Heteroatom Co-doping Research Articles

Plasmonic Ag-nanoparticles decorated phosphorus and boron co-doped g-C3N4 for enhanced photocatalytic H2 production

Solar water splitting by semiconductor photocatalysts has emerged as a favorable approach for green hydrogen production. Graphitic carbon nitride (g-C3N4) has gained substantial recognition amongst numerous semiconductor photocatalysts as a metal-free semiconductor with suitable band gap, appropriate band edge positions, and satisfactory photocatalytic activity for hydrogen production. However, its practical application is severely affected by high charge carrier recombination rate and inefficient visible light absorption. Introducing non-metal dopants into the g-C3N4 structure could suppress charge carrier recombination and tune the electronic property. Also, metal nanoparticles exhibit surface plasmon resonance (SPR) upon light interaction increasing the visible light absorption by the transport of hot electrons into the g-C3N4 framework. In this work, we report hybrid photocatalytic materials containing Ag-plasmonic metal and non-metal (B/P) dual heteroatom-doped g-C3N4 prepared via in-situ thermal polycondensation and succeeded by the photodeposition of Ag NPs. The structure of the prepared materials was studied through PXRD and FTIR spectroscopy; XPS was used for chemical analysis; SEM was used to study the morphology; and optical characteristics were studied through UV–Vis and PL spectroscopic techniques. The synergistic effects of SPR and heteroatom co-doping exhibit superior photocatalytic hydrogen production compared to pristine, B or P individual-doped, and B/P co-doped g-C3N4 samples. The optimized 1Ag/PBCN photocatalyst has demonstrated the highest photocatalytic hydrogen production rate of 1825 μmolh-1g−1, 18.3 times greater than g-C3N4. The modified hybrid material shows better activity due to the efficient charge carriers separation and extended visible light absorption. This work indicates that elemental co-doping and loading plasmonic nanoparticles on g-C3N4 to form hybrid nanocomposites may be a potential strategy to achieve better photocatalytic hydrogen evolution. The proposed methodology and outcomes will be helpful in the design and development of plasmon-enhanced hybrid photocatalysts for solar-driven green hydrogen production from water splitting.

Preparation of biomass-based N, P, and S co-doped porous carbon with high mesoporosity based on the synergistic effect of NaOH/thiourea and melamine phosphate and its application in high performance supercapacitors

Biomass-based interconnected porous carbon is not only inexpensive and eco-friendly, but also has the characteristics of a large specific surface area and multiple heteroatom co-doping, making it prominent in the energy storage device field. This work reports a simple method to fabricate N, P, and S co-doped interconnected porous carbon from bamboo pulp fiber by one-step pyrolysis method with NaOH/thiourea aqueous and melamine phosphate. In this reaction system, NaOH/thiourea is an activator and a solvent for bamboo pulp fiber, thiourea is the dopant of nitrogen and sulfur, and melamine phosphate is the dopant of nitrogen and phosphorus. The synergistic effect of NaOH/thiourea and melamine phosphate under freezing conditions contributed to increasing the specific surface area, mesoporosity, degree of graphitization, and heteroatom doping of porous carbon, thereby improving its electrochemical behavior. The synthesized porous carbon exhibits interconnected loose structure, huge specific surface area, extremely high mesoporosity (98.26%) and N (3.78 at%), P (0.32 at%), and S (3.36 at%) co-doping characteristics. As a supercapacitor electrode, it presents a specific capacitance (316 F⋅g−1) at a current density of 1 A⋅g−1. After assembly into a symmetrical supercapacitor, it has a high energy density (16.3 Wh⋅kg−1) at a power density of 489.0 W⋅kg−1, and an excellent cycling stability (91.2% capacitance retention after 5 000 cycles in 6 M KOH). In addition, this work aims to find a novel sustainable approach of using renewable biomass to produce high performance electrode materials to meet the need of different energy storage applications.

First-principles study of the structural and electronic properties of BN-ring doped graphene

Since advanced silicon-based device components are moderately chemically tunable, doped graphene has emerged as a promising candidate to replace this semiconducting material in flexible miniaturized electronic devices. Indeed, heteroatom codoping (i.e., with boron and/or nitrogen) is an appealing strategy to tune both its structural and electronic properties, possibly inducing a band gap in graphene. However, presently synthesized BN-doped carbon-based materials are randomly doped, leading their electronic properties not to be reproducible. Using first-principles techniques, the present study investigates the periodic doping of graphene with borazine-like rings in order to search for an entirely new class of BNC hybrid 2D materials exhibiting high stabilities and optimized band gaps for optoelectronic applications. Ab initio calculations show that BN-ring doped graphene displays cohesive energies comparable with benchmark ideal periodic BNC systems (such as ${\mathrm{BC}}_{3}$ and ${\mathrm{BC}}_{2}\mathrm{N}$) with a decreasing linear trend toward high concentrations of BN rings. Band gaps of BN-ring doped graphene systems are calculated using many-body perturbation techniques and are found to be sensitive to the doping pattern and to be considerably larger for high concentration of BN rings exhibiting the same orientation. These predictions suggest that BN-ring doped graphene materials could be interesting candidates for the next generation of optoelectronic devices and open new opportunities for their synthesis using chemical bottom-up approaches.

A novel one-step method to prepare N, S Co-doped sub-fluorinated carbon electrode materials for ultrahigh-rate lithium-fluorinated carbon battery

To improve the electrochemical performance of fluorinated carbon (CFx) for lithium-fluorinated carbon batteries, the nitrogen and sulfur co-doped sub-fluorinated carbon cathode material (NS-sCFx) is synthesized by a one-step method of heteroatom doping and defluorination. Experimental results confirm that nitrogen and sulfur elements are successfully doped on the surface of CFx material, and the surface fluorinated degree is reduced. DFT calculations and experimental results demonstrate that the heteroatoms co-doping and defluorination can generate a conductive interface, increase activation sites, and induce charge redistribution, producing a superior transfer rate of electrons and lithium ions. Hence, the NS-sCFx cathode material possesses excellent electrochemical properties, large specific capacity, high-rate performance, high power density, and no initial voltage delay. The Li/NS-sCFx battery delivers a specific capacity of 590.4 mAh·g−1 with a voltage plateau of 1.997 V at 20 C without initial voltage delay, corresponding to a power density is 35946 W kg−1. Extraordinarily, an ultra-high power density of up to 107100 W kg−1 at 70 C is achieved without significantly initial voltage delay. This study reveals the functional mechanism of NS-co-doping and defluorination to improve the electrochemical performance of NS-sCFx material, which can be used as a reference for the design and development of related electrode materials.

Enhanced photocatalytic hydrogen evolution under visible-light using C, N co-doped mesoporous TiO2 nanocrystals templated by ionic liquids

Introducing heteroatoms into TiO2 photocatalysts is an effective way to improve its visible-light driven photocatalytic performance. However, the strategies to realize it always require hazardous reagents and/or high temperature. Herein, we put forward a facile and environmentally benign strategy for synthesizing C, N co-doped mesoporous TiO2 nanocrystals. The preparation consists of microwave heating of a simple mixture of H2O, imidazolium-based ionic liquid (IL) and tetrabutyl titanate and subsequent heat-treatment. During the synthesis, the IL acts as reaction solvent, microwave absorbent, C and N sources, and structure-directing agent. Such a strategy not only simplifies the synthesis by avoiding the employment of additional reactants and structure-directing agents towards constructing TiO2 with small sizes, well-developed mesoporous structure and abundant C, N dopants in the lattices, but also lows down the post-processing temperature, which can relieve the secondary growth of TiO2 grains. Benefiting from the mesoporous structure and heteroatom co-doping, the synthesized material shows high specific-surface area, excellent hydrophilicity, elevated valence-band edges, abundant defect levels and narrowed band-gap, which contribute to the improved visible-light absorption, reduced photogenerated electron-hole recombination, and rapid charge transfer and surface-catalyzed reactions. As a result, the material exhibits higher photocatalytic H2 generation performance under the visible-light irradiation than many conventional types of doped TiO2. Besides, the formation mechanism of this TiO2 and the relationships of IL with the morphology and co-doping process have been revealed. This work highlights great potential of IL-assisted microwave synthesis in developing heteroatoms co-doped TiO2 with enhanced photoactivity and application in the solar energy conversion.

Yolk-shell-structured SiO2@N, P co-doped carbon spheres as highly stable anode materials for lithium ion batteries

Silicon-based materials have attracted great interest as potential candidates for graphite anodes owing to their extremely high specific capacity and low working potential. Nevertheless, the conventional application of silicon-based anode materials is seriously limited by their poor electrical conductivity and severe volume change. Herein, the development of high-performance anode materials for lithium ion batteries (LIBs) is demonstrated using yolk-shell-structured SiO2@N, P co-doped carbon spheres (SiO2@NPC Y.S.) with an optimized yolk size. The highly controlled structure with sufficient void spaces between the yolk and shell can effectively alleviate the volume swelling of SiO2, thereby improving the long cyclability during repeated lithiation/delithiation. Furthermore, N, P co-doped carbon shells can not only improve the electrical conductivity but also encourage the expansion of the interlayer distance of carbon, which is favorable for both Li + storage and rate performance. SiO2@NPC Y.S. shows a high capacity retention of 94.3% and reversible specific capacity of 705 mAh g−1 over 300 cycles at a current density of 0.1 A g−1. This work would pave the way for the design of anode materials of LIBs with highly controlled yolk-shell structures and heteroatom co-doping.

Electronic and Optical Properties of Twin T-Graphene Co-Doped with Boron and Phosphorus.

Twin T-graphene (TTG) is a new two-dimensional carbon allotrope of graphene. Heteroatom co-doping is an effective method for the modulation of the physical and chemical properties of two-dimensional materials. This study explored the structural stability, electronic structures, and optical properties of boron and phosphorus co-doped TTG using first-principles calculations. TTG was doped with B and P atoms (BP) at different positions considering 13 different configurations. Pristine TTG has a band gap of 1.89 eV, and all BP co-doped TTG (TTG/BP) systems remain semiconducting with band gaps that gradually decrease with increasing doping concentration. For a given doping concentration, the TTG/BP-ortho systems had a narrower band gap than the corresponding TTG/BP-para systems. The TTG and TTG/BP systems exhibited significant optical anisotropy. In the infrared region, BP co-doping increased the absorption coefficient, and the reflectance and refractive index increased with increasing doping concentration, except for the vertical component of the TTG/BP-ortho system. In the visible region, the absorption coefficient, reflectance, and refractive index decreased with increasing doping concentration for the vertical component, and the peaks were red-shifted from the near-ultraviolet region to the visible region. In the near-ultraviolet region, the reflectance also decreased with increasing doping concentration. The BP co-doping concentration can regulate the electronic structures and optical properties of the TTG, showing that the BP co-doped TTG has potential for application in nanoelectronics and optoelectronics.

Conjugated microporous polymer derived N, O and S co-doped sheet-like carbon materials as anode materials for high-performance lithium-ion batteries

Rational design and preparation of nitrogen (N), oxygen (O), and sulfur (S) co-doped materials with distinguished electrochemical performance in lithium-ion batteries are highly sensible. In this study, layered structure carbon material (PTPAO@600) with co-doped N, O and S elements is prepared by carbonizing conjugated microporous polymers (CMPs) as a precursor. When PTPAO@600 electrode material employed as anode of LIBs, and evaluated its properties in electrochemical aspects. After cycling for 800 times under 0.1 A g−1, PTPAO@600 electrode has shown powerful reversible specific capacity of 1142.5 mAh g−1, and excellent rate capability of 275 mAh g−1 at 2.0 A g−1 large current density. Long-cycle performance for 1000 charge/discharge cycles shows that the capacity is retained at 490.9 mAh g−1 under 1.0 A g−1, revealing its high stability. Such high lithium storage performance is mainly attributed to rich heteroatom co-doping, larger specific surface area and high Li+ diffusion coefficient. The superior electrochemical performance makes the PTPAO@600 a anode material with potential in secondary batteries.

Ultrasensitive Boron-Nitrogen-Codoped CVD Graphene-Derived NO2 Gas Sensor.

Recent trends in 2D materials like graphene are focused on heteroatom doping in a hexagonal honeycomb lattice to tailor the desired properties for various lightweight atomic thin-layer derived portable devices, particularly in the field of gas sensors. To design such gas sensors, it is important to either discover new materials with enhanced properties or tailor the properties of existing materials via doping. Herein, we exploit the concept of codoping of heteroatoms in graphene for more improvements in gas sensing properties and demonstrate a boron- and nitrogen-codoped bilayer graphene-derived gas sensor for enhanced nitrogen dioxide (NO2) gas sensing applications, which may possibly be another alternative for an efficient sensing device. A well-known method of low-pressure chemical vapor deposition (LPCVD) is employed for synthesizing the boron- and nitrogen-codoped bilayer graphene (BNGr). To validate the successful synthesis of BNGr, the Raman, XPS, and FESEM characterization techniques were performed. The Raman spectroscopy results validate the synthesis of graphene nanosheets, and moreover, the FESEM and XPS characterization confirms the codoping of nitrogen and boron in the graphene matrix. The gas sensing device was fabricated on a Si/SiO2 substrate with prepatterned gold electrodes. The proposed BNGr sensor unveils an ultrasensitive nature for NO2 at room temperature. A plausible NO2 gas sensing mechanism is explored via a comparative study of the experimental results through the density functional theory (DFT) calculations of the adsorbed gas molecules on doped heteroatom sites. Henceforth, the obtained results of NO2 sensing with the BNGr gas sensor offer new prospects for designing next-generation lightweight and ultrasensitive gas sensing devices.

Phytic acid-induced self-assembled chitosan gel-derived N, P–co-doped porous carbon for high-performance CO2 capture and supercapacitor

Heteroatom-doped porous carbon materials (HPCMs) have attracted great attention due to their excellent physical and chemical properties and the enhanced performance of multiple heteroatom co-doping. Herein, N, P-co-doped porous carbon materials (NPPCs) are developed via a novel synthesis of the phytic acid-induced self-assembled chitosan aerogel followed by pyrolysis and activation. Phytic acid serves as a P source, acid regulator and structure-directing agent for improved activation efficiency to create more pores. A little of NaNO 3 is used both as a template and activator simultaneously. The porosity and N content of such NPPCs are controlled by rationally tuning the pyrolysis temperature and the mount of NaNO 3 . The NPPC-0.75-600 delivers a good CO 2 adsorption capability of 3.02 and 5.31 mmol g −1 at 100 and 500 kPa, respectively, and has an excellent stability with almost no adsorption capacity decay even after successive 20 cycles. For supercapacitors (SCs), the NPPC-0.75-700 also displays a high capacitance of 231.2 F g −1 at 1 A g −1 and an outstanding stability at circa 96.7% initial capacity after 10000 cycles. These results highlight the great potential of such NPPCs in CO 2 capture and SCs, and the novel synthetical route offers new insights for the readily scalable production of HPCMs. • Phytic acid induced chitosan gel and served as a P source and activation agent. • N,P-co-doped porous carbon delivered a CO 2 capture ability of 5.31 mmol g −1 at 298 K. • N,P-co-doped porous carbon exhibited specific capacitance at 231.2 F g −1 at 1 A g −1 . • CO 2 capture and supercapacitor performances were substantially improved by P doping.

S and P Dual-Doped Carbon Nanospheres as Anode Material for High Rate Performance Sodium-Ion Batteries

The heteroatom doping of carbon materials can significantly improve the electrochemical performance of sodium-ion batteries. However, conventional doping techniques involve more than two steps, making them unsuitable for scale-up. In this study, an S and P co-doped carbon material is synthesized using a simple, one-step plasma-in-liquid process. The synthesized material consists of abundant macropores, which can improve the electrochemical properties of sodium-ion batteries. When the synthesized anode material is applied to a sodium-ion half-cell, the cell exhibits a remarkable cycling life of 3000 cycles at a high current density of 10 A g−1, with a high reversible capacity over 125 mAh g−1. These results indicate that S and P co-doped carbon materials are promising candidates as anodes for sodium-ion batteries, and the plasma-in-liquid process is an effective strategy for heteroatom co-doping.

Surface Engineering of Carbon via Coupled Porosity Tuning and Heteroatom‐Doping for High‐Performance Flexible Fibrous Supercapacitors

AbstractFlexible fibrous supercapacitors (FFS) are considered the next‐generation wearable energy storage devices because they provide reliable safety, eco‐friendliness, and high power density. In particular, the FFS is desirable for application to wearable electronics because it can overcome disadvantages of the lithium‐ion battery (LIB), such as the hazard of explosion and the complex manufacturing process. Nevertheless, the practical application of the FFS continues to be inhibited by the poor energy storage performance due to the limited specific surface area, poor electrical properties, and low wettability of the carbon fiber electrode. Herein, for the first time, the surface engineering of an FFS using nitrogen and fluorine codoped mesoporous carbon fibers (FFS‐NFMCF) is described, and the synergistic effect of porosity tuning and heteroatom codoping upon the electrochemical performance is demonstrated. The resultant supercapacitor shows a high specific capacitance of 243.9 mF cm−2 at a current density of 10.0 µA cm−2 and good ultrafast cycling stability with capacitance retention of 91.3% for up to 10 000 cycles at a current density of 250.0 µA cm−2. More interestingly, the FFS‐NFMCF exhibits good mechanical properties and remarkable safety in practical application, thus demonstrating its feasibility for use in wearable electronic textiles.

Si doped Fe-N/C catalyst for oxygen reduction reaction directed by ordered mesoporous silica nanospheres template strategy

Template-assisted synthesis strategy is an effective approach to prepare high performance oxygen reduction catalyst. The Fe-N/C catalysts were prepared via high temperature pyrolysis of the composites containing Fe-loaded mesoporous silica nanospheres and polypyrrole wrapped on it (Fe/mSiO2@PPY). Fe loading ways combined with polymerization means of pyrrole greatly influence the structure and morphology of the final catalysts. By controlling the type of templates (mesoporous, microporous and nonporous templates) and synthesis conditions, Si doped Fe-N/C (Si-Fe-N/C) catalyst with hollow shell structures was obtained. The multiple heteroatom co-doping of Si, Fe and N in carbon framework are confirmed by EDS, XPS and Raman. The co-doping of Fe and N increases the oxygen reduction reaction (ORR) catalytic activities, while the doping of Si facilitates graphitization degree of carbon framework. The electrochemical performance of the Si-Fe-N/C catalyst was evaluated by the linear sweep voltammograms (LSV). It exhibits higher current density (5.4 mA cm−2) and more positive half-wave potential (0.83 V vs. RHE), which is comparable to commercial Pt/C catalyst. Stability tests show that the Si-Fe-N/C catalyst possesses excellent durability and more than 90% of its original activity can be retained after 50,000 s running at 0.68 V (vs. RHE).

Enhancing the reactivity of carbon-nanotube for carbon monoxide detection by mono- and co-doping of boron and nitrogen heteroatoms: A DFT and TD-DFT study

Carbon nanotube (CNT) doped with boron (p-type) and nitrogen (n-type) atoms (BxNy@CNT) have attracted the attention of many experimental and theoretical researchers for variety of industrial applications such as catalytic processes in fuel cells and detection of environmental pollutants. BxNy@CNTs can be synthesized with different concentrations (i.e. x/y ratios) and various configurations (i.e. relative position of B to N atoms), and therefore, BxNy@CNTs show an unpredictable reactivity in physical and chemical reactions. Hence, the selection of an appropriate BxNy@CNTs combination to achieve the most efficiency for a specific application is a challenge for experimentalists. In this regard, herein, we investigated theoretically different combinations of BxNy@CNT (x, y = 0, 1), i.e. single doped boron (B@CNT) and nitrogen (N@CNT) along with multi-doped boron and nitrogen BN@CNT, in three ortho, meta and para-BN@CNT configurations for detection and removing of monoxide carbon (CO) as a diatomic toxic gas. Theoretical calculations were done based on the quantum calculations in DFT and TD-DFT levels of theory using M06-2X (and B3LYP-D3)/6-31+G(d,p) functional/basis set. We focused on variations in electrical (useable for electronic based nano-sensor devices) and optical (useable for optical based nano-sensor devices) properties after adsorption of CO gas. Results indicate that, compared to the other combinations, co-doping of boron in para position relative to nitrogen (para-BN@CNT) can significantly activate the inert-CNT toward CO sensing. Theoretical results of this work can help experimental scientists in the synthesis and selection of the appropriate BxNy@CNT combinations for applying in nanotube based nano-sensors.

Thermally Driven Amorphous‐Crystalline Phase Transition of Carbonized Polymer Dots for Multicolor Room‐Temperature Phosphorescence

AbstractMulticolor carbon dot (CD)‐based nanomaterials offer a variety of opportunities for potential applications in bioimaging, optoelectronic devices, and information security. However, it still remains a challenge to modulate the conjugated π‐structure of CDs to achieve multicolor room‐temperature phosphorescence (RTP). Herein, the authors present a strategy based on thermally driven amorphous−crystalline phase transition to achieve multicolor carbonized polymer dots (CPDs) with the emission color tunable from green to orange‐red. This is the first report on multicolor RTP emission from CDs by means of thermal stimulus. Further investigations reveal that the formation of self‐protective covalently crosslinked frameworks and codoping of multiple heteroatoms play a crucial role in the production of RTP. RTP color tunability can be attributed to different crystalline contents of the conjugated π‐domain within CPDs. Potential application of the developed CPDs as printable and writable security inks for advanced multilevel anti‐counterfeiting and encryption is demonstrated. This work paves a path for the development of multicolor RTP materials and suggests great potential of CDs in exploiting novel optical materials toward intriguing applications.

From onion skin waste to multi-heteroatom self-doped highly wrinkled porous carbon nanosheets for high-performance supercapacitor device

Herein, we report the synthesis of N, S, P-self-doped porous and wrinkled graphene-like carbon nanosheets derived from the abundant waste onion skin via carbonization and activation strategy. The optimized onion skin derived carbon (OnC-900) exhibits highly wrinkled graphene-like morphology and multi-heteroatom doping without any external dopants is confirmed via field emission scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The OnC-900, acting as a supercapacitor electrode, exhibits excellent specific capacitance of 478 F g−1 at a current density of 1 A g−1 and maintains 241.7 F g−1 even at 6.7 A g−1 in the three-electrode cell indicating its excellent rate capability. The assembled symmetric supercapacitor device using aqueous neutral electrolyte (1 M Na2SO4) delivers outstanding specific energy of 17 Wh kg−1 with a wide potential window up to 1.4 V. The device also exhibits excellent cyclic stability by retaining 93% of initial capacitance over 10,000 cycles at a current density of 3 A g−1. This enhanced performance of the electrode is mainly due to the high specific surface area and the heteroatom co-doping that provides improved surface wettability by polarized surface, induced pseudocapacitance effect, and improved electronic conductivity. These results demonstrate that onion waste derived multi-heteroatom co-doped graphene-like carbon nanosheets have great potential for renewable and sustainable energy storage devices.

The kinetics investigation of nitrogen/sulfur co-doped reduced graphene oxide@spinel SnFe2O4/Sn0.205Fe1.727O3 as high performance anode for lithium-ion batteries and its application in full cells

A novel N/S co-doped reduced graphene oxide (rGO) composited with spinel SnFe2O4/Sn0.205Fe1.727O3 (NSG@SFO) is synthesized as a new anode for Lithium ion batteris (LIBs). The NSG@SFO anode showed a remarkably high charge/discharge capacity of 527/529 mAh g−1 after 1000 cycles at 6 A g−1 in half-cell and a high charge capacity of 430 mAh g−1 after 100 cycles at 1.4 A g−1 in full-cell configurations. The excellent performance of NSG@SFO is due to the heteroatom co-doping of N and S on reduced graphene oxide can enhance the electronic conductivity, control huge volume expansion/contraction and maintain the structural stability of SFO. The kinetics investigation indicates that the combination of N/S co-doped rGO with SFO exhibited high surface pseudocapacitive behavior and possesses lower activation energies both for the Li-ion transfer in the solid electrolyte interphase film and the charge transfer in the material than pure SFO. Such intrinsic quality makes NSG@SFO composites promising anode material for high performance LIBs.

Recent advances in heteroatom-doped graphene quantum dots for sensing applications.

Graphene quantum dots (GQDs) are carbon-based fluorescent nanomaterials having various applications due to attractive properties. But the low photoluminescence (PL) yield and monochromatic PL behavior of GQDs put limitations on their real-time applications. Therefore, heteroatom doping of GQDs is recognized as the best approach to modify the optical as well as electronic properties of GQDs by modifying their chemical composition and electronic structure. In this review, the new strategies for preparing the heteroatom (N, B, S, P) doped GQDs by using different precursors and methods are discussed in detail. The particle size, emission wavelength, PL emissive color, and quantum yield of recently developed heteroatom doped GQDs are reported in this article. The investigation of structure, crystalline nature, and composition of heteroatom doped GQDs by various characterization techniques such as high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) are also described. The recent progress on the impact of mono or co-doping of heteroatoms on PL behavior, and optical, electrochemiluminescence (ECL), and electrochemical properties of GQDs is also surveyed. Further, heteroatom doped GQDs with attractive properties used in sensing of various metal ions, biomolecules, small organic molecules, etc. by using various techniques with different limits of detection are also summarized. This review provides progressive trends in the development of heteroatom doped GQDs and their various applications.

Graphene-carbon 2D heterostructures with hierarchically-porous P,N-doped layered architecture for capacitive deionization.

Exploring a new-family of carbon-based desalinators to optimize their performances beyond the current commercial benchmark is of significance for the development of practically useful capacitive deionization (CDI) materials. Here, we have fabricated a hierarchically porous N,P-doped carbon–graphene 2D heterostructure (denoted NPC/rGO) by using metal–organic framework (MOF)-nanoparticle-driven assembly on graphene oxide (GO) nanosheets followed by stepwise pyrolysis and phosphorization procedures. The resulting NPC/rGO-based CDI desalinator exhibits ultrahigh deionization performance with a salt adsorption capacity of 39.34 mg g−1 in a 1000 mg L−1 NaCl solution at 1.2 V over 30 min with good cycling stability over 50 cycles. The excellent performance is attributed to the high specific surface area, high conductivity, favorable meso-/microporous structure together with nitrogen and phosphorus heteroatom co-doping, all of which are beneficial for the accommodation of ions and charge transport during the CDI process. More importantly, NPC/rGO exhibits a state-of-the-art CDI performance compared to the commercial benchmark and most of the previously reported carbon materials, highlighting the significance of the MOF nanoparticle-driven assembly strategy and graphene–carbon 2D heterostructures for CDI applications.

Upcycling discarded duck down into highly porous and nitrogen/oxygen dually doped graphitic carbon for admirable energy and CO2 storage

The convenient fabrication of heteroatom self-doped porous carbons from various biomasses has become a hot topic due to their unique advantages in environmental and energy-related applications. In this study, N/O self-doped and sheet-like graphitic porous carbons were successfully prepared by straightforward catalytic activation of recycled duck down with mixed ZnCl2-FeCl3 salts. During the synthesis, FeCl3 exerts impressive influence on the microstructure of the derived carbons. The obtained porous carbon can deliver an impressive gravimetric capacitance of 222 F g−1 along with powerful retention rate of 80% up to 10 A g−1, as well as all-right capacity preservation of 109% after 5,000 cycles, owing to the favorable textural structure with readily accessible active surface area, rapid electrolyte transport channels, moderate graphitization level, and advantageous surface chemistry of rich heteroatoms co-doping. Additionally, the as-synthesized carbons also exhibit superior CO2 uptake capacity up to 4.4 mmol g−1 under ambient conditions. The stored CO2 in the carbons can be readily recycled into Na2CO3 by impregnation with NaOH solution towards sustainable carbon sequestration. The present work affords a feasible strategy for massive reutilization of discarded duck down to manufacture advanced active carbons for applications including energy storage systems and CO2 capture.