Doped Nitrogen Atoms Research Articles

Nitrogen Doping Engineering of V2CTx based Zinc Ion Hybrid Microcapacitors with Quadruple High Energy Density

To accommodate the long-term and stable energy supply requirements for wearable electronics, the reported flexible zinc ion hybrid microcapacitor (ZIHMC) needs to further increase the energy density. So, a nitrogen doped V2CTx (N-V2CTx) based ZIHMC was proposed to achieve high electrochemical performance. The introduction of N heteroatoms by NH3 annealing can dramatically increase the electrical conductivity of V2CTx and simultaneously widen the voltage window to 1.9 V. In detail, the doped nitrogen atoms in V2CTx based device has a maximum capacity of 293.0 mF cm–2, four times higher than that of pure V2CTx based ZIHMC. The mechanism of the enhanced electrochemical performance by nitrogen doped V2CTx was revealed by the experimental analysis and theoretical simulation. And the N-V2CTx based ZIHMC demonstrated high energy density with 150.0 μWh cm–2 at a power density of 380.0 μW cm–2 and excellent stability with 94.80% capacitance retention after 3000 charge-discharge cycles. The N-V2CTx based ZIHMC also presents excellent flexibility without virtually capacity loss after 3000 bending cycles. The good electrochemical performance and flexibility of N-V2CTx ZIHMC make it has potential applications in flexible wearable electronics.

Portable Colorimetric Sensor Array Based on a Porous Single‐Atom Fe Nanozyme with Different Surface Sites for Identifying Artificially Ripened Fruits

AbstractSingle‐atom nanozyme materials have demonstrated exceptional specific catalytic activity due to the atomic‐level dispersion of their active centers. However, the exploration of catalytic mechanisms for single‐atom catalysts is so far limited to the 2D surfaces of nanozymes. In this study, porous single‐atom Fe nanozyme (psaFeN) is successfully prepared through a straightforward coordination‐assisted polymerization‐assembly strategy. The psaFeN composite nanospheres are uniformly sized, exhibiting excellent dispersibility with well‐organized pore channels extending from the center to the surface. Density functional theory calculations reveal that in the psaFeN nanozyme, the (010) facets serve as the primary active surface, where Fe atoms form tri‐coordinated or tetra‐coordinated structures with doped nitrogen atoms. The (100) facets act as auxiliary reactive surfaces with tetra‐coordinated Fe─N as the active center. psaFeN exhibits excellent POD‐like activity (Km = 1.77 mM; Vmax = 173.53 × 10−⁸ M s−1). Given this exceptional bioactivity, a portable colorimetric biosensor is constructed for distinguishing artificially ripened fruits from naturally ripened ones. The sensor achieves precise discrimination with a detection limit as low as 310 nmol L−1. This study is anticipated to offer valuable insights into understanding the 3D catalytic mechanisms of single‐atom nanozymes, promoting their application in the development of robust biosensors for food safety.

Electronic Properties of Monolayer Graphene with Doping of Nitrogen Atom: A Density Functional Theory Study

Abstract As a material that has been widely researched, graphene is certainly interesting because it has many unique features. In its development, graphene is very promising as an optoelectronic material. However, in theory, graphene has obstacles in its development because its band gap position is zero. With various modifications in opening the band gap so that it does not have a value of zero. In the current research, structural modifications were carried out on graphene layers by doping with a number of Nitrogen atoms. The modeling was carried out using graphene with a supercell size of 4 x 4 x 1. Our calculations are based on Density Functional Theory using the PBE – GGA function for potential exchange correlation. The result is the Fermi level shifting and emergence of magnetic moment through doping with Nitrogen atoms. The results obtained certainly open up opportunities for the development of graphene.

Unraveling quantum capacitance of black phosphorene by the doping of non-metals for energy storage applications using DFT method

Supercapacitor plays a pivotal role as energy storage devices in the context of eliminating energy resources. Black Phosphorene (BP) is highly regarded as a potential electrode for supercapacitor (SC) because of its outstanding properties, including excellent carrier mobility and unique electronic properties. In this research work, the monolayer of BP and bilayer of BP (BP/BP) structure is investigated by using DFT. Moreover, the effect of doping and co-doping of non-metal (oxygen, nitrogen) in the mono- and bi-layer was also investigated to increase their performance by modulating the charge storage, and electronic properties of BP. The structural properties, density of states, quantum capacitance, surface charge density, bader charge analysis, isosurface charge density difference, integrated charge density of monolayer and bilayer are studied. The density functional theory (DFT) is used to calculate all above mention properties. DFT-D3 method with Becke-Johnson damping function is used as dispersion correction factor for all the calculations of bilayer. The calculated results find that bilayer structure gives better results as compared to monolayer structure. In this work, results also revealed that doping of oxygen and nitrogen atom significantly enhance the CQ and Q of mono- and bi-layer structure. For aqueous system, all the composites exhibited asymmetrical behavior except BP/BP bilayer. BP-N/BP-N (1369.8µC/cm2), and BP-O/BP-O (-1298.1µC/cm2) bilayer structure are best for anode and cathode material. In case of ionic/organic system, all composites showed asymmetrical behavior. BP-O/BP-O (-6053.5µC/cm2), and BP-N/BP-N (9329.8µC/cm2) bilayer structure is best cathode and anode material.

N-doping of β-ketoenamine based covalent organic frameworks (COFs) for enhancing photocatalytic oxidation activity

β-ketoenamine-based COFs are widely investigated due to their high stability, good crystallinity and tunable skeleton structures. Nitrogen doping is one of the effective ways to enhance the catalytic activity of COFs. Herein, N-doping of β-ketoenamine-based (0N-TP-COF, 1N-TP-COF, 2N-TP-COF) COFs were successfully constructed by the Schiff base condensation reaction between 1,3,5-tiformylphloroglucinol (TP) and p-phenylenediamine containing different numbers of nitrogen atoms. Studies showed that the as-prepared COFs exhibited more suitable electronic structure and more electron-rich active sites with the increasing of N atoms. Furthermore, the photocatalytic performance of 4-formylphenylboronic acid transformation was 0N-TP-COF (99 %, 48 h) < 1N-TP-COF (99 %, 32 h) < 2N-TP-COF (99 %, 16 h), and the photocatalytic performance of benzylamine coupling was 0N-TP-COF (99 %, 16 h) < 1N-TP-COF (99 %, 3.5 h) <2N-TP-COF (99 %, 1.5 h), respectively. Note that all N-doping COFs have excellent catalytic activity as well as stability, and 2N-TP-COF exhibits the highest catalytic activity. This work demonstrates that doping of nitrogen atoms is an effective way to enhance photocatalytic performance.

Prediction of Contact Resistance of 4H–SiC by Machine Learning Using Optical Microscope Images after Laser Doping

In this study, machine learning (ML) was employed to predict the electrical properties of finished devices, specifically focusing on the state of the contacts at the electrodes. The predictions are based on optical microscope images of the surface conditions, which were captured immediately following the laser doping of nitrogen atoms into 4H-SiC. The laser doping process involved varying the laser fluence from 0.4 to 4.0 J/cm2 and using number of laser irradiation to 5, 10, 20, and 100 shots. The ML prediction was carried out in two steps. In STEP1, we classified the contact status into three types.: 1) Schottky junctions (insufficient doping), 2) Ohmic contact (good contact), and 3) Not ohmic (damage caused by laser irradiation). In STEP2, contact resistance prediction (numerical regression) was performed using the dataset predicted as an ohmic contact. As a result, we found that the three classifications in STEP1 could be predicted with a high accuracy of over 88%. Furthermore, the contact resistance prediction in STEP2 could be made with an accuracy (RMSPE: root mean square percent error) of 27.2%. Visualizing the prediction basis of numerical regression using modulus-reweighted grad-regression activation mapping (MoRAM) revealed that the ML model focused on the inside of the laser-irradiated area in the optical microscope image. The results of the scanning electron microscopy observation of the laser-irradiated area showed that ablation and residuals were generated during laser doping in that area. Consequently, it was concluded that our ML model predicted the contact resistance of the finished device taking into consideration these surface conditions. Even highly-skilled laser doping technicians have difficulty predicting the resistance values arising from the ablation and residue conditions. Based on above results, we conclude that our ML model is capable of predicting the electrical characteristics of a finished device, a task that is often considered challenging for humans.

Nitrogen-doped bean-like SiC-based nanofibers for thermal insulation and electromagnetic wave absorption

SiC nanofibers that can be used to absorb electromagnetic wave (EMW) radiation and as thermal insulators simultaneously are highly desirable. In this work, nitrogen-doped bean-like SiC-based nanofibers were prepared by a simple electrospinning and high-temperature pyrolysis in a nitrogen atmosphere, focusing on studying the effects of nitrogen atom doping on the microstructure, EMW absorption, and thermal insulation properties of the fibers. The results showed that nitrogen doping promoted the formation of the SiOxCyNz phase in the fibers, which improved their interfacial thermal resistance and endowed the fibers with extremely low thermal conductivities (∼0.024 W·m−1·K−1 at 25 ℃, 0.092 W·m−1·K−1 at 1000 ℃). Furthermore, the density of carbon defects in the fibers was improved by nitrogen doping, which created numerous new polarization centers and effectively improved the dielectric loss. With a 4 mm thickness, a minimum reflection loss of −51.8 dB was exhibited at 6.3 GHz, indicating that these fibers are highly promising as an absorption material in harsh environments.

Fabrication of monolayer h-BN/LaB6 heterostructure thin film with low work function and high chemical stability

To expand the applications of low work function materials, high chemical stability is necessary to prevent the surface from unfavorable reactions. We developed a 20-nm-thick lanthanum hexaboride (LaB6) thin film covered by a monolayer hexagonal boron nitride (h-BN), which exhibits not only low work function but also high chemical stability. Results demonstrated that the h-BN/LaB6 heterostructure can be formed by vacuum annealing a nitrogen-doped LaB6 thin film. The formation process was investigated using Auger electron spectroscopy (AES), high-resolution electron energy loss spectroscopy (HREELS), and X-ray absorption near edge structure (XANES) spectroscopy. We have elucidated that the doped nitrogen atoms and boron atoms in the film thermally diffuse into the surface during annealing, thereby forming the monolayer h-BN on the surface. Work function was measured using scanning tunneling microscopy (STM). From a practical perspective, chemical stability was evaluated with a heating temperature necessary for restoring the low work function state after air exposure. The work function was comparable to that of the clean LaB6(100) surface. Moreover, it recovered at a much lower temperature than the cleaning temperature of the LaB6(100) surface. We anticipate that this material development will facilitate implementation of the low work function material.

Coupling effect of defects and enriched adsorption sites in bimetal-MOF derived porous carbonaceous anode for high-performance lithium-ion capacitor

Lithium-ion capacitors (LICs) have attracted considerable attention for their ability to combine the high energy characteristics of lithium-ion batteries and the high power densities of supercapacitors. However, the development of LICs still faces critical challenges. Herein, a robust bimetal-MOF derived fluorine and nitrogen co-doped hierarchical porous carbon embedding with Co nanoparticles anode materials (Co@NFC-800) for LICs are developed, which combined with the advantages of amplified interlayer, enriched active sites and improved electrical conductivity. Both theoretically and experimentally results demonstrate that such advantaged structure via fluorine doping to introduce defects and regulate doped nitrogen atom configuration to enrich Li+ adsorption sites and enhance diffusion kinetics synergistically is attempted. Co@NFC-800 deliveres a high reversible capacity and excellent long cycling stability as anode in LIBs, By coupling the Co@NFC-800 anode with commercial activated carbon (AC) cathode, the assembled LICs deliver a high specific energy of 164 Wh kg−1 at 162.9 W kg−1 and maintained to 68.3 Wh kg−1 even at high specific power of 9.1 kW kg−1 as well as long cycling stability (80.2 % over 2000 cycles).The fluorine doping induced both enriched defects and regulable nitrogen atom configuration strategy opens up a new way of carboneous materials for lithium storage.

Nitrogen‐containing microporous carbon with specific morphology for non‐metallic catalytic NO oxidation at room temperature: The effect of morphology and nitrogen doping

AbstractThe optimization of the gas diffusion path and surface coordination environment through morphology control can improve the intrinsic activity of the catalyst in NO oxidation reactions. Microporous nanosheets, nanowires, and spheres of carbon were constructed using resorcinol and formaldehyde as carbon sources, melamine as nitrogen source, and graphene oxide or carbon nanowires as structure‐directing agents to reveal the effects of morphology and nitrogen‐doping on NO oxidation activity at room temperature. With the increase of coating thickness, the ultramicroporous structure becomes pronounced and the nitrogen content increases, which contribute to the improvement of steady‐state NO conversion. The 2D microporous nanosheets (TDC‐200) with sheet structure shows prominent diffusion and adsorption capability than 1D nanowires and sphere, which shortens the gas diffusion path and enhances the efficient utilization of ultramicropores, thereby presenting the highest NO oxidation activity of 78.4% at room temperature. The results of DFT calculations further demonstrate that doping of nitrogen atoms could significantly reduce the (2NO + O2)ads energy barrier and accelerate the reaction. This study provides a deeper understanding of the NO oxidation on non‐metallic catalyst.

Optoelectronic Properties of Nitrogen-Doped Hexagonal Graphene Quantum Dots: A First-Principles Study.

Graphene quantum dots have been widely studied owing to their unique optical, electrical, and optoelectrical properties for various applications in solar devices. Here, we investigate the optoelectronic properties of hexagonal and nitrogen-doped graphene quantum dots using the first-principles method. We find that doping nitrogen atoms to hexagonal graphene quantum dots results in a significant red shift toward the visible light range as compared to that of the pristine graphene quantum dots, and the doped nitrogen atoms also induce a clear signature of anisotropy of the frontier orbitals induced by the electron correlation between the doped nitrogen atoms and their adjacent carbon atoms. Moreover, time-dependent density functional theory calculations with the M06-2X functional and 6-311++G(d,p) basis set reproduce well the experimental absorption spectra reported recently. These results provide us with a novel approach for more systematic investigations on next-generation solar devices with assembled quantum dots to improve their light selectivity as well as efficiency.

Thiourea modulated supercapacitive behavior of reduced graphene oxide

In this report, we investigated the role of the concentration of nitrogen and sulfur containing thiourea in modulating the electrochemical properties of reduced Graphene Oxide (rGO) by controlling the percentage of heteroatoms on the rGO surface. The synthesis route involved the preparation of Graphene Oxide (GO) using an improved method of synthesis in an economical way by reducing the volume of concentrated acids used. Furthermore, GO is reduced by using different mass proportions of thiourea via a simple reflux method. Characterization of the rGO samples by Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDAX) and elemental analysis through CHNS analyzer exhibited successful doping and impact of nitrogen and sulfur atoms on the graphene framework. The comparative electrochemical performance from Cyclic Voltammograms (CV), Galvanostatic Charge Discharge (GCD) profiles and Electrochemical Impedance Spectroscopy (EIS) measurements on the various rGO samples revealed the superiority of 1:8rGO having 15.190 wt% of nitrogen and 26.849 wt% of sulfur and S/N ratio of 1.768, in delivering highest specific capacitance of 465.21 F·g−1 at 1 mV·s−1 scan rate with a remarkable cyclic stability exhibiting a capacitive retention of 119 % and offering lowest charge transfer resistance and diffusion resistance. The study also demonstrated detrimental effect of excess thiourea on electrochemical properties of rGO. This work suggests an effective and simple approach for optimizing the nitrogen and sulfur content in rGO to enhance its electronic properties using thiourea.

Adsorption of tetracycline by nitrogen-enriched biochar prepared at different pyrolysis temperatures: Considering the crucial role of nitrogen configuration

Nitrogen atom doping is widely employed to prepare efficient adsorbents to handle target pollutants thanks to its similarity in radius to carbon atoms and excellent functionality. In this study, three types of nitrogen-enriched biochars (NBCs) were prepared to use the corn straw as the raw material and melamine as the nitrogen source by pyrolyzing at 700, 800, and 900 °C (named 700NBC, 800NBC and 900NBC), which were used to remove tetracycline (TC) from water. Results showed that the 900NBC exhibited the highest specific surface area (324.29 m2/g) as well as the maximum adsorption capacity (194.42 mg/g) for TC, compared to 800NBC (176.44 mg/g) and 700NBC (163.32 mg/g). What’s more, the adsorption kinetics and adsorption isotherms were well-fitted by the pseudo-second-order and Langmuir models, indicating that for the adsorption of TC by NBCs, monolayer adsorption and chemisorption were dominant. Specifically, the excellent adsorption performance of NBCs for TC was mostly attributed to the pore filling, hydrogen bonding, π-π interactions, Lewis acid-base interactions, and electrostatic interactions. Importantly, the graphitic N serves as the primary TC adsorption site, followed by pyridinic N. This study would provide new insight into the impact of nitrogen configuration on the adsorption mechanism of NBCs for TC.

Nitrogen-doped lignin-derived electrode materials for supercapacitors were prepared using the domain-limited effect

Supercapacitors, pivotal in mitigating the energy crisis stemming from dwindling fossil fuel reservoirs, necessitate meticulous consideration of electrode material preparation. While lignin-derived carbon materials sourced sustainably exhibit commendable potential as electrode materials, their intrinsic low capacitance limits widespread utilization. Herein, nitrogen atom doping of lignin (CNL) was accomplished employing a chemical modification technique employing cyanuric chloride as a dopant. The resultant nitrogen content measured at 2.85 %. Subsequent to CNL carbonation, the generated C3N4 was selectively confined to the internal surface of the CNLMS-800 through a domain-limited activation method, thereby rendering it suitable for deployment as a supercapacitor electrode material. CNLMS-800 manifests a substantial specific surface area of 1778.0 m2 g−1 and a concomitantly diminutive pore size of 2.6 nm. Noteworthy, the specific capacitance of CNLMS-800 attains 473.0 F g−1 at a current density of 0.5 A g−1 in a 6 M KOH electrolyte. The resultant energy density reaches 39.0 Wh kg−1 at a power density of 338.0 W kg−1. Crucially, even after 20,000 charge/discharge cycles at a current density of 10 A g−1, the capacitance retention attains an impressive 87.5 % in the KOH electrolyte. This innovative utilization of sustainable resources for electrode fabrication epitomizes a seminal advancement in the field of energy technology.

Synthesis of Carbon Dots from butterfly pea (Cliptoria ternatea) as detection of the heavy metal ion Cu 2+

The synthesis of carbon dots nanomaterials based on butterfly pea (Cliptoria ternatea) with urea doped (N-CDs) has been successfully carried out using the hydrothermal method. The N-CDs material shows a dark brown solution which indicates that the carbon dots have been successfully synthesized. In this study, we analyzed the influence of optical properties before and after adding Cu2+ ions to the sensitivity of N-CD. The characterization of N-CDs was analyzed using a UV-Vis Spectrophotometer and Photoluminescence (PL) Spectroscopy, as well as using Fourier Transform Infra-Red. The research results show that the absorption spectrum range is from 200 to 800 nm, with an absorption peak at 206.58 nm and the band gap energy obtained is 4.95 eV. The CD solution produces good fluorescence when observed under ultraviolet light (395 nm) and emits a turquoise green color. Based on the IR spectrum, there is an increase in transmittance in the carbon dots spectrum after the addition of urea and at the wave number 1404 cm−1 there is a C-N group which indicates that the process of doping nitrogen atoms on the carbon dots has been successful. The sensitivity of N-CD when sensing Cu2+ ions with a minimum Limit of Detection (LOD) is as low as 183.33 nm. The N-CD can be applied as a biosensor friendly and environmentally method.

Simultaneous recycling and nitrogen doping in carbon fiber reinforced plastic using eco-friendly supercritical water treatment for Li-ion batteries anode application

Carbon fiber (CF) is emerging as a high value-added material due to its lightweight nature about 1/4 the weight of steel, coupled with its exceptional strength. In particular, CF reinforced plastic (CFRP), comprising over 60% CF, has gained prominence as a next-generation composite material used in various industries to reduce weight. The widespread use of CFRP has led to a surge in CFRP waste, which arises challenges related to its high cost and waste management, necessitating recycling efforts. However, recycling CFRP is complex because it is composed of thermosetting resins. Conventional recycling methods such as incineration and shredding often result in environmental pollution. Furthermore, during the recycling process, CFs become randomly oriented and primarily repurposed as individual fibers used for reinforcement materials. To address these challenges, our study employs supercritical water for an eco-friendly recycling without the need for catalysts or oxidizers. During this recycling process, we introduced glycine, which simultaneously achieved nitrogen (N) atom doping of the recycled CF. This dual approach resulted in the production of recycled CFs doped with N atoms. These doped and recycled CFs were reused as anode materials for lithium-ion batteries and exhibited a capacity of approximately 340 mAh g−1 (at 0.1C) and a stable cycling lifespan over 150 cycles (at 1C). This promising performance suggests their potential as replacements for traditional graphite anode materials.

Pre-implanting metal oxides to endow the N-doped carbon with boosted bifunctional catalytic activities towards oxygen reduction and oxygen evolution reactions

Nitrogen-doped carbon-based materials exhibit promising prospect as the catalysts to oxygen reduction reaction (ORR). Incorporating transition metal oxides with the catalysts can endow them with oxygen evolution reaction (OER) activity to construct bifunctional catalysts for rechargeable zinc-air batteries. In this work, a catalyst (named as 300NiFe-Mi-C) was prepared by a metal oxide-implanting strategy. The mixed metal salts of Ni and Fe were first heated to produce metal oxides, and then blended with 2-methylimidazole and carbon black, and subsequently pyrolyzed at a high temperature. In the pyrolysis, a part of metal oxides was reduced to metallic state to facilitate the doping of nitrogen atoms into carbon to form the ORR active sites while a part of metal oxides was retained to afford OER activity. Benefiting from the pre-implanting strategy of metal oxides, the resultant 300NiFe-Mi-C presents enhanced OER performance with 1.56 V of OER potential at 10 mA cm−2, outperforming the 1.68 V of the controlled sample NiFe-Mi-C (without pre-implanting) and 1.70 V of RuO2. The 0.83 V of ORR half-wave potential of 300NiFe-Mi-C is also comparable to the 0.82 V of NiFe-Mi-C and 0.86 V of Pt/C, revealing satisfactory bifunctional catalytic activities. The rechargeable zinc-air battery equipped with 300NiFe-Mi-C can stably operate at ∼1.25 V with 10 mA cm−2, being higher than ∼1.21 V of Pt/C+RuO2. The battery also presents outstanding durability and rechargeability, demonstrating the bifunctional activities of 300NiFe-Mi-C can be realized in practical applications.

Extrinsic defects-rich biochar for efficient peroxydisulfate activation: Electronic structure modulation and disparate nonradical mechanisms

Doping nitrogen atoms into carbon materials will produce abundant extrinsic defects, which can significantly improve the catalytic activity toward water remediation. However, there is still a lack of systematic research on which extrinsic defect is the real active site and how extrinsic defects enhance the catalytic activity of carbon materials. In this work, the sludge derived biochar with different configuration of extrinsic defects (pyrrolic-N, pyridinic-N, and graphitic-N.) were successfully synthesized by controlling nitrogen doping amount. The adsorption experiments showed that the biochar with rich graphitic-N significantly enhanced the adsorption ability of peroxydisulfate (PDS), which further led to the excellent catalytic activity toward norfloxacin (NOR) degradation, with 91 % removal efficiency within 90 min. The pseudo-first-order degradation rate constant (Kobs) was strongly positively correlated with the content of graphitic-N. Electron paramagnetic resonance (EPR) analysis and quenching experiments revealed that metastable reactive species (PDS*) were the dominated reactive species in NBC/PDS system. Besides, density functional theory (DFT) calculations demonstrated that the existence of graphitic-N most effectively improved the charge transfer among biochar, PDS and NOR compared to pyrrolic-N and pyridinic-N. Electrochemical characterization and Raman results further identified that graphitic-N heightened the direct electron transfer rate due to the formation of PDS*. The Fukui function predicted the reactive sites of NOR. All of these led to the high NOR removal efficiency. This study provided new insights for the design of non-metallic biochar catalysts with rich extrinsic defects for effectively activating PDS to degrade fluoroquinolone antibiotics.

Screening of Transition Metal Supported on Black Phosphorus as Electrocatalysts for CO2 Reduction.

The electrocatalytic CO2 reduction (CO2RR) is an effective and economical strategy to eliminate CO2 through conversion into value-added chemicals and fuels. However, exploring and screening suitable 2D material-based single-atom catalysts (SACs) for CO2 reduction are still a great challenge. In this study, 27 (3d, 4d, and 5d, except Tc and Hg) transition metal (TM) atom-doped black phosphorus (TM@BP) electrocatalysts were systematically investigated for CO2RR by density functional theory calculations. According to the stability of SACs and their effectiveness in activating the CO2 molecule, three promising catalysts, Zr@BP, Nb@BP, and Ru@BP, were successfully screened out, exhibiting outstanding catalytic activity for the production of carbon monoxide (CO), methyl alcohol (CH3OH), and methane (CH4) with limiting potentials of -0.79, -0.49, and -0.60 V, respectively. A catalytic relationship between the d-band centers of SACs and the limiting potential of CO2RR was used to estimate the catalytic activity of catalysts. Furthermore, Nb@BP has high selectivity for CO2RR to CH3OH compared to H2 formation, while the hydrogen evolution reaction significantly impacts the synthesis of CO and CH4 on Zr@BP and Ru@BP. Nitrogen atom doping in BP is beneficial for enhancing the selectivity of CO2RR, but it is detrimental to the activity of CO2RR. This study offers theoretical guidance for synthesizing highly efficient CO2RR electrocatalysts and further enhances structural modulation methods for layered 2D materials.

Nitrogen-doped coal-based microporous carbon material co-activated by HCOOK and urea for high performance supercapacitors

The doping of heteroatoms can adjust the surface chemical state of porous carbons, which is conducive to improving the surface activity, and enhancing the hydrophicity and conductivity of carbon electrodes. Herein, we developed a facile and green strategy to obtain nitrogen-doped coal-derived porous carbon dominated by micropores for high performance supercapacitor. The hydrothermal treatment of coal and urea can not only achieve the doping of nitrogen atoms, but also conducive to the subsequent activation process. Benefiting from the large micropore volume and specific surface area (0.68 cm3 g−1 and 1563 m2 g−1), suitable micropore size, and high content of surface CO, N-Q and N-5, the optimal sample exhibits a large capacitance of 371 F g−1 (1 A g−1), high capacitance retention of 67% (50 A g−1), and outstanding cyclic durability in a three-electrode system (aqueous electrolyte). Furthermore, the symmetrical supercapacitor in neat EMIM BF4 shows a high energy density of 40 Wh kg−1 (625 W kg−1). This work proposes a facile and potential strategy for preparing nitrogen-doped porous carbon materials with outstanding electrochemical property for supercapacitors and provides a novel insight for the efficient and low carbonization utilization of coal resources.