Heteroatom Co-doping Research Articles

Synergistic enhancement of Ni2P anode for high lithium/sodium storage by N, P, S triply-doping and soft template-assisted strategy

Transition metal phosphides have demonstrated excellent performance in the field of energy conversion and storage, where nickel phosphide is one of the most prominent type of phosphides. However, achieving long cycle life with higher specific capacity in the case of Ni2P is still a great challenge. In this study, the composition and structure of Ni2P composites are rationally and precisely adjusted by heteroatoms doping and micelle-assisted methods to attain high capacity for longer cycles at high rate. Among all studied combinations, nickel phosphide particles anchored to triple heteroatom (N, P, S) doped carbon network skeleton (Ni2P@NPS) exhibited specific capacities of 727.3, 586.6, and 321.5 mA h g−1 after 1000 cycles at 1, 2 and 6 A g−1 for lithium-ion batteries (LIBs) and 230.1 mA h g−1 at 1 A g−1 for sodium-ion batteries (SIBs) after 560 cycles. The introduction of heteroatoms optimized the electronic structure of the electrode materials and promoted mass and charge transfer, while triple-heteroatom doped carbon substrates and uniformly dispersed spherical structures formed an active three-dimensional conductive network structure that provided a stronger driving force and richer channels for Li+/Na+ transport. Theoretical calculations showed that the high content of pyrrole nitrogen as well as the additional sulfur ensured improved electrical conductivity and enhanced ion adsorption performance. This study encourages further research into the synergistic effect of N, P, S co-doping materials for improving Li+/Na+ storage and the exploration of other heteroatom co-doping systems.

Thermoelectric properties of graphene through BN-ring doping: A theoretical investigation

Although graphene presents excellent transport properties, its potential for thermoelectric applications is still limited due to its low Seebeck coefficient and high thermal conductivity. Efforts to enhance its thermoelectric properties have involved the usage of carbon-based nanoribbons (Zheng et al., 2012; Hossain et al., 2016) [1,2], strain engineering (Nguyen et al., 2015), and heteroatom co-doping, particularly with nitrogen and/or boron atoms (Wang et al., 2018) [3]. In this work, multiscale simulation approaches combining density functional theory calculations and semi-empirical models are used to investigate the thermoelectric properties of graphene via borazine (B3N3)-ring doping. In particular, the bandgap engineering obtained by this doping technique (Caputo et al., 2022) can separate opposite electron and hole contributions and therefore results in a significant enhancement of the Seebeck effect and, accordingly, of the power factor. The results obtained are not only dependent on the concentration of B3N3 rings but are also notably influenced by their orientation configuration. Furthermore, the effects of distribution and rotational disorders are also considered, clarifying the thermoelectric properties of realistic systems. Lastly, the thermal lattice conductance is estimated revealing a substantial reduction of up to 40% compared to pristine graphene opening up the possibility of enhancing the thermoelectric efficiency of BNC materials. The present theoretical approach highlights how BN-ring doping can refine the thermoelectric properties of graphene, offering a pathway for enhancing its suitability in practical thermoelectric applications.

Direct pyrolysis fabrication of N/O/S self-doping hierarchical porous carbon from Platycladus Orientali leaves for supercapacitor

To meet the growing market requirement for low-cost supercapacitor electrode materials, N/O/S self-doping hierarchical porous carbon is successfully fabricated by direct pyrolysis of platycladus orientalLeaves (POL). The obtained carbon material exhibits wide application prospects, because of simple and green-environmental technology, low-cost and satisfactory electrochemical properties, which avoided complex preparation routes and consumption of expensive chemical reagents in the traditional activation process. Under the optimum pyrolysis temperature (850 °C), the obtained POL-derived carbon (POL-850) possesses a high specific surface area (1140.2 m2g−1), sheet-like hierarchical porous microstructure, and uniform ternary heteroatoms co-doping (O: 6.79 at.%; N: 3.45 at.% and S: 2.20 at.%). As an electrode material for supercapacitor, the specific capacitance of the POL-850 reaches 224.4 Fg−1 of 0.5 Ag−1and 156.0 Fg−1 at 30 Ag−1, revealing excellent rate performance. The capacitance retention maintains 96.3 % after 10,000 consecutive charge-discharge cycles at 20 Ag−1, demonstrating superior cycling stability. Additionally, the assembled carbon-based symmetric supercapacitor device delivers a satisfied energy density of 11.0 Wh kg−1 with the power density of 65 W kg−1 and ultralong cycle-lifetime with 95.65 % capacitance retention after 10,000 charge/discharge cycles, while the Coulombic efficiency is retaining up to approximately 100 %. This work provides an easy and cost-effective way to rapidly prepare N/O/S co-doping hierarchical porous carbon for supercapacitors, which is very suitable for large-scale production.

Boosted adsorption and oxidation performances in peroxymonosulfate (PMS)-based heterogeneous fenton-like reactions via P, N co-doping strategy

The heterogeneous Fenton-like reactions (HTFR) have attracted considerable interest for their efficacy in degrading pollutants. However, the development of effective strategies for enhancing performance in HTFR remains a subject of ongoing research. Herein, a synergistic adsorption and oxidation-dominated process was developed to overcome the bottlenecks of peroxymonosulfate (PMS)-based HTFR in terms of mass transfer and catalyst reactivity. Heteroatom (P, N) co-doping for manganese (Mn) was employed to fabricate an efficient catalyst, Mn@5-NPC-800, which exhibited exceptional abilities of adsorption and PMS activation. The enhanced performance of HTFR was attributed to the increased specific surface area (SSA) and enhanced yields of graphitic-N/MnIII of the catalyst, which facilitated reactant enrichment and electron transfer in the delocalized conjugated area, respectively. The PMS-based HTFR induced by Mn@5-NPC-800 for pollutant removal was characterized by a synergistic adsorption and reactive oxygen species (ROS)-dominated oxidation process. DFT calculations revealed that the N, P co-doped carbon matrix (NPC) acted as a conductive bridge, significantly improving electron transfer between MnP and PMS molecule, which was identified as a key factor in governing the catalytic performance. The investigation presents a suggestive example of employing a doping strategy to create a synergistic effect of adsorption and oxidation, thereby strengthening the performance of Fenton-like reactions.

Oxygen Vacancy-Controlled CuOx/N,Se Co-Doped Porous Carbon via Plasma-Treatment for Enhanced Electro-Reduction of Nitrate to Green Ammonia.

The electrochemical nitrate reduction reaction (NO3RR) is of significance in regards of environmentally friendly issues and green ammonia production. However, relatively low performance with a competitive hydrogen evolution reaction (HER) is a challenge to overcome for the NO3RR. In this study, oxygen vacancy-controlled copper oxide (CuOx) catalysts through a plasma treatment are successfully prepared and supported on high surface area porous carbon that are co-doped with N, Se species for its enhanced electrochemical properties. The oxygen vacancy-increased CuOx catalyst supported on the N,Se co-doped porous carbon (CuOx-H/NSePC) exhibited the highest NO3RR performance with faradaic efficiency (FE) of 87.2% and yield of 7.9mg cm-2h-1 for the ammonia production, representing significant enhancements of FE and ammonia yield as compared to the un-doped or the oxygen vacancy-decreased catalysts. This high performance should be attributed to a significant increase in the catalytic active sites with facilitated energetics from strategies of doping the catalytic materials and weakening the N─O bonding strength for the adsorption of NO3 - ions on the modulated oxygen vacancies. This results show a promise that co-doping of heteroatoms and regulating of oxygen vacancies can be key factors for performance enhancement, suggesting new guidelines for effective catalyst design of NO3RR.

Tailoring and understanding the lithium storage performance of triple-doped cobalt phosphide composites

Cobalt phosphide (CoP) with high theoretical capacity as well as ceramic-like and metal-like properties is considered as a promising anode for lithium-ion batteries (LIBs). However, the large volume change and sluggish kinetic response limit its practical application. The optimization of composition, structural control and performance regulation of CoP electrodes can be achieved by the bottom-up assembly technique of metal–organic frameworks (MOFs). Due to the effective electronic regulation and lithiophilicity brought by the multiple heteroatoms doping and the synergistic effect of the unique structure derived from MOFs, the N, O, P triple-doped carbon and CoP composites (ZCP@NOP) exhibited excellent rate capability (554.61 mAh g−1 at 2 A g−1) and cycling stability (806.7 mAh g−1 after 500 cycles at 0.5 A g−1). The essence and evolution of lithium storage mechanism in CoP electrodes are also confirmed by the ex-situ techniques. The synergistic benefits of heteroatom co-doping carbon and cobalt phosphide, such as the decrease of the diffusion energy barrier of Li-ions and the optimization of electronic structures, are highlighted in theoretical calculations. In conclusion, new thoughts and ideas for the creation of future battery anode are provided by the combination of the N, O, P co-doping and the adaptable structural adjustment technique.

Boron-manganese-nitrogen co-doped three-dimensional porous carbon realizes superior capacitive lithium-ion storage

Three-dimensional (3D) porous carbon has sufficient specific surface area and anchor positioning points. The pore structure facilitates uniform charge distribution, and buffers volume changes during stripping. However, single carbon materials have limited theoretical capacity and short cycle life. Here, 3D porous carbon material BCN/Mn-6 (B,N and Mn co-doped porous carbon with 6 mmol Mn content) co-doped with manganese, boron and nitrogen was synthesized by heat treatment. Affective modulation of the material structure and surface functional groups was achieved by adjusting the amount of manganese doping. The metal element doping can promote the diffusion of lithium ions, and the formed vacancies and defects can be used as lithium storage sites. Nitrogen doping can improve the dispersion and stability of metals and oxides, and regulate the redox capacity. Co-doping of metals and heteroatoms synergistically improves electrical conductivity. Thus, BCN/Mn-6 exhibits excellent cycling stability (99.60 % Coulombic efficiency after 300 cycles) and specific capacity (779.9 mAh/g), and shows capacity rise. This study provides a new direction for the preparation of carbon-based electrode materials doped with heteroatoms and the study of capacitive energy storage mechanisms.

Synergistic interaction of in situ S,N-codoping-mediated non-radical pathway for highly active and robust water decontamination

Metal-organic frameworks (MOFs)-derived heteroatom-doped carbon-based catalysts are commonly used in sewage treatment. However, the challenge lies in developing a simple route for heteroatom co-doping of MOFs-derived porous carbon that efficiently degrades organic pollutants without the need for additional post-treatment procedures. Herein, built-in Co nanoparticles are integrated with S,N-codoped porous carbon through a straightforward in situ co-doping strategy using ZnS nanoparticles as templates and a sulfur source. This approach simplifies the process of achieving S,N-codoping of zeolitic imidazolate frameworks-derived carbon without requiring extra nitrogen and sulfur sources or post-treatment procedures. The resulting Co@SNPC-900 catalyst demonstrates high catalytic performance in degrading tetracycline (TC) via peroxymonosulfate (PMS) activation, showing a removal efficiency of 97% in 30 min and excellent cycling stability. Furthermore, the Co@SNPC-900/PMS system shows strong resistance to changes in solution pH, interference from inorganic ions, and humic acid. The synergistic effects between S and N co-doping contribute to the formation of dominant non-radical pathways for boosting TC degradation. The study also elucidates three reaction pathways and identifies including sixteen intermediates with lower toxicity. This research presents a straightforward in situ co-doping strategy for producing highly active and durable built-in metal nanoparticles integrated porous carbon catalysts for environmental remediation.

Synergistic effects of fluorine and nitrogen dopants in fluorine/nitrogen-coordinated iron-co-doped carbon catalysts for enhanced oxygen reduction in alkaline media

The expensiveness of oxygen reduction reaction (ORR) catalyst materials especially Pt has hindered the commercialization of next-generation energy conversion devices including metal–air batteries and polymer electrolyte membrane fuel cells. Fe–N–C has drawn attention as a nonprecious metal catalyst owing to its high but commercially unsatisfactory ORR performance; nevertheless, additional heteroatom co-doping could help augment its ORR activity. Here we report nitrogen/fluorine-coordinated iron-co-doped carbon (Fe@NFC) catalysts with improved ORR performance in alkaline media. The annealing temperature affects the nitrogen/fluorine doping and functional group formation, as ascertained by an analysis of control samples annealed at various temperatures. To assess the synergy between the doped fluorine and nitrogen-coordinated iron, we compare the catalyst annealed at 700 °C (Fe@NFC700) with control samples containing different heteroatom dopants but annealed at 700 °C (Fe@NC, Fe@FC). Fe@NFC700 shows improved ORR kinetics and onset potential than those of Fe@NC and commercial Pt/C, respectively, in alkaline media.

Influence of nitrogen and sulfur co-doped activated carbon used as electrode material in EmiFSI ionic liquid toward high-energy supercapacitors

Porous carbon materials used as electrode materials could benefit from heteroatom co-doping to enhance their electrochemical properties. A one-step carbonization/co-doping procedure was developed to produce a nitrogen and sulfur (NS) co-doped activated carbon material from mangosteen shells (MS). Mangosteen is a tropical fruit globally well spread and cultivated in at least three continents and its shells represent an excellent porous carbon precursor. The amount of the doping agent (thiourea) was examined in relation to the morphological, structural, textural, and electrochemical performances of the material. The characterization results revealed that the 0.25 NS-doped MS AC electrode material was optimal and displayed a BET-specific surface area of 2308 m2 g−1. As measured by three-electrode configurations, this sample showed higher electrochemical performances than the non-doped MS AC with a specific capacity of 60.0 mAh g−1 at 0.5 A g−1. An increase in voltage (3.6 V) was observed in a symmetric supercapacitor using the doped material compared to the non-doped (2.8 V) in the same ionic liquid electrolyte. Further, the device demonstrated a specific capacity of 111.3 mAh g−1, a remarkable specific energy of 41.3 Wh kg−1 at 0.5 A g−1, and specific power of 7333.5 W kg−1 at 5 A g−1. These results pave the way for developing highly porous carbon materials with improved surface chemistry. The material can be used in different applications, including supercapacitors, batteries, and electrocatalysis at a reduced cost.

Multifunction-balanced porous carbon and its application in sulfur-loading host and separator modification for lithium–sulfur batteries

Lithium–sulfur batteries have been researched extensively because of their high energy density and low price. However, the poor conductivity of sulfur, the shuttle effect of polysulfide, the slow redox kinetics of sulfur species, and the significant volume expansion and contraction during charging and discharging have hindered the commercial application of lithium–sulfur batteries. In this study, a simple, scalable, and cost-effective strategy was developed to control the balance of the porosity, specific surface area, graphitization, heteroatom co-doping, and polar-polar interactions of a biomass carbon source. With this strategy, multifunctional porous carbon materials with three-dimensional network structures were prepared to serve as sulfur-loading hosts with high specific surface area, strong adsorption activity, and good conductivity. Moreover, the optimal porous carbon material was directly coated on a commercial separator, and the modified separator was found to further improve the electrochemical performance of a lithium–sulfur battery. As a result, for the battery with GPCS-3 as cathode electrode and modified separator as separator, the initial discharge capacity at 1.0C is 926.2 mAh g−1. After 300 cycles, the discharge capacity is 712.7 mAh g−1, and the average capacity decay is only 0.077 % per cycle. Since the three-dimensional network structure material exhibits good performance as a sulfur-loading host as well as the ability to effectively modify a separator, this study provides a valuable strategy for the fabrication of high energy density lithium–sulfur batteries.

Heteroatom co-doping (N, NS, NB) on carbon dots and their antibacterial and antioxidant properties

The development of new nanoparticle-based antibiotics with biocompatible properties is an emerging advance in nanotechnology. This study advocated the development of carbon dots (CDs) doped with nitrogen, nitrogen with sulfur, and nitrogen with boron (N, NS, and NB-CDs). This led to changes in the properties of the CDs, both chemically and biologically. A facile hydrothermal technique was used to synthesize CDs and the formation of CDs was confirmed through various analytical techniques. The CDs had sizes ranging from 3.2–4.8 nm and ζ-potential values of +13 to 27 mV. The doped CDs exhibited moderate changes in fluorescence behaviors depending on the excitation wavelength (λex). The N- and NB-doped CDs were effective at eliminating gram-negative pathogens (E. coli and K. pneumoniae), with minimum inhibitory concentrations (MIC) of 300 µg/mL and 400 µg/mL, respectively. The bactericidal effect of these CDs was attributed to the positive surface charge of the doped CDs and the production of ROS, which caused damage to the bacterial membrane and led to cell death. N- and NS-CDs also showed excellent free radical scavenging activities (<90 %) for DPPH and ABTS. The biocompatibility of doped CDs was examined by a human leukemia monocytic cell line (THP1 cell) and hemolysis test, which found that N, NB-CDs showed over 80 % viable cells at equivalent bactericidal (MBC) concentrations compared with NS-doped CDs. Our findings suggest that doping CDs with various dopants could be a new approach for selectively eliminating bacterial pathogens in hospital and biomedical environments.

Site dependent strategy for B/C/N homo and heteroatom co-doping in governing the optoelectronic behavior of MgO monolayers

Density functional theory calculations are carried out to investigate the effects of homo- and hetero-type co-doping of B, C and N on structural and electronic properties of MgO monolayers (MLs). The co-doping sites considered here are the possible equivalent and non-equivalent positions of a hexagon in a pristine MgO ML. The planarity of the monolayers is found to be governed by the site selectivity of the dopant atoms as well as the positions of doping. Planar monolayers have a higher likelihood of formation than the non-planar monolayers. In case of non-equivalent doping, the doping atoms always prefer positions that are closer. Stepwise substitution is more likely to occur than simultaneous substitution in formation of the co-doped monolayers. Most of the co-doping combinations introduce magnetism to the pristine MgO ML. Hetero-type monolayers prefer to be in magnetic states and even exhibit higher magnetic moments than homo-type MLs, with a maximum value of 4 μB for B–N co-doping. Almost all the monolayers are semiconducting with significantly reduced band gaps, while few hetero-type monolayers are metallic in nature. The electronic energy band gaps of the monolayers are compatible with the IR and visible regions of the electromagnetic spectrum. The overall tuning of the electronic properties renders the co-doped MgO monolayers effective for applications in spintronics and optoelectronics.

Controllable hydrogen release from NH3BH3 hydrolysis over Ru ultrafine particles stabilized on agriculture waste-derived carbon

Simultaneously considering cost, safety and catalytic efficiency, the development of a cost-effective and high-performance catalyst is significant and challenging for controllable hydrogen release from ammonia borane (AB, NH3BH3) hydrolysis. In this work, Ru ultrafine particles are evenly and firmly stabilized on wheat straw-derived porous carbon through a facile procedure. Specifically, attributed to the abundant co-doping of heteroatoms (namely, N and O) and suitable hierarchical porous structure of WSC-1.0 with large specific surface area (1000 m2 g−1), which is prepared with a mass ratio of 1: 1 for K2CO3 to the pre-carbonized biomass waste, as well as high dispersion (32.6%) of Ru ultrafine particles with an average size of 1.4 ± 0.3 nm, the optimal Ru/WSC-1.0 displays exceptional catalytic performance in the hydrolysis of AB. The corresponding turnover frequency (TOF) and specific reaction rate (rB) are 167.7 min−1 and 4.07 × 104 mL min−1 gRu−1, respectively, and the apparent activation energy is 40.94 kJ mol−1. Upon adding NaOH (1.0 M), the hydrolysis rate can be remarkably accelerated (TOF = 401.4 min−1, rB = 9.75 × 104 mL min−1 gRu−1). The isotope experiments show that the scission of an O-H bond in H2O by oxidative addition is the decisive step in this reaction. Impressively, the effective “on-off” control for the hydrolytic dehydrogenation reaction over Ru/WSC-1.0 can be easily realized by introducing certain amounts of Zn(NO3)2 and EDTA-2Na, separately. Our work delivers a facile approach for efficient utilization of agricultural wastes and offers a robust and cost-effective catalyst for the controllable hydrogen evolution from AB hydrolysis.

Enhancement of Mn-N-C single atom catalysts via sulfur and/or oxygen co-doping for oxygen reduction in acidic conditions: Unveiling the catalyst durability in fuel cells

Carbon-supported single Mn sites coordinated with nitrogen (Mn-N-C) catalysts are amongst the most favorable platinum group metal-free (PGM-free) catalysts for proton exchange membrane fuel cells (PEMFCs). However, the high overpotential of these catalysts, limits their application for oxygen reduction reaction (ORR). Experiments showed that O and S heteroatom co-doping increases the catalytic activity of Mn-N-C catalysts for electrochemical gas conversion. This prompted us to perform a systematic investigation of the formed co-doped configurations at the atomic scale and to study the corresponding reaction mechanisms for oxygen reduction in acidic environment. All probable configurations for Mn-NxOySz/C10 complexes are considered and the most stable and durable structures are selected as ORR active catalysts. Our results confirm the strong stabilization of the Mn sites over N4- and N3-doped carbonaceous support and consequently their stability against oxidation in contrast to other O and/or S co-doped heterostructures.

Iron-loading N and S heteroatom doped porous carbon derived from chitosan and CdS-Tetrahymena thermophila for peroxymonosulfate activation

Transforming waste into resources is an important strategy to enhance the economic efficiency and reduce the waste entering the environment. In this work, iron-loading N and S co-doped porous carbon materials, as peroxymonosulfate (PMS) activator for pollutants degradation, were prepared by pyrolysis of the mixture of iron loading chitosan and CdS-Tetrahymena thermophila under N2 flow. Chitosan is mainly derived from the shell waste of shrimp and crab, and CdS-Tetrahymena thermophila is produced in the removing process of Cd2+ pollution bioremediation using Tetrahymena thermophila. The synergistic effects of iron related species and heteroatoms (S/N) co-doped porous carbon in the obtained carbon materials improved the performance for activating PMS. The prepared Fe-S-CS-1-900 exhibited high performance for the degradation of Rhodamine B (RhB) by activating PMS. Radical quenching tests and electron paramagnetic resonance measurements suggested that superoxide radical (O2−) and singlet oxygen (1O2) were the primary reactive oxygen species in RhB degradation. These results propose new insights of using biomass waste to derive Fe-loading N and S heteroatom co-doping carbon as PMS activator applied in the removal of organic pollutants.

Heteroatom tuning in agarose derived carbon aerogel for enhanced potassium ion multiple energy storage

AbstractThe incorporation of heteroatoms into carbon aerogels (CAs) can lead to structural distortions and changes in active sites due to their smaller size and electronegativity compared to pure carbon. However, the evolution of the electronic structure from single‐atom doping to heteroatom codoping in CAs has not yet been thoroughly investigated, and the impact of codoping on potassium ion (K+) storage and diffusion pathways as electrode material remains unclear. In this study, experimental and theoretical simulations were conducted to demonstrate that heteroatom codoping, composed of multiple heteroatoms (O/N/B) with different properties, has the potential to improve the electrical properties and stability of CAs compared to single‐atom doping. Electronic states near the Fermi level have revealed that doping with O/N/B generates a greater number of active centers on adjacent carbon atoms than doping with O and O/N atoms. As a result of synergy with enhanced wetting ability (contact angle of 9.26°) derived from amino groups and hierarchical porous structure, ON‐CA has the most optimized adsorption capacity (−1.62 eV) and diffusion barrier (0.12 eV) of K+. The optimal pathway of K+ in ON‐CA is along the carbon ring with N or O doping. As K+ storage material for supercapacitors and ion batteries, it shows an outstanding specific capacity and capacitance, electrochemical stability, and rate performance. Especially, the assembled symmetrical K+ supercapacitor demonstrates an energy density of 51.8 Wh kg−1, an ultrahigh power density of 443 W kg−1, and outstanding cycling stability (maintaining 83.3% after 10,000 cycles in 1 M KPF6 organic electrolyte). This research provides valuable insights into the design of high‐performance potassium ion storage materials.

N, S co-doped porous carbon nanosheet foam as MALDI matrix for efficient and direct profiling of biomolecules and environmental contaminants

It is still urgent to develop a powerful method for high-throughput and sensitive analysis of various small biomolecules and environmental contaminants. Herein, a three-dimensional foam consisting of nitrogen and sulfur co-doped porous carbon (N, S-C) nanosheet synthesized was served as an excellent matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) efficiently and directly detecting various small biomolecules and pollutant compounds. This N, S-C nanosheet possessed the advantages of carbon foam for resonant chamber, high-contents of N/S heteroatoms co-doping, large surface area, hierarchical pore and good UV absorption. The use of N, S-C matrix could exhibit higher MS intensities, lower background noise, better salt tolerance and higher sensitivity for probing the various analytes, much superior to the traditional CHCA (α-cyano-4-hydroxycinnamic acid) matrix and control materials (C and N-C). The limit of detection (LOD)s of 1-hydroxy-pyrene, 4-nitrocatechol and nitroguaiacol were calculated to be 0.1 μg/mL, 1 μg/mL and 8 μg/mL at a signal-to-noise ratio (S/N) of 3. Moreover, the rapid and precise detections of 4-nitrocatechol, nitroguaiacol, and 1-hydroxy-pyrene in PM2.5 real sample have also been achieved. Through density functional theory (DFT) simulations, we reveal the sensing mechanism of small molecular deprotonation with the N and S co-doping into carbon matrix. This work may be promising to provide an excellent carbon matrix for the analysis of MALDI-TOF MS method in the biological and environmental field.

Role of Noncovalent Interactions in N,P-Functionalized Luminescent Carbon Dots for Ultrasensitive Detection of Moisture in D2O: Boosting Visible-NIR Light Sensitivity.

It is highly desirable to design cost-efficient and eco-friendly fluorometric sensors that can efficiently detect water contamination in D2O and other expensive organic solvents. Herein, we have synthesized N,P-codoped carbon dots (N,P-CDs) from o-phenylene diamine (o-PDA) and H3PO4 through the bottom-up carbonization method. Heteroatom co-doping increases the absorption cross section in the visible-NIR range, followed by the formation of stable emissive states in longer-wavelength regions. We have critically investigated the noncovalent interactions (especially H-bonding interactions) of various surface functional groups with surrounding solvent media through a detailed structure-property correlation. Based on the sensitivity of noncovalent H-bonding interactions to the stability of longer-wavelength emissive domains, we have utilized these N,P-CDs as cost-effective fluorometric sensors of water/moisture contamination in D2O especially under visible-NIR light; the optical sensitivity reaches up to 0.1 volume (%) level. The detailed sensing mechanism has been further supported by a computational study through a simple visualization approach by mapping and analyzing all possible noncovalent interactions between the CDs and the solvent medium.

Insights into Enhanced Cycling and Rate Stability of LiNi0.88Co0.09Al0.03O2 via Co-doping for Lithium-Ion Batteries

Ni-rich-layered structure cathode materials are receiving great attention in the next-generation lithium-ion batteries due to their high specific capacity and energy density. However, the poor cycle and rate capability of the materials, caused by the instability of structures, are limiting their applications. In this work, we provide a co-doping method to address the above issue for Ni-rich LiNi0.88Co0.09Al0.03O2 cathodes, which greatly improves the structural stability due to the suppression of the phase transformation from the layered to NiO-like (rocksalt) phase. Consequently, the parasitic reaction of the interface is abated. Based on our method, the co-doped Li(Ni0.88Co0.09Al0.03)0.98Cr0.01Mo0.01O2 shows the excellent capacity retention, ∼89.2% (174.3 mA h/g) with a current density of 100 mA/g after 200 cycles, much higher than that of the pure LiNi0.88Co0.09Al0.03O2, only remaining 75.2 mA h/g (about 35.4% capacity retention). In addition, the rate retention of Li(Ni0.88Co0.09Al0.03)0.98Cr0.01Mo0.01O2 also demonstrates the superior stability (92.1, 90.2, 86.2, and 77.6% at 100, 200, 400, and 1000 mA/g) with improving the electrochemical kinetics of materials. This work provides a feasible path to improve the electrochemical behaviors of Ni-rich-layered structure cathodes via heteroatom co-doping.