Construction of Fe7Se8@Carbon nanotubes with enhanced sodium/potassium storage

Electrocatalytic reduction of N2 to NH3 by MIL-88-derived pod-like Fe7Se8/C nanomaterials under ambient conditions

In this paper, pod-like Fe7Se8/C nanocomposite catalyst materials were prepared by MIL-88 selenide annealing and the as-prepared Fe7Se8/C nanocatalyst exhibited excellent electrocatalytic performance in neutral electrolyte for the electrocatalytic nitrogen reduction reaction (eNRR). The average ammonia yield rate was 7.11 μg h-1 mgcat-1 with a corresponding faradaic efficiency (FE) of 10.44% obtained at the optimum potential of -0.3 V. Moreover, the as-prepared Fe7Se8/C electrocatalyst shows good selectivity and stability for the eNRR.

Semi-Coherent Heterointerface Engineering via In Situ Phase Transition for Enhanced Sodium/Lithium-Ions Storage

To improve ion transport kinetics and electronic conductivity between the different phases in sodium/lithium-ion battery (LIB/SIB) anodes, heterointerface engineering is considered as a promising strategy due to the strong built-in electric field. However, the lattice mismatch and defects in the interphase structure can lead to large grain boundary resistance, reducing the ion transport kinetics and electronic conductivity. Herein, monometallic selenide Fe3Se4-Fe7Se8 semi-coherent heterointerface embedded in 3D connected Nitrogen-doped carbon yolk-shell matrix (Fe3Se4-Fe7Se8@NC) is obtained via an in situ phase transition process. Such semi-coherent heterointerface between Fe3Se4 and Fe7Se8 shows the matched interfacial lattice and strong built-in electric field, resulting in the low interface impedance and fast reaction kinetics. Moreover, the yolk-shell structure is designed to confine all monometallic selenide Fe3Se4-Fe7Se8 semi-coherent heterointerface nanoparticles, improving the structural stability and inhibiting the volume expansion effect. In particular, the 3D carbon bridge between multi-yolks shell structure improves the electronic conductivity and shortens the ion transport path. Therefore, the efficient reversible pseudocapacitance and electrochemical conversion reaction are enabled by the Fe3Se4-Fe7Se8@NC, leading to the high specific capacity of 439 mAh g-1 for SIB and 1010 mAh g-1 for LIB. This work provides a new strategy for constructing heterointerface of the anode for secondary batteries.

Progress and perspectives on iron-based electrode materials for alkali metal-ion batteries: a critical review

Iron-based materials with significant physicochemical properties, including high theoretical capacity, low cost and mechanical and thermal stability, have attracted research attention as electrode materials for alkali metal-ion batteries (AMIBs). However, practical implementation of some iron-based materials is impeded by their poor conductivity, large volume change, and irreversible phase transition during electrochemical reactions. In this review we critically assess advances in the chemical synthesis and structural design, together with modification strategies, of iron-based compounds for AMIBs, to obviate these issues. We assess and categorize structural and compositional regulation and its effects on the working mechanisms and electrochemical performances of AMIBs. We establish insight into their applications and determine practical challenges in their development. We provide perspectives on future directions and likely outcomes. We conclude that for boosted electrochemical performance there is a need for better design of structures and compositions to increase ionic/electronic conductivity and the contact area between active materials and electrolytes and to obviate the large volume change and low conductivity. Findings will be of interest and benefit to researchers and manufacturers for sustainable development of advanced rechargeable ion batteries using iron-based electrode materials.

Structural regulation enabled stable hollow molybdenum diselenide nanosheet anode for ultrahigh energy density sodium ion pouch cell

For the continued use of sodium-ion batteries (SIBs), which require matching anode materials, it is crucial to create high energy density energy storage devices. Here, hollow nanoboxes shaped carbon supported sulfur-doped MoSe2 nanosheets (S-MoSe2@NC) are fabricated by in situ growth and heterodoping strategy. This ensures that the MoSe2 nanosheets are tightly anchored to the nanoboxes carbon, and the structure can effectively buffer the volume stress caused by sodium ion (de)intercalation, as well as providing abundant ion/electron migration transportations. As anode for SIBs, the S-MoSe2@NC shows a higher rate capability and excellent cycling stability (431.1 mAh/g after 1100 cycles at 10 A/g). This excellent cycle life and high rate ability are due to the structural stability and outstanding electronic conductance with reduced band gap of the S-MoSe2@NC, as evidenced by the diffusion analysis and theoretical calculation. In order to promote the application of SIBs, the S-MoSe2@NC and NaNi1/3Fe1/3Mn1/3O2 were assembled into a pouch cell, and the test found that besides the excellent cycle rate performance, the ultrahigh energy density of 256 Wh kg-1 and flexible characteristics can be achieved. This study has proven that building a structure with a rock-steady foundation and quick ion migration may efficiently control sodium storage and pave the way for novel applications of high-performance transition metal dichalcogenides in sodium storage.

Construction of Porous Carbon Nanosheet/Cu2S Composites with Enhanced Potassium Storage

Porous C nanosheet/Cu2S composites were prepared using a simple self-template method and vulcanization process. The Cu2S nanoparticles with an average diameter of 140 nm are uniformly distributed on porous carbon nanosheets. When used as the anode of a potassium-ion battery, porous C nanosheet/Cu2S composites exhibit good rate performance and cycle performance (363 mAh g-1 at 0.1 A g-1 after 100 cycles; 120 mAh g-1 at 5 A g-1 after 1000 cycles). The excellent electrochemical performance of porous C nanosheet/Cu2S composites can be ascribed to their unique structure, which can restrain the volume change of Cu2S during the charge/discharge processes, increase the contact area between the electrode and the electrolyte, and improve the electron/ionic conductivity of the electrode material.