Energy Barrier For Decomposition Research Articles

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.

Tetraiodo nickel phthalocyanine electrocatalyst enables superior Na–Se battery performances by enhancing the utilization of Na2Se

Sodium–Selenium (Na–Se) batteries are regarded as one of the most promising alternative energy storage devices compared to their room-temperature sodium-sulfur battery counterparts. Since Selenium cathodes operate well in carbonate-based electrolytes, the solubility issue of polyselenides is no longer an issue. However, the main obstacles of Na–Se batteries remain the precipitation and reoxidation of sodium selenide (Na2Se) owing to the high energy barrier of these reactions and passivation of the electrode during cycling. Herein, we propose a tetraiodo nickel phthalocyanine (NiPc) electrocatalyst to improve the electrochemical performance of Na–Se batteries. It is demonstrated that the presence of even a small amount of NiPc improves the electrocatalytic conversion of Na2Se by lowering the decomposition energy barrier of Na2Se. The improved cell performances are verified by the decrease in reaction polarization, Tafel slope values, and the measured internal resistance of Na–Se cells in addition to the density functional theory (DFT) calculations. Consequently, the Na–Se cell with the NiPc electrocatalyst exhibited outstanding rate capability (405 mAh∙g−1 after 250 cycles at 3375 mA g−1 and superior long-term cyclic stability (563 mAh∙g−1 after 250 cycles at 675 mA g−1), which are among the most promising rate performance characteristics demonstrated in the literature.

Lattice‐Asymmetry‐Driven Selective Area Sublimation: A Promising Strategy for III‐Nitride Nanostructure Tailoring

Lattice‐asymmetry‐driven selective area sublimation (SAS) process of GaN is systemically investigated by exploring the in situ dynamic evolution of the decomposition pathway under ultra‐high vacuum. The rationale of the SAS is confirmed as a strong anisotropic decomposition driven by lattice‐asymmetry of wurtzite crystal: the sublimation preferably starts along the ‐c axis due to the relatively lower decomposition energy barrier. Finally, the fabrication of site‐ and size‐controlled GaN nanowires has been achieved by utilizing the SAS process, exhibiting good controllability on the sidewall of nanowires. These findings shed light on the thermodynamic mechanism of the lattice‐asymmetry‐driven sublimation process in III‐nitrides, providing an efficient alternative approach for the tailoring of semiconductor micro/nanostructures.

Constructing Molybdenum Phosphide@Cobalt Phosphide Heterostructure Nanoarrays on Nickel Foam as a Bifunctional Electrocatalyst for Enhanced Overall Water Splitting.

The construction of multi-level heterostructure materials is an effective way to further the catalytic activity of catalysts. Here, we assembled self-supporting MoS2@Co precursor nanoarrays on the support of nickel foam by coupling the hydrothermal method and electrostatic adsorption method, followed by a low-temperature phosphating strategy to obtain Mo4P3@CoP/NF electrode materials. The construction of the Mo4P3@CoP heterojunction can lead to electron transfer from the Mo4P3 phase to the CoP phase at the phase interface region, thereby optimizing the charge structure of the active sites. Not only that, the introduction of Mo4P3 will make water molecules preferentially adsorb on its surface, which will help to reduce the water molecule decomposition energy barrier of the Mo4P3@CoP heterojunction. Subsequently, H* overflowed to the surface of CoP to generate H2 molecules, which finally showed a lower water molecule decomposition energy barrier and better intermediate adsorption energy. Based on this, the material shows excellent HER/OER dual-functional catalytic performance under alkaline conditions. It only needs 72 mV and 238 mV to reach 10 mA/cm2 for HER and OER, respectively. Meanwhile, in a two-electrode system, only 1.54 V is needed to reach 10 mA/cm2, which is even better than the commercial RuO2/NF||Pt/C/NF electrode pair. In addition, the unique self-supporting structure design ensures unimpeded electron transmission between the loaded nanoarray and the conductive substrate. The loose porous surface design is not only conducive to the full exposure of more catalytic sites on the surface but also facilitates the smooth escape of gas after production so as to improve the utilization rate of active sites. This work has important guiding significance for the design and development of high-performance bifunctional electrolytic water catalysts.

Boosting polysulfide confinement and redox kinetics via ZnSe/NC@rGO as separator modifier for high-performance lithium-sulfur batteries

Although lithium-sulfur (Li-S) batteries have an unparalleled specific capacity, the notorious shuttle effect, and slow reaction kinetics severely inhibit their development. Herein, a composite composed of ZnSe nanoparticles with a nitrogen-doped (N-doped) carbon shell uniformly dispersed in reduced graphene oxide (ZnSe/NC@rGO) is designed as a separator modifier for Li-S batteries. The underlying mechanism of the ZnSe/NC@rGO modified separator is confirmed by both systemic electrochemical characterization and density functional theory (DFT) calculations. Graphene as a highly conductive skeleton promotes electrical conductivity, while N-doping provides additional adsorption sites for the immobilization of lithium polysulfides (LiPSs). Moreover, the polar ZnSe has good chemical adsorption capabilities for LiPSs and could lower the decomposition energy barrier of Li2S, which effectively facilitates the catalytic conversion of polysulfides. In addition, the separator modifier is beneficial to the uniform deposition of lithium. Thus, the delicate catalyst can effectively suppress the shuttle effect and accelerate the redox reaction kinetics during the charging and discharging processes. When used as a separator modifier of Li-S batteries, ZnSe/NC@rGO delivers enhanced electrochemical performance, including a high capacity (1057 mAh g–1 at 0.2 C after 100 cycles) and excellent rate performance of 685 mAh g–1 at 3 C. The negligible capacity decay per cycle within 900 cycles at 1 C is as low as 0.043%. These findings not only provide a feasible method for boosting the electrochemical performance of Li-S batteries but also reveal that transition metal selenides have potential in energy storage as electrocatalysts.

A computational study on bifunctional 1T-MnS2 with an adsorption-catalysis effect for lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are promising rechargeable energy storage systems with a high energy density, environmental friendliness and low cost. However, the commercialization process of Li-S batteries has been seriously hindered by the shuttling of lithium polysulfides (LiPSs) and the sluggish kinetics of conversion reaction among sulfur species. In this work, the adsorption-catalysis performance of five transition metal disulfide 1T-MS2 (M = Mn, V, Ti, Zr, and Hf) surfaces is investigated by evaluating the adsorption energy of sulfur species, Li-ion diffusion energy barrier, decomposition energy barrier of Li2S, and the Gibbs free energy barrier of the sulfur reduction reaction based on first-principles calculations. Our results show that the sulfiphilicity of 1T-MS2 plays an important role in the adsorption behavior of short-chain sulfur species, in addition to lithiophilicity. Remarkably, among the five 1T-MS2 materials, our results confirm that 1T-TiS2 and 1T-VS2 show excellent adsorption-catalysis performance and it is predicted that 1T-MnS2 is an even better candidate catalyst to inhibit the shuttle effect and accelerate delithiation/lithiation kinetics. Moreover, the outstanding performance of 1T-MnS2 persists in a solvent environment and under strain modulation. Our results not only demonstrate that 1T-MnS2 is an excellent potential catalyst for high-performance Li-S batteries, but also provide great insights into the adsorption-catalysis mechanism during the cycling process.

Selectivity dependence of atomic layer deposited manganese oxide on the precursor ligands on platinum facets

Selective atomic layer deposition shows a great perspective on the downscaling manufacturing of nanoelectronics with high precision. The interaction between Mn precursors and Pt terrace, (100), and (111) facets is investigated by density functional theory and microkinetic modeling to reveal the effect of the ligands of the precursors on MnOx selective growth on the Pt facets. MnCl2 and MnCp2 have preferential deposition on the Pt terrace and (100) over (111), while Mn(acac)2 does not show obvious selectivity on the three pristine Pt facets due to the extremely strong adsorption energies. It is found that the adsorption energies of the Mn precursors exhibit size dependence mainly due to the van der Waals interaction. The increase in the number of methyl substituents of Cp-derivate precursors enlarges the decomposition energy barrier of the precursor on (100) due to the steric hindrance, which weakens the selectivity between (111) and (100) facets. It is found that the oxygen groups on these facets accelerate the decomposition of the precursors, which diminishes the selectivity of the precursors on the three Pt facets. While the surface hydroxyl groups significantly weaken the adsorption of Mn(acac)2, it exhibits preferential deposition on hydroxylated Pt (111) among the three facets. Our work highlights the group effect on adsorption, reaction kinetics, and the selective growth of Mn precursors on Pt facets, which provides important guidance to screen precursors to achieve selective deposition of metal oxides on differentiated metal surfaces.

Structure evolution of vacancy-hydrogen complexes in a nickel-based single-crystal superalloy

ABSTRACT The structural stability of vacancy-hydrogen complexes at the interface in nickel-based single-crystal superalloy is accessed mainly by calculating the activation energies associated with the evolution of their structures. It is found that the structure evolution and subsequent decomposition of the complex needs little time to be thermally activated at the service temperature of an aeroengine, and misfit dislocations at the interface significantly reduces the energy barrier for decomposition. Therefore, during the creep process, which is more severe at high temperatures, vacancies around misfit dislocations are not expected to enhance hydrogen interfacial segregation, although vacancy-hydrogen complexes are quite stable at room temperature.

Design of transition metal carbonitrides (MCNs) as promising anchoring and high catalytic performance materials for lithium-sulfur batteries

The challenges faced by the application of lithium-sulfur (Li-S) batteries with high specific capacity and high energy density include the shuttle effect, which reduces the rate of sulfur reduction reaction (SRR), the difficulty of decomposition of insoluble Li2S during charging, and poor conductivity during charging and discharging. Herein, the adsorption, catalytic and electrical properties of a new class of two-dimensional transition metal carbonitrides (MCNs) have been systematically investigated as candidate cathodes for Li-S batteries. Density functional theory (DFT) calculations combined with van der Waals (vdW) interaction analysis show that TiCN and VCN can effectively suppress the shuttle effect with different solvents. The analysis of the Gibbs free energy and Li2S decomposition energy barrier of the lithiation process show that TiCN and VCN can significantly accelerate the decomposition of Li2S and sulfur reduction reaction, and improves the battery cycle performance. Moreover, the quantum conductivity (G) and density of state (DOS) of the VCN cathode during the whole charge-discharge process indicate that the electrode always has good conductivity. Based on these advantages, VCN is considered as a potential high-performance cathode material for Li-S batteries. This research has a certain guiding effect on the application of two-dimensional (2D) carbon and nitrogen materials in Li-S batteries.

Platinum Nanocrystals Embedded in Three-Dimensional Graphene for High-Performance Li-O2 Batteries.

Graphene is considered as a promising cathode candidate for Li-O2 batteries because of its excellent electronic conductivity and oxygen adsorption capacity. However, for Li-O2 batteries, the self-stacking effect caused by two-dimensional (2D) structural properties of graphene is not conducive to the rapid oxygen transport and mass transfer process, thereby affecting the electrode kinetics. Here, we successfully prepared three-dimensional (3D) graphene with different scales by plasma-enhanced chemical vapor deposition and physical pulverization strategies, in which CH4 is the carbon source and H2/Ar mixed gas is the etching gas. Meanwhile, we fabricated 3D graphene-based Pt nanocatalysts by an ultraviolet-assisted construction strategy and then applied them in Li-O2 batteries. Systematic studies reveal a special relevance between electrochemical performance and graphene particle size, and the smaller-sized 3D graphene can better maintain the microstructure distribution in both the Pt embedding process and electrochemical applications, which is beneficial to the transport of oxygen and Li ions, lowering the decomposition energy barrier of Li2O2, and further obtaining reduced charge overpotential (0.22 V) and prolonged cycle life for Li-O2 batteries. Finally, we anticipate that this work could promote the practical application of 2D materials and larger-sized 3D materials in Li-O2 batteries.

A Nonaqueous Mg‐CO2 Battery with Low Overpotential

AbstractMg‐CO2 batteries, which exploit the greenhouse gas CO2 as cathode active species, are an appealing next‐generation battery candidate due to their high efficiency energy storage and value‐added CO2 utilization. However, compared with other metal‐CO2 systems, few aprotic Mg‐CO2 batteries have been reported so far as a result of several crucial problems including the comparatively slow redox reaction kinetics, a large decomposition energy barrier of the reduction products, and poor reversibility in their multi‐electron three‐phase cathodic reactions in nonaqueous environments. Herein, a rechargeable Mg‐CO2 battery is developed by using a Mo2C‐CNTs catalytic cathode, a nonaqueous electrolyte, and a magnesium metal anode. The Mo2C‐CNTs catalytic cathode can greatly reduce the charge overpotential of the Mg‐CO2 battery through tuning the CO2 reduction pathways. The results of a variety of ex situ and in situ experiments as well as theoretical calculations show the Mo2C catalyst not only induces surface molecular adsorption for faster reaction kinetics but also improves the selectivity toward MgC2O4 in the CO2 reduction process for a higher Faraday efficiency. An exceptional low voltage hysteresis is achieved for the Mg‐CO2 battery. This work demonstrates a promising strategic option for rechargeable nonaqueous Mg‐CO2 batteries for simultaneously addressing energy and environmental issues.

Dynamic Intercalation–Conversion Site Supported Ultrathin 2D Mesoporous SnO2/SnSe2 Hybrid as Bifunctional Polysulfide Immobilizer and Lithium Regulator for Lithium–Sulfur Chemistry

The practical application of lithium-sulfur batteries is impeded by the polysulfide shuttling and interfacial instability of the metallic lithium anode. In this work, a twinborn ultrathin two-dimensional graphene-based mesoporous SnO2/SnSe2 hybrid (denoted as G-mSnO2/SnSe2) is constructed as a polysulfide immobilizer and lithium regulator for Li-S chemistry. The as-designed G-mSnO2/SnSe2 hybrid possesses high conductivity, strong chemical affinity (SnO2), and a dynamic intercalation-conversion site (LixSnSe2), inhibits shuttle behavior, provides rapid Li-intercalative transport kinetics, accelerates LiPS conversion, and decreases the decomposition energy barrier for Li2S, which is evidenced by the ex situ XAS spectra, in situ Raman, in situ XRD, and DFT calculations. Moreover, the mesoporous G-mSnO2/SnSe2 with lithiophilic characteristics enables homogeneous Li-ion deposition and inhibits Li dendrite growth. Therefore, Li-S batteries with a G-mSnO2/SnSe2 separator achieve a favorable electrochemical performance, including high sulfur utilization (1544 mAh g-1 at 0.2 C), high-rate capability (794 mAh g-1 at 8 C), and long cycle life (extremely low attenuation rate of 0.0144% each cycle at 5 C over 2000 cycles). Encouragingly, a 1.6 g S/Ah-level pouch cell realizes a high energy density of up to 359 Wh kg-1 under a lean E/S usage of 3.0 μL mg-1. This work sheds light on the design roadmap for tackling S-cathode and Li-anode challenges simultaneously toward long-durability Li-S chemistry.

Design of Novel Transition-Metal-Doped C6N2 with High-Efficiency Polysulfide Anchoring and Catalytic Performances toward Application in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are highly expected because of their high theoretical specific capacity and energy density. However, its application still faces challenges, including the shuttle effect affecting the sulfur reduction reaction, the high decomposition energy barrier of Li2S during charging, the volume change of sulfur, and the poor conductivity during charging and discharging. Here, combined with density functional theory and particle swarm optimization algorithm for the nitrogen carbide monolayer structural search (CmN8-m, m = 1-8), the surprising discovery is that a single metal-atom-doped C6N2 monolayer could effectively accelerate the conversion of lithium polysulfide and anchor lithium polysulfide during discharging and decrease the decomposition energy barrier of Li2S during charging. This "anchoring and catalyzing" mechanism effectively reduces the shuttle effect and greatly improves the reaction kinetics. Among a series of metal atoms, Cr is the best doping element, and it exhibits suitable adsorption energy for polysulfides and the lowest decomposition energy barrier for Li2S. This work opens up a new way for the development of transition-metal-doped carbon-nitrogen materials with an excellent catalytic activity for lithium polysulfide as cathode materials for Li-S batteries.

Li-CO2/O2 battery operating at ultra-low overpotential and low O2 content on Pt/CNT catalyst

Li-CO2/O2 battery presents a promising solution to combine CO2 utilization and electrochemical energy storage. Herein, Pt nanoparticles (NPs) of 2.5 nm in mean size loaded uniformly on carbon nanotubes (Pt/CNT) were synthesized and served as cathodic catalysts. The Li-CO2/O2 battery with Pt/CNT catalyst were investigated in mixture gas of CO2 and O2 with O2 content varying from 0% to 20%. It has revealed that the Li-CO2/O2 (2% O2) battery, i.e., operating with 2% O2 content, displays a minimum overpotential of 0.31 V and a cycling stability of 127 cycles, which are significantly superior to the Li-CO2/O2 (20% O2) battery (0.51 V, 90 cycles) and the Li-CO2 battery (0% O2 content) (0.44 V, 110 cycles). Results of in-situ Fourier transform infrared (FTIR) spectroscopy have demonstrated the complete decomposition of Li2CO3 at 3.2 V in the Li-CO2/O2 (2% O2) battery. However, density function theory (DFT) calculations indicate that the decomposition energy barrier of Li2CO3 in Li-CO2/O2 (2% O2) battery is higher than that in Li-CO2 battery. SEM characterizations revealed a localized growth mechanism when O2 content is between 2% and 6% during the initial cycling, in which the Li2CO3 tends to form inside the Pt/CNT catalyst layer, rather than it distributes uniformly on both sides of the Pt/CNT catalyst layer with 0% or 20% O2 content. Such a growth mechanism ensures a better contacting interface between the Pt/CNT catalyst and Li2CO3, which plays a key role in optimal battery performance.

Trade-off effect of 3d transition metal doped boron nitride on anchoring polysulfides towards application in lithium-sulfur battery

Sulfur cathodes in lithium-sulfur batteries (LSBs) suffer from the notorious “shuttle effect”, low sulfur use ratio, and tardy transformation of lithium polysulfides (LiPSs), while using two-dimensional (2D) polar anchoring materials combined with single-atom catalysis is one of the promising methods to address these issues. Herein, the 3d transition metal (TM) doped 2D boron nitrides (BN), labeled as TM-BN, are studied for the anchoring and redox kinetics of LiPSs using first principles calculations. From the simulated results, the TM atom and adjacent N atoms are active adsorption sites for binding S atoms in LiPSs/S8 and Li atoms in LiPSs, respectively. A negative d-band center closer to the Fermi level of TM-BN is key for enhancing the binding strength of TM-S and lowering the Li2S decomposition energy barrier, while it deteriorates the activity of adjacent N atoms. Fortunately, the electrolyte environment has little effect on the superiority of the TM-BN for binding polysulfides/S8, guaranteeing the sturdy anchor of polysulfides/S8 in realistic conditions. The trade-off effect on the activities of TM and adjacent N atom sites in TM-BN for binding LiPSs highlights the excellence of Ti/V/Cr-BN as modification materials for LSB.

High-Index Faceted Nanocrystals as Highly Efficient Bifunctional Electrocatalysts for High-Performance Lithium–Sulfur Batteries

HighlightsHigh-index faceted Fe2O3 nanocrystals with abundant unsaturated Fe sites not only have strong adsorption capacity to anchor LiPSs but also have superior catalytic activity to facilitate the redox conversion of LiPSs and reduce the decomposition energy barrier of Li2S.Our work deepens the comprehending of facet-dependent activity of catalysts in Li–S chemistry and affords a novel perspective for the design of advanced sulfur electrodes.

Crystal Facet Engineering Induced Active Tin Dioxide Nanocatalysts for Highly Stable Lithium–Sulfur Batteries

AbstractControlling exposed crystal facets through crystal facet engineering is an efficient strategy for enhancing the catalytic activity of nanocrystalline catalysts. Herein, the active tin dioxide nano–octahedra enclosed by {332} crystal facets (SnO2 {332}) are synthesized on reduced graphene oxide and demonstrate powerful chemisorption and catalytic ability, accelerating the redox kinetics of sulfur species in lithium–sulfur chemistry. Attributed to abundant unsaturated–coordinated Sn sites on {332} crystal planes, SnO2 {332} has outstanding adsorption and catalytic properties. The material not only adsorbs and converts polysulfides efficiently, but also prominently lowers the decomposition energy barrier of Li2S. The batteries with these high active electrocatalysts exhibit excellent cycling stability with a low capacity attenuation of 0.021% every cycle during 2000 cycles at 2 C. Even with a sulfur loading of 8.12 mg cm−2, the batteries can still cycle stably and maintain a prominent areal capacity of 6.93 mAh cm−2 over 100 cycles. This research confirms that crystal facet engineering is a promising strategy to optimize the performance of catalysts, deepens the understanding of surface structure‐oriented electrocatalysis in Li–S chemistry, while aiding the rational design of advanced sulfur electrodes.

Upcycling Poly(Ethylene Terephthalate): Identification of the Recovered Poly(Ethylene Terephthalate) by Thermogravimetry Analysis

The production and utilization of disposal merchandise made of poly(ethylene terephthalate) (PET) continue to increase with an annual rate of ∼2%. The post-consumer PET (PC-PET), accumulated as waste, creates a pseudo-renewable resource which generates opportunities for reusing and recycling. The recycling of PC-PET saves energy and reduces the burden that the waste plastics in landfills and storage facilities impose on the environment. The polymer of this study (PET-R) was purified from PC-PET by a solvent extraction method and was characterized by thermogravimetric analysis (TGA) via five different linear temperature programs. The TGA curves of PET-R showed three distinct regions: the vaporization of the adsorbed volatile organic chemicals (VOCs) at temperatures 60–220 °C, the fast decomposition of the purified PET (PET-R) 350–500 °C, and the slow pyrolysis of the remains at temperatures >500 °C. The values of decomposition energy barrier (Ea), preexponential of the Arrhenius equation (lnA) and the mechanism of decomposition expressed by f(α), for both VOCs and PC-PET, were evaluated by isoconversional methods according to the Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall methods; the results of the two methods were very close to each other for each of the factors in each of the stages. The values of Ea, and lnA of the VOCs decreased with the increase of the extent of the reaction since they were related to the availability of the VOCs. The values of Ea, and A of PET-R were relatively constant with standard deviations of ±4 kJ/mol. The thermal properties of PET-R were close to the properties reported for the pure PET samples. This proves that pure PET can be extracted and purified from PC-PET by solvent extraction for industrial applications and upcycling wastes.

Regulating polysulfide intermediates by ultrathin Co-Bi nanosheet electrocatalyst in lithium−sulfur batteries

The practical application of lithium–sulfur (Li–S) batteries is hindered by the nonconductivity of sulfur, sluggish reaction kinetics and polysulfide shuttling. The liquid lithium polysulfide intermediates, connecting the Li–S battery electrochemical reaction of sulfur to Li2S, play a decisive role on battery performance. Herein, Co-Bi nanosheets intimately grown on reduced graphene oxides (Co-Bi/rGO) composite has been reported for the first time to regulate the polysulfide intermediates. The Co-Bi could not only chemically trap polysulfides but also propel the acceleration of polysulfide conversion enabled by a lower free energy and decomposition energy barrier in Li–S reaction process. Therefore, the Co-Bi/rGO–S cathode delivers a high capacity of 1334 mAh g–1 at 0.2 C, impressive rate performance up to 8 C, outstanding cycling stability over 500 cycles at 1 C, and remarkable areal capacity of 8.3 mAh cm–2 with a high sulfur mass loading of 9.5 mg cm–2. The chemical binding strength, the Gibbs free energy and the energy barrier for transition state from theoretical calculations give a deep insight of polysulfide regulation by Co-Bi.