Shielded SnS2/SnS heterostructures on three-dimensional graphene framework for high-rate and stable sodium-ion storage

Synergism of Hydrogen-Induced Interstitial Effect and Gold-Induced Alloying Effect in PdAuH Metallene for Urea Electrosynthesis from Nitrate and Carbon Dioxide

Urea is a common agricultural fertilizer and industrial raw material, but at present, the traditional industrial production of urea is energy-and pollution-intensive. Electrocatalytic coupling of CO2 and ubiquitous nitrogen sources to synthesize urea is considered as a promising alternative method but requiring high-performance catalysts to boost the C-N coupling electrocatalysis process. Herein, hydrogen-intercalated Pd-Au bimetallene (PdAuHene) was prepared by a three-step method and used for electrosynthesis of urea from NO3- and CO2, deriving an optimum urea Faradaic efficiency of 33.88% and yield rate of 6.68 mmol g-1 h-1 at an applied potential of -0.6 V vs RHE. Detailed material characterizations and electrochemical studies reveal that the metallene structure with ultrathin thickness could improve atomic utilization of precious metal atoms, and the introduction of Au and H atoms could adjust the electronic structure of Pd atoms, regulate the evolution pathway of key N-/C-intermediates, and promote the C-N coupling to form urea.

SnS/SnS2 Heterostructures Embedded in Hierarchical Porous Carbon as Polysulfides Immobilizer for High-Performance Lithium-Sulfur Batteries

Driven by the strong adsorptive and catalytic ability of metal sulfides for soluble polysulfides, it is considered as a potential mediator to resolve the problems of shuttle effect and slow reaction kinetics of polysulfides in lithium-sulfur (Li-S) batteries. However, their further development is limited by poor electrical conductivity and bad long-term durability. Herein, one type of new catalyst composed of SnS/SnS2 heterostructures on hierarchical porous carbon (denoted as SnS/SnS2-HPC) by a simple hydrothermal method is reported and used as an interlayer coating on the conventional separator for blocking polysulfides. The SnS/SnS2-HPC integrates the advantages of a porous conductive network for promoting the transport of electrons and an enhanced electrocatalyst for accelerating polysulfides conversion. As a result, such a cell coupled with a SnS/SnS2-HPC interlayer exhibits a long-term lifespan of 1200 cycles. This work provides a new cell configuration by using heterostructures with a built-in electric field formed from a p-n heterojunction to improve the performance of Li-S batteries.

Quantum dot heterostructures on N-doped graphene with accelerated diffusion kinetics for stable lithium-ion storage

The high energy density and low self-discharge rate of lithium-ion batteries make them promising for large-scale energy storage. However, the practical development of such electrochemical energy storage systems relies heavily on the development of anode materials with high multiplier capacity and stable cycle life. Here, a simple and efficient one-step hydrothermal method is used to obtain stannide heterostructures, which are loaded on N-doped graphene (SnS2/SnO2@NG) that promotes Li+ diffusion for fast charge transfer. It is demonstrated that the built-in electric field generated by the electron transfer from electron-rich SnS2 to SnO2 in the stannide heterojunction collectively provides abundant cation adsorption sites, accelerating the migration of Li+ thus improving the electrochemical reaction kinetics. Besides, the SnS2/SnO2 nanoparticles have high structural stability, and the heterojunction compressive stresses obtained from density functional theory (DFT) calculations can significantly limit the structural damage. When applied as anodes in Li+ batteries with 300 cycles at 0.5 A/g, we achieved a high reversible capacity of 892.73 mAh/g. The rational design of low-cost batteries for energy storage and conversion can benefit from the quantitative design of fast and persistent charge transfer in a stannide heterostructure.

Trapping Lithium Selenides with Evolving Heterogeneous Interfaces for High-Power Lithium-Ion Capacitors

Transition metal selenides anodes with fast reaction kinetics and high theoretical specific capacity are expected to solve mismatched kinetics between cathode and anode in Li-ion capacitors. However, transition metal selenides face great challenges in the dissolution and shuttle problem of lithium selenides, which is the same as Li-Se batteries. Herein, inspired by the density functional theory calculations, heterogeneous can enhance the adsorption of Li₂ Se relative to single component selenide electrodes, thus inhibiting the dissolution and shuttle effect of Li₂ Se. A heterostructure material (denoted as CoSe₂ /SnSe) with the ability to evolve continuously (CoSe₂ /SnSe→Co/Sn→Co/Li₁₃ Sn₅ ) is successfully designed by employing CoSnO₃ -MOF as a precursor. Impressively, CoSe₂ /SnSe heterostructure material delivers the ultrahigh reversible specific capacity of 510 mAh g^-1 after 1000 cycles at the high current density of 4 A g^-1 . In situ XRD reveals the continuous evolution of the interface based on the transformation and alloying reactions during the charging and discharging process. Visualizations of in situ disassembly experiments demonstrate that the continuously evolving interface inhibits the shuttle of Li₂ Se. This research proposes an innovative approach to inhibit the dissolution and shuttling of discharge intermediates (Li₂ Se) of metal selenides, which is expected to be applied to metal sulfides or Li-Se and Li-S energy storage systems.

Multi-heterostructured SnO2/SnSx embedded in carbon framework for high-performance sodium-ion storage

Heterostructure materials, as newborn electrode materials for rechargeable batteries, are attracting increasing attention due to their robust architectures and superior electrochemical performances. It is widely believed that the inner electric field induced at the interface can improve the electric conductivity and ion diffusion kinetics, thus enhancing the long-term stability and high-rate performance of the batteries. Although much progress is made on heterostructure construction, the performance of the batteries is still far from satisfying the commercial applications. In this work, a new type of SnO₂/SnS_x (x = 1, 1.5) heterostructure embedded in carbon framework (C@SnO₂/SnS_x) is constructed via a facile sulfidation process. Compared to a single heterojunction, the multi-heterojunctions generated at SnO₂/SnS_x interface can induce an intensified built-in electric field, which promotes charge transportation and reaction kinetics of the electrode for Na-ions storage. Upon the sodiation process, the induced intensified electric field drives Na ions from Sn₂S₃ or SnO₂ to SnS, while an inverse transportation of Na ions are accelerated upon the desodation process. As a result, C@SnO₂/SnS_x exhibits an outstanding reversible capacity of 510 mA h g^-1 after 300 cycles at 200 mA g^-1.

Desulfurization-Induced Formation of Amorphized Substoichiometric Tin Sulfide for Super High-Rate Capacity and Degradation-Free Cycling of Na Ion Storage

This work reports an amorphization and partial desulfurization method to improve the performance of sulfide-based materials for Na⁺ storage. Specifically, the polypyrrole derived carbon coated amorphous substoichiometric tin sulfide supported on aminated carbon nanotubes (PPY-C@SnS_x /ACNTs) with amorphized and substoichiometric tin sulfide (SnS_x ) is synthesized by simply thermal annealing the PPY-C@SnS₂ /ACNTs. The PPY-C@SnS_x /ACNTs shows stable reversible capacities of 410.2 mAh g^-1 for Na⁺ storage at 0.1 A g^-1 and excellent rate capacities of 270.2, 235.5, 217.4, and 210.0 mAh g^-1 at 5.0, 10.0, 20.0, and 30.0 A g^-1 , respectively. Nearly zero drops on the reversible capacities can be observed when it is sodiated/desodiated at 2.0, 5.0, and 10.0 A g^-1 for up to 1000, 6500, 8000 cycles, respectively. Its outstanding rate capacities and degradation-free cycling stabilities mainly arise from the amorphized and substoichiometric structure of SnS_x , which improve the reversible capacities and Na⁺ diffusivities of the PPY-C@SnS_x /ACNTs. The density functional theory (DFT) calculations indicate that the partial desulfurization can improve the electric conductivity and promote the sodiation/desodiation of SnS_x . It explains why the PPY-C@SnS_x /ACNTs can exhibit high performance for Na⁺ storage well.

Vertical 2-dimensional heterostructure SnS-SnS2 with built-in electric field on rGO to accelerate charge transfer and improve the shuttle effect of polysulfides

Traditional carbon materials as sulfur hosts of Li-sulfur(Li-S) cathodes have slightly physical constraint for polysulfides, due to their no-polar property. Therefore, it is necessary to further enhance the affinity between sulfur hosts and polysulfides, and relieve the shuttle effects in the Li- S batteries. Herein, we report a novel vertical 2-dimensional (2D) p-SnS/n-SnS₂ heterostructure sheets which grown on the surface of rGO. The excellent electrochemical properties of SnS-SnS₂@rGO as Li-S cathode are ascribed to the stronger absorption effect of metal sulphides for polysulfides and the smooth trapping-diffusion-conversion effect of p-SnS/n-SnS₂ heterostructure for polysulfides. As a conductive carrier for the growth of vertical 2D p-SnS/n-SnS₂ heterostructure nanosheets, rGO can protect the steadiness and enhance the cycle stability of electrode, compared with heterostructure without rGO. In addition, the built-in electric field in the 2D p-SnS/n-SnS₂ heterostructure during the discharge/charge processes can effectively accelerate charge transfer, and the charge transfer mechanism in SnS-SnS₂ heterostructure during cycling has been investigated. At a rate capability of 2C, the designed SnS-SnS₂@rGO as Li-S cathode delivers high specific capacities of 907 mAh g^-1 and 571 mAh g^-1 after the first cycle and 500 cycles, respectively, which shown excellent cycling ability.

Bimetallic Sulfide SnS2/FeS2 Nanosheets as High-Performance Anode Materials for Sodium-Ion Batteries

Transition-metal sulfide SnS₂ has aroused wide concern due to its high capacity and nanosheet structure, making it an attractive choice as the anode material in sodium-ion batteries. However, the large volume expansion and poor conductivity of SnS₂ lead to inferior cycle stability as well as rate performance. In this work, FeS₂ was in situ introduced to synchronously grow with SnS₂ on rGO to prepare a heterojunction bimetallic sulfide nanosheet SnS₂/FeS₂/rGO composite. The composition and distinctive structure facilitate the rapid diffusion of Na⁺ and improve the charge transfer at the heterogeneous interface, providing sufficient space for volume expansion and improving anode materials' structural stability. SnS₂/FeS₂/rGO bimetallic sulfide electrode boasts a capacity of 768.3 mA h g^-1 at the current density of 0.1 A g^-1, and 541.2 mA h g^-1 at the current density of 1 A g^-1 in sodium-ion batteries, which is superior to that of either single metal sulfide SnS₂ or FeS₂. TDOS calculation further confirms that the binding of FeS₂/SnS₂-Na is more stable than FeS₂ and SnS₂ alone. The superior electrochemical performance of the SnS₂/FeS₂/rGO composite material makes it a promising candidate for sodium storage.

Coupling SnS2 and rGO aerogel to CuS for enhanced light-assisted OER electrocatalysis

In order to harvest more light wavelengths to improve the light-assisted electrochemical water splitting capacity, we developed a novel heterostructure of three-dimensional (3D) flower-like CuS architecture with accompanying SnS2 nanoparticles and reduced graphene oxide (rGO) aerogel for outstanding light-assisted electrocatalytic OER performance and good stability. The excellent catalytic kinetics, effective capturing of visible light, and rapid charge transfer of the CuS/SnS2/rGO (CSr) heterostructure were demonstrated. The overpotential (264 mV@10 mA cm-2) under light-assisted conditions is 20% lower than that under light-chopped conditions. SnS2 can harvest more light wavelengths and this boosts its intrinsic activity. However, with the increase of the SnS2 content, the OER activity decreases. The combination of the CS heterostructure and the rGO conductive aerogel achieves rapid charge transfer. Furthermore, the possible mechanism of the light-assisted electrocatalytic OER was also proposed. Overall, this work provides new insights into the simple and scalable fabrication of a highly efficient, low-cost, and stable non-noble-metal-based electrocatalyst.