doped graphene oxide (ND-GO), highly nitrogen-doped graphene oxide (HND-GO), and 3D high nitrogen-doped graphene oxide (3D-HND-GO) were synthesized and comparatively evaluated in the removal of nitrate content of tap and underground waters. The removal of the target analyte was performed through a batch adsorption approach, and the factors influencing its removal efficiency (i.e., initial pH of the sample, primary concentrations of nitrate, amount of adsorbent, and contact time) were evaluated through a central composite design (CCD) and response surface methodology (RSM). Based on the results, 3D-HND-GO showed the highest removal efficiency in comparison with the other mentioned nanoparticles. The nitrate removal using this adsorbent was modeled successfully so that R 2, adjusted R 2, and predicted R 2 values were 0.9717, 0.9508, and 0.9010, respectively. In addition, the optimal removal condition was achieved using the Nelder-Mead non-linear optimization algorithm as follow: the initial concentrations of nitrate (expressed as nitrogen): 15.0mg/mL, the amount of the adsorbent: 2.0mg/mL; pH of the sample: 3.0; and the contact time: 20.0min. Under this optimal condition, the actual removal result (92.5 ± 4.0%) was in good agreement with the expected value (94.8 ± 5.1%). Additional studies were also performed to comprehensibly evaluate the adsorption activity of the adsorbent (e.g., kinetic, isotherm, and desorption parameters). The adsorption isotherm complied with the Langmuir model illustrating the considerable mono-layer adsorption capacities for the target ions with qm of 8.7mg/g. The adsorption process was indicated to obey a pseudo 2nd order kinetic model, with the rate-limiting step for the adsorption phase. This study revealed which 3D-HND-G leads to improved yield in the nitrate ions elimination, particularly at acidic media, which was related to the enhanced dispersibility and larger surface area. The adsorbent was further successfully used for treating tap and underground water samples. At the present moment, research as grown to modify 3D-HND-G in orders to increase the potentiality for industrial applications. The online version contains supplementary material available at 10.1007/s40201-021-00741-7.

Metal‐organic frameworks derived FeSe 2 @C nanorods interconnected by N‐doped graphene nanosheets as advanced anode materials for Na‐ion batteries

Herein, unique FeSe2@C nanorods interconnected by nitrogen-doped graphene nanosheets (FeSe2@C/NG) were successfully prepared using Fe-based metal-organic framework (MOF) nanorods as sacrificial templates. During the thermal treatment in an inert atmosphere, the FeSe2 nanoparticles were formed in situ when selenium reacted with Fe species in the MOF. The organic species were simultaneously transformed into a conductive carbon material. After combining with N-doped graphene nanosheets, the obtained FeSe2@C/NG composites showed an improved reversible capacity, great rate capabilities, and cycling stability as anodes for sodium-ion batteries. The composite electrode comprised a specific capacity of 411 mA h g−1 after 100 cycles at 0.5 A g−1. When tested at a higher current density of 7.0 A g−1, the discharge capacity was 291 mA h g−1. The improved electrochemical properties can be attributed to structural features of composites and the synergistic effect between the components. The one-dimensional nanostructure of FeSe2@C nanorods can shorten the ion diffusion path. Additionally, the carbon framework derived from the organic species in Fe-MIL-88 and the interconnected N-doped graphene nanosheets imparted a synergistic effect, which led to the formation of a conductive highway that provided a rapid electron transport, an ample ion reaction site, and acted as buffer layers for active materials.

Bottom-up construction of three-dimensional porous MXene/nitrogen-doped graphene architectures as efficient hydrogen evolution electrocatalysts

The exploration of highly-active non-platinum electrocatalysts with low-cost has been regarded as a crucial way to alleviate the major bottleneck in electrocatalytic hydrogen evolution reaction (HER) technology. Herein, we demonstrate the bottom-up construction of three-dimensional (3D) hybrid architectures built from Ti3C2Tx MXene and nitrogen-doped graphene nanosheets (MX/NG) through a facile and cost-effective co-assembly approach. The as-derived MX/NG architectures are endowed with a number of distinctive structural advantages, such as large specific surface areas, 3D cross-linked porous frameworks, ultrathin walls, optimized electronic structures, and good electron conductivity. As a result, exceptional HER performances with a relatively low onset potential, a small Tafel slope, and reliable long-term stability are achieved on the optimized MX/NG electrode, markedly outperforming those of bare Ti3C2Tx and NG electrodes.