Energy Barrier For Decomposition Research Articles

Thermal decomposition behaviors of adamantane and 1-methyladamantane in oxygen atmosphere: ReaxFF molecular dynamics simulation

High energy density fuels (HEDFs) have garnered considerable interest in the aerospace applications due to their high density and effective heat dissipation capabilities. However, there is still no clear understanding of the pyrolysis and oxidation mechanisms of HEDFs. In this work, a computational strategy based on ReaxFF molecular dynamics reveals dehydrogenation and ring-opening reaction events for adamantane and 1-methyladamantane. A comparative analysis of the initial decomposition behavior, intermediate reaction mechanism, and final product distribution demonstrates that the decay of the reactants is dependent on temperature and oxygen concentration. The main decomposition pathways of adamantane and 1-methyladamantane involve multi-step dehydrogenation and ring opening by the following reaction: i. C10H16 → C10H15 → C7H10 + C3H5, ii. C10H16 → C10H12, iii. C11H18 → C11H16, iv. C11H18 → C11H15 → C2H4 + C9H11. C7H10, C3H5, and C9H11 undergo further bond-breaking reactions to form linear hydrocarbon chains. At low temperatures, C10H16 and C11H18 exhibit a preference for reacting with OH and HO2, accounting for 15 %–35 % of the reactions. At high temperatures, the preferred reaction for C10H16 and C11H18 is with O2, accounting for 33 %–64 % of the reactions. The bridge carbon atom acts as the initial dehydrogenation site for both adamantane and 1-methyladamantane, as well as the active site for ring opening. The decomposition energy barrier for 1-methyladamantane (108.16–130.39 kJ/mol) is lower than that for adamantane (130.72–142.61 kJ/mol). Our findings shed light on the complicated interplay of oxidation of adamantane and 1-methyladamantane.

Multispecies-coadsorption-induced rapid preparation of graphene glass fiber fabric and applications in flexible pressure sensor

Direct chemical vapor deposition (CVD) growth of graphene on dielectric/insulating materials is a promising strategy for subsequent transfer-free applications of graphene. However, graphene growth on noncatalytic substrates is faced with thorny issues, especially the limited growth rate, which severely hinders mass production and practical applications. Herein, graphene glass fiber fabric (GGFF) is developed by graphene CVD growth on glass fiber fabric. Dichloromethane is applied as a carbon precursor to accelerate graphene growth, which has a low decomposition energy barrier, and more importantly, the produced high-electronegativity Cl radical can enhance adsorption of active carbon species by Cl–CH2 coadsorption and facilitate H detachment from graphene edges. Consequently, the growth rate is increased by ~3 orders of magnitude and carbon utilization by ~960-fold, compared with conventional methane precursor. The advantageous hierarchical conductive configuration of lightweight, flexible GGFF makes it an ultrasensitive pressure sensor for human motion and physiological monitoring, such as pulse and vocal signals.

First-Principles Investigation of Phosphorus-Doped Graphitic Carbon Nitride as Anchoring Material for the Lithium-Sulfur Battery.

The utilization of lithium-sulfur battery is hindered by various challenges, including the "shuttle effect", limited sulfur utilization, and the sluggish conversion kinetics of lithium polysulfides (LiPSs). In the present work, a theoretical design for the viability of graphitic carbon nitride (g-C3N4) and phosphorus-doping graphitic carbon nitride substrates (P-g-C3N4) as promising host materials in a Li-S battery was conducted utilizing first-principles calculations. The PDOS shows that when the P atom is introduced, the 2p of the N atom is affected by the 2p orbital of the P atom, which increases the energy band of phosphorus-doping substrates. The energy bands of PC and Pi are 0.12 eV and 0.20 eV, respectively. When the lithium polysulfides are adsorbed on four substrates, the overall adsorption energy of PC is 48-77% higher than that of graphitic carbon nitride, in which the charge transfer of long-chain lithium polysulfides increase by more than 1.5-fold. It is found that there are powerful Li-N bonds between lithium polysulfides and P-g-C3N4 substrates. Compared with the graphitic carbon nitride monolayer, the anchoring effect of the LiPSs@P-g-C3N4 substrate is enhanced, which is beneficial for inhibiting the shuttle of high-order lithium polysulfides. Furthermore, the catalytic performance of the P-g-C3N4 substrate is assessed in terms of the S8 reduction pathway and the decomposition of Li2S; the decomposition energy barrier of the P-g-C3N4 substrate decrease by 10% to 18%. The calculated results show that P-g-C3N4 can promote the reduction of S8 molecules and Li-S bond cleavage within Li2S, thus improving the utilization of sulfur-active substances and the ability of rapid reaction kinetics. Therefore, the P-g-C3N4 substrates are a promising high-performance lithium-sulfur battery anchoring material.

The Role of Transition Metal Versus Coordination Mode in Single-Atom Catalyst for Electrocatalytic Sulfur Reduction Reaction.

Electrocatalytic sulfur reduction reaction (SRR) is emerging as an effective strategy to combat the polysulfide shuttling effect, which remains a critical factor impeding the practical application of the Li-S battery. Single-atom catalyst (SAC), one of the most studied catalytic materials, has shown considerable potential in addressing the polysulfide shuttling effect in a Li-S battery. However, the role played by transition metal vs coordination mode in electrocatalytic SRR is trial-and-error, and the general understanding that guides the synthesis of the specific SAC with desired property remains elusive. Herein, we use first-principles calculations and machine learning to screen a comprehensive data set of graphene-based SACs with different transition metals, heteroatom doping, and coordination modes. The results reveal that the type of transition metal plays the decisive role in SAC for electrocatalytic SRR, rather than the coordination mode. Specifically, the 3d transition metals exhibit admirable electrocatalytic SRR activity for all of the coordination modes. Compared with the reported N3C1 and N4 coordinated graphene-based SACs covering 3d, 4d, and 5d transition metals, the proposed para-MnO2C2 and para-FeN2C2 possess significant advantages on the electrocatalytic SRR, including a considerably low overpotential down to 1 mV and reduced Li2S decomposition energy barrier, both suggesting an accelerated conversion process among the polysulfides. This study may clarify some understanding of the role played by transition metal vs coordination mode for SAC materials with specific structure and desired catalytic properties toward electrocatalytic SRR and beyond.

Three Birds with One Stone: Multifunctional Separators Based on SnSe Nanosheets Enable High‐Performance Li‐, Na‐ and K‐Sulfur Batteries

AbstractAlkali metal‐sulfur batteries (MSBs) are one of the most promising next‐generation energy storage technologies due to their high energy density and potential for low cost. They are nonetheless constrained by the sluggish conversion of metal polysulfides (MPS) during the charge/discharge process. Herein, a multifunctional separator able to trap the MPS and catalyze their conversion in the three main MSB chemistries, Li‐, Na‐, and K‐MSBs, is demonstrated. More in detail, SnSe nanosheets are introduced as additive into the cathode side of the glass microfiber (GF) separator of the MSB. Taking lithium‐sulfur batteries (LSBs) as an example, it is demonstrated that the GF‐SnSe separator (GF@SnSe) shows strong chemical affinity to lithium polysulfides (LiPS) and superior catalytic activity, inhibiting the transport of LiPSs to the anode and accelerating their conversion. Combining experimental and calculation results, the SnSe additive is shown to decrease the Li2S decomposition energy barrier. Overall, GF@SnSe separators provide significantly improved LSB rate performance and cycling stability with a 0.049% capacity decay per cycle. Besides, the GF@SnSe separator promotes the electrochemical performance of sodium‐sulfur and potassium‐sulfur batteries. Overall, this work presents a significant advancement in the development of multifunctional separators in LSBs as well as the emerging Na‐S and K‐S systems.

Eco-innovation in energy: Solid degradation kinetics of rejected red macroalgae (Kappaphycopsis cottonii) for bio-oil and biochar production

In the pursuit of renewable energy sources, biomass conversion into biofuels has garnered attention as a sustainable alternative to fossil fuels. This research focuses on the pyrolytic conversion of red macroalgae, specifically rejected Kappaphycus cottonii, an underutilized biomass in Indonesia, into valuable bio-energy carriers, while analyzing the solid degradation kinetics involved. The dried K. cottonii underwent slow pyrolysis at varying temperatures (400–600 °C) and time intervals (10–50 min). The impact of these variables on the yield of bio-oil and biochar, alongside the thermogravimetric profiles indicating mass loss, was thoroughly assessed. The study also explores the chemical kinetics of the decomposition process, utilizing the first-order reaction model to analyze the solid biomass conversion rate, activation energy, and frequency factor. Key findings demonstrate that the optimal pyrolysis temperature for maximizing bio-oil yield was precisely 500 °C, beyond which thermal cracking led to yield reductions. Reaction times also greatly affect yield, highlighting the importance of optimized pyrolysis conditions. The determined activation energy and frequency factor, based on the Arrhenius equation, highlighted K. cottonii's lower decomposition energy barrier relative to terrestrial biomass. This distinction is largely ascribed to its unique chemical makeup, notably a lower lignin content, positioning K. cottonii as an advantageous feedstock for biofuel production through pyrolysis.

Theoretical study on the utilization of N, O-functionalized graphene quantum dots in Li-S batteries

Lithium-sulfur (Li-S) batteries have high theoretical capacity and high energy density, and their practical application is difficult because of the “shuttle effect” induced by lithium polysulfides (LiPSs) and the difficulty of insoluble Li2S decomposition. Functionalized graphene quantum dots (GQDs) can anchor LiPSs and suppress the “shuttle effect” because of the various polar functional groups. This work investigates the effect of the size of GQDs and the N/O functional groups on the anchoring performance by first-principles calculations. In addition, the influence on the decomposition of Li2S, the diffusion of Li+, and the Gibbs free energy needed for the sulfur reduction reaction was also studied. The results show that the GQDs can effectively anchor LiPSs when the size is larger than 1.44 nm, and all the N/O-functionalized GQDs can also effectively anchor LiPSs. Among these N/O-functionalized GQDs, GQDs-COOH has the smallest Li+ diffusion energy barrier (0.52 eV) and low Li2S decomposition energy barrier (1.12 eV). It indicates that GQDs-COOH enables the rapid diffusion of Li+, ensures the smooth decomposition of Li2S, and catalyzes the effective conversion of LiPSs. Moreover, this work will promote the application of GQDs in Li-S batteries.

Accelerating polysulfides conversion by constructing Lewis acidic Mn-N4 single atomic sites for Li-S battery with high sulfur loading

The shuttle effects of lithium polysulfides (LiPSs) and the sluggish conversion reaction between LiPSs and Li2S significantly limit the electrochemical performance of Li-S batteries. In this study, a unique structured single atomic Mn anchored on nitrogen-doped carbon black (SAMnN@C) is developed to address above challenges. Physical characterizations confirmed atomically dispersed Mn atoms were anchored on carbon by 4 N atoms forming a typical structure of planar Mn-N4. Li-S battery assembled by as-prepared SAMnN@C displayed a discharge capacity of 1400 mA h g-1 at 0.1C, and outstanding stability with a capacity decay rate of 0.052 % per cycle during 1000 cycles at 1C. Moreover, excellent electrochemical performances could be preserved even if the S mass loading increased to 5.7 mg cm−2 with ∼ 5 μL (mg S)-1 electrolyte. The mechanism studies revealed that SAMnN@C exhibited a unique Lewis acid-base interaction between Mn-N4 site and S atom, which significantly lowered the decomposition energy barrier of Li2S2, and eventually accelerated the sluggish solid-state conversion reaction of Li2S2 to Li2S. This study is believed to shed light on the mechanism of SACs for high performance Li-S batteries.

Theoretical study of highly efficient VS2-based single-atom catalysts for lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries have become a research hotspot due to their high energy density. However, they also have certain disadvantages and limitations. To enhance the performance of Li-S batteries, this study focuses on the utilization of transition metal (TM)-embedded vanadium disulfide (VS2) materials as cathode catalysts. Using density functional theory (DFT), comprehensive calculations and atomic-level screening of ten TM atoms were conducted to understand the underlying mechanisms and explore the potential of TM@VS2 catalysts for enhancing battery performance. The computational results indicate that five selected catalysts possess sufficient bonding strength towards high-order lithium polysulfide intermediates by the formation of a significant covalent bond between S atoms in Li2Sn and TM atoms, thereby effectively suppressing the shuttle effect. The Ni@VS2 catalyst can effectively decrease the decomposition energy barrier of Li2S in the charge reaction and can have an optimal Gibbs free energy at the rate-determining step among TM@VS2 catalysts for the discharge reaction. This study elucidates the mechanism of VS2-based transition-metal single-atom catalysts and provides an effective reference for the anchoring of TM atoms on other materials.

Novel cage-like all-nitrogen molecular crystal stable under ambient conditions

Exploring whether cage-like molecular crystals similar to those in carbon systems exist in all-nitrogen systems is not only of great theoretical significance, but also of great practical application value as high-energy-density materials. Here, we predict a new type of cage-like all-nitrogen Td-N4 molecular crystal by using the CALYPSO method. The structure has mechanical and dynamic stability under ambient pressure. Moreover, Td-N4 molecular crystal has excellent thermal stability and can be stabilized to a high temperature of 2400 K. The reason why Td-N4 molecular crystal has such excellent stability is due to the high decomposition energy barrier (251.5 kJ/mol), and the most essential reason may be due to the strong double spherically aromatic of the molecule with the nucleus-independent chemical shift (NICS) of −70.5 ppm. It is worth noting that the energy density of the Td-N4 molecular crystal is 11.89 kJ/g, which is three times that of the TNT (4.3 kJ/g), twice that of HMX (5.7 kJ/g), and higher than that of the well-known cg-N structure (9.7 kJ/g). In addition, Td-N4 molecular crystal also has excellent properties with high Heat of detonation, detonation pressure and detonation velocity. The prediction of Td-N4 molecular crystal provides a very promising candidate for high energy density materials.

Oxygen self-doping pyrolyzed polyacrylic acid as sulfur host with physical/chemical adsorption dual function for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with high theoretical capacity and energy density need to solve problems such as the high decomposition energy barrier of Li2S and large volume change of sulfur in the charging process caused by the shuttle effect before practical application. Herein, a green synthesis method is used to prepare polyacrylic acid (PAA) superabsorbent material, and then the pyrolyzed PAA (P/PAA) material is obtained as the positive electrode of Li-S battery. Density functional calculation reveals that the oxygen self-doping pyrolyzed polyacrylic acid (P/PAA) delivered stronger binding energy toward Li2S species in carbonyl C=O than that of graphite powder (GP) which are −1.58 eV and −1.02 eV, respectively. Coupled with the distribution of relaxation time analysis and the in-situ electrochemical impedance approach, it is further demonstrated that the designed P/PAA as sulfur host plays a physical/chemical adsorption dual function in maintaining the stability and rate performance of batteries. With an initial discharge capacity of 1258 mAh/g at 0.1 C and a minimal capacity decline of 0.05% per cycle even after 800 cycles at 0.5 C, the produced cathode demonstrated outstanding electrochemical performance. The average Coulombic efficiency is nearly 100%. The P/PAA electrodes may typically retain 96% of their capacity while declining on average only 0.033% per cycle after 130 cycles at 3 C. This effort provides a new method for the future development of heteroatomic self-doping superabsorbent with promising adsorption properties for polysulfides as cathode materials of Li-S batteries.

Oxygen Defect‐Rich WO3−x–W3N4 Mott–Schottky Heterojunctions Enabling Bidirectional Catalysis for Sulfur Cathode

AbstractThe serious shuttle effect and intrinsically sluggish oxidation–reduction reaction kinetics of polysulfides severely hinder the practical commercialization of lithium–sulfur (Li–S) batteries. Herein, oxygen‐defect‐rich WO3−x–W3N4 Mott–Schottky heterojunctions are designed as efficient catalysts. Based on theoretical calculations and comprehensive experimental characterization, WO3−x–W3N4 exhibits a lower free energy change (1.03 eV) and Li2S decomposition energy barrier (0.92 eV) than WO3 and W3N4, which significantly enhances the sulfur reduction reaction (SRR) activity. Furthermore, a relationship between the catalytic activity and the energy gaps in the d and p bands centers (Δd–p) is also established, with the low Δd–p of the heterojunction leading to a lower antibonding state energy, which promotes electron transfer and interfacial redox kinetics. Oxygen vacancies can improve the catalytic effect without affecting adsorption. Hence, the Li–S battery using WO3−x–W3N4@CC/S exhibited outstanding rate and duration performance (913.9 mAh g–1 at 2 C, stable 400 cycles at 1 C). Impressively, the battery achieves a high areal capacity of 5.0 mAh cm−2 under a high sulfur loading of 4.98 mg cm−2.

Vanadium as Auxiliary for Fe-V Dual-Atom Electrocatalyst in Lithium-Sulfur Batteries: "3D in 2D" Morphology Inducer and Coordination Structure Regulator.

The undesirable shuttling behavior, the sluggish redox kinetics of liquid-solid transformation, and the large energy barrier for decomposition of Li2S have been the recognized problems impeding the practical application of lithium-sulfur batteries. Herein, inspired by the spectacular catalytic activity of the Fe/V center in bioenzyme for nitrogen/sulfur fixation, we design an integrated electrocatalyst comprising N-bridged Fe-V dual-atom active sites (Fe/V-N7) dispersed on ingenious "3D in 2D" carbon nanosheets (denoted as DAC), in which vanadium induces the laminar structure and regulates the coordination configuration of active centers simultaneously, realizing the redistribution of the 3d-orbital electrons of Fe centers. The high coupling/conjunction between Fe/V 3d electrons and S 2p electrons shows strong affinity and enhanced reactivity of DAC-Li2Sn (1 ≤ n ≤ 8) systems. Thus, DAC presents strengthened chemisorption ability toward polysulfides and significantly boosts bidirectional sulfur redox reaction kinetics, which have been evidenced theoretically and experimentally. Besides, the well-designed "3D in 2D" morphology of DAC enables uniform sulfur distribution, facilitated electron transfer, and abundant active sites exposure. Therefore, the assembled Li-S cells present outstanding cycling stability (637.3 mAh g-1 after 1000 cycles at 1 C) and high rate capability (711 mAh g-1 at 4 C) under high sulfur content (70 wt %).

Waste biomass-derived N, P co-doping carbon aerogel-coated CoxFe1−xP with modulated electron density for efficient electrooxidation of contaminants

Developing low-cost, green, high-performing electrode materials to address environmental pollutants and the energy crisis is significant but challenging. Herein, the bimetallic iron cobalt phosphide coated in waste biomass-derived N, P co-doping carbon (CoxFe1−xP@NPC) is constructed. Furthermore, the active site density and the water decomposition energy barrier of surface-coated NPC are modulated by optimizing the electronic structure of CoxFe1−xP via doping engineering. The Fe-modulated CoxFe1−xP@NPC exhibits a hierarchical porous self-supporting structure and excellent physical & chemical properties with excellent electrooxidation performance, achieving over 95% removal of TCH within 60 min. The density functional theory (DFT) calculations further confirms that N carries more positive charge and P carries more negative charge in the NPC of CoxFe1−xP@NPC with Fe modulation, which can promote the adsorption and dissociation of water molecules. Of note, Co0.75Fe025P@NPC displays a low water dissociation energy barrier to produce ·OH and a high energy barrier to produce O2 than its counterparts. This study offers new insight into controllable modulation of biomass carbon-based composite electrode catalytic activity for high-efficiency degradation of contaminants.

Polynitrogen clusters interaction with water: experimental and theoretical perspectives

Polynitrogen clusters are of great interest as potential high-energy-density materials (HEDMs). However, it is still a challenge to effectively manufacture pure nitrogen clusters. Here, we present a method to produce all-nitrogen clusters ranging in size from 3 to 10 using a self-developed apparatus consisting of a laser vaporization cluster source and a mass spectrometer. The results indicate that the mass peak of the N4 + cluster is dominant, and the cooling of the cluster source with liquid nitrogen effectively enhanced the intensities of larger nitrogen clusters. The trace amounts of water in the carrier gas affects the relative signal intensities of nitrogen clusters, suggesting that water molecules can affect their stabilities. The geometrical structures of the N(n = 3–10) clusters are determined by CALYPSO cluster structural search method and density functional theory calculations. A series of promising polynitrogen clusters, such as Z-shaped N clusters and bicyclic N clusters, are identified. The molecular dynamics simulations indicate the decomposition energy barrier of (N4–H2O)+ cluster is lower than that of N4 + cluster by 2.3 kcal mol−1, while the decomposition energy barrier of (N8–H2O)+ cluster is higher than that of N8 + cluster by 1.4 kcal mol−1. These findings provide useful information for the generation and stabilization of polynitrogen clusters, which are valuable for the design and synthesis of HEDMs.

Concentration induced modulation of solvation structure for efficient lithium metal battery by regulating energy level of LUMO orbital

Nitrile electrolytes have attracted extensive attention for achieving high-voltage lithium metal batteries. However, the poor compatibility of nitrile electrolyte with Li anode remains a huge challenge owing to severe side reactions. Herein, changing concentration of LiTFSI in succinonitrile (SN) is proposed to improve interface compatibility by regulating the solvation structure. The higher coordination number (1.3) of TFSI− in high concentration electrolytes results in a LiF-rich SEI film, accounting for the superior performance of LiNi0.8Co0.1Mn0.1O2|Li cell with negligible capacity fade after 100 cycles at 0.5 C. Density functional theory (DFT) suggests that the solvation structure with a high coordination number of TFSI− towards Li+ leads to a reduced Lowest Unoccupied Molecular Orbital (LUMO) energy level, which promotes the decomposition of TFSI− to form LiF-rich film. Also, a reduced decomposition energy barrier of anion is demonstrated. This work provides an encouraging way to enhance interface stability via modulating the solvation structure achieved by regulating concentration.

Desulfurization mechanism of thiophene compounds in supercritical water

Thiophene and its derivatives, the major sulfur-containing compounds widely exist in crude oil, which will cause air pollution by releasing SOx during direct combustion. Hence, the desulfurization of thiophene compounds was essential. Supercritical water (SCW) treatment is a potential technique for sulfur removal and energy conversion. In this work, density functional theory (DFT) calculations and experiments are employed to study the decomposition of thiophene compounds in SCW. DFT shows that H2O plays the role of reactant as well as catalyst in the delocalization destruction of thiophene. Additionally, H2, the main gaseous product in SCW process, also promotes the decomposition of thiophene. What’s more, a larger substituent in thiophene lead to a higher reaction energy barrier for decomposition. Experimental results show that the maximum desulfurization rate of thiophene reaches 91.54% in SCW, which is almost 1.5 times as that in pyrolysis (61.06%) at 700 °C and 30 min. And dibenzothiophene with the largest substituent make the poorest performance in desulfurization compared with methyl-thiophene and benzothiophene, which proved the results of DFT calculations. Based on the above research, the detailed reaction pathways of dibenzothiophene are proposed, which may be critical in understanding the desulfurization of thiophene compounds and the resource utilization of crude oil in SCW.

CoFe2O4@rGO as a Separator Coating for Advanced Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are hindered by the undesired shuttle effect and sluggish electrochemical conversion kinetics. Herein, a well‐designed CoFe2O4@reduced graphene oxide (CFO@rGO) composite is used to modify the separator to develop a multifunctional polysulfide barrier. Density functional theory (DFT) calculations confirm that highly electronegative oxygen ions in CFO tend to bond with transition metal (TM) ions at octahedral (Oh) sites, which induces the formation of FeS and CoS bonds between CFO and polysulfides. This indicates that CFO can effectively anchor polysulfides. Furthermore, the low Li2S decomposition energy barrier and Li+ diffusion energy barrier reveal that CFO can accelerate the redox reaction kinetics of sulfur species. Electronic structure calculations speculate that the low‐energy barrier can be attributed to the electron‐hopping phenomenon between TM ions of different valence states at Oh sites. Benefiting from these advantages, a CFO@rGO/PP separator demonstrates satisfactory cycling performance (0.087% capacity decay rate at 2C with 500 cycles) and superb rate performance (686 mAh g−1 at 5C). This work provides a valuable reference for future research on spinel‐type materials as electrocatalysts for Li–S batteries.

Ultrafast Strategy to Fabricate Sulfur Cathodes for High-Performance Lithium-Sulfur Batteries.

Based on the different dielectric properties of materials and the selective heating property of microwaves, the ultrafast (30 s) preparation of S-NiS2@SP@Bitu as a cathode material for lithium-sulfur batteries was achieved using bitumen, sulfur, Super P, and nickel naphthenate as raw materials for the first time, under microwave treatment. NiS2@SP@Bitu forms Li-N, Li-O, Li-S, and Ni-S bonds with polysulfide, which contributes to promoting the adsorption of polysulfide, reducing the precipitation and decomposition energy barrier of Li2S, and accelerating the catalytic conversion of polysulfide, as result of inhibiting the "shuttle effect" and improving the electrochemical performance. S-NiS2@SP@Bitu as the sulfur cathode material demonstrates outstanding rate performance (518.6 mAh g-1 at 4C), and stable cycling performance. The lithium-sulfur battery with a sulfur loading of 4.8 mg cm-2 shows an areal capacity of 4.6 mAh cm-2. Based on the advantages of microwave selective and rapid heating, this method creatively realized that the sulfur carrier material was prepared and sulfur was fixed in it at the same time. Therefore, this method would have implications for the preparation of sulfur cathode materials.

Theoretical Insights into Single-Atom Catalysts Supported on N-Doped Defective Graphene for Fast Reaction Redox Kinetics in Lithium-Sulfur Batteries.

Single-atom catalysts are proven to be an effective strategy for suppressing shuttle effect at the source by accelerating the redox kinetics of intermediate polysulfides in lithium-sulfur (Li-S) batteries. However, only a few 3d transition metal single-atom catalysts (Ti, Fe, Co, Ni) are currently applied for sulfur reduction/oxidation reactions (SRR/SOR), which remains challenging for screening new efficient catalysts and understanding the relationship between structure-activity of catalysts. Herein, N-doped defective graphene (NG) supported 3d, 4d, and 5d transition metals are used as single-atom catalyst models to explore electrocatalytic SRR/SOR in Li-S batteries by using density functional theory calculations. The results show that M1 /NG (M1 = Ru, Rh, Ir, Os) exhibits lower free energy change of rate-determining step and Li2 S decomposition energy barrier, which significantly enhance the SRR and SOR activity compared to other single-atom catalysts. Furthermore, the study accurately predicts the by machine learning based on various descriptors and reveals the origin of the catalyst activity by analyzing the importance of the descriptors. This work provides great significance for understanding the relationships between the structure-activity of catalysts, and manifests that the employed machine learning approach is instructive for theoretical studies of single-atom catalytic reactions.