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1. Template‐Assisted Synthesis of Metallic 1T′‐Sn 0.3 W 0.7 S 2 Nanosheets for Hydrogen Evolution Reaction

   https://doi.org/10.1002/adfm.201906069  

   Shao, Gonglei ; Xue, Xiong‐Xiong ; Wu, Binbin ; Lin, Yung‐Chang ; Ouzounian, Miray ; Hu, Travis Shihao ; Xu, Yeqing ; Liu, Xiao ; Li, Shisheng ; Suenaga, Kazu ; et al ( November 2019 , Advanced Functional Materials)

   Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn_1−xW_xS₂alloys can be formed by combining W with 1T tin disulfide (SnS₂) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn_1−xW_xS₂alloys with varyingxare prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn_0.3W_0.7S₂displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn_0.3W_0.7S₂has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn_0.3W_0.7S₂coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS₂. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging heteroatoms to achieve synthetic metastable phase 2D LMDs that have a significantly improved HER catalytic performance.

    

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2. A BF 3 ‐Doped MXene Dual‐Layer Interphase for a Reliable Lithium‐Metal Anode

   https://doi.org/10.1002/adma.202210111  

   Shang, Mingwei ; Shovon, Osman Goni ; Wong, Francis En Yoong ; Niu, Junjie ( December 2022 , Advanced Materials)

   A dual‐layer interphase that consists of an in‐situ‐formed lithium carboxylate organic layer and a thin BF₃‐doped monolayer Ti₃C₂MXene on Li metal is reported. The honeycomb‐structured organic layer increases the wetting of electrolyte, leading to a thin solid electrolyte interface (SEI). While the BF₃‐doped monolayer MXene provides abundant active sites for lithium homogeneous nucleation and growth, resulting in about 50% reduced thickness of inorganic‐rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells is received. The functional BF₃ groups, along with the excellent electronic conductivity and smooth surface of the MXene, greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite‐free lithium‐metal anode. The battery with this dual‐layer coated lithium metal as the anode displays greatly improved electrochemical performance. A high capacity‐retention of 175.4 mAh g⁻¹at 1.0 C is achieved after 350 cycles. In a pouch cell with a capacity of 475 mAh, the battery still exhibits a high discharge capacity of 165.6 mAh g⁻¹with a capacity retention of 90.2% after 200 cycles. In contrast to the fast capacity decay of pure Li metal, the battery using NCA as the cathode also displays excellent capacity retention in both coin and pouch cells. The dual‐layer modified surface provides an effective approach in stabilizing the Li‐metal anode.

    

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3. Multi‐Interface‐Modulated CoS 2 @MoS 2 Nanoarrays Derived by Predesigned Germanomolybdate Polymer Showing Ultrahighly Electrocatalytic Activity for Hydrogen Evolution Reaction in Wide pH Range

   https://doi.org/10.1002/admi.202000780  

   Hou, Yan ; Pang, Haijun ; Xin, Jianjiao ; Ma, Huiyuan ; Li, Bonan ; Wang, Xinming ; Tan, Lichao ( August 2020 , Advanced Materials Interfaces)

   The development of non‐noble metal materials for efficient hydrogen evolution reaction (HER) in wide pH range is still a challenge at present. Herein, a predesigned polyoxometalate (POM)‐based metal–organic polymer {L₃Co₂ · 6H₂O}[H₃GeMo₁₂O₄₀] · 9H₂O (L = 1,2,4‐triazole) is employed as bimetallic source together with thiourea converting to CoS₂@MoS₂on carbon cloth (CC) (abbreviated to CoS₂@MoS₂@CC) for the first time. Impressively, the CoS₂@MoS₂in the form of vertically interconnected nanoarrays with multiple interfaces are grown in situ on CC and act as electrodes directly for HER. The CoS₂@MoS₂@CC‐30h composite exhibits superb activity and long‐durability in both acidic and alkaline media. Low overpotential is achieved in 0.5mH₂SO₄(65 mV) and 1.0mKOH (87 mV) for 10 mA cm⁻²versus RHE, which overmatch major MoS₂‐/POM‐based electrocatalysts. This work therefore may shed substantial lights on designing active and durable molybdenum‐based bi‐/polymetallic sulfide from variable POM‐based metal–organic polymers for electrocatalytic hydrogen evolution reaction in wide pH range.

    

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4. Boosting Hydrogen Evolution Performance of MoS 2 by Band Structure Engineering

   https://doi.org/10.1002/admi.201700303  

   Li, Jing ; Kang, Jiahao ; Cai, Qian ; Hong, Wenting ; Jian, Chuanyong ; Liu, Wei ; Banerjee, Kaustav ( July 2017 , Advanced Materials Interfaces)

   Molybdenum sulfide (MoS₂) has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER) owing to its high activity and stability during the reaction. However, the efficiency of hydrogen production is limited by the number of active sites in MoS₂. In this work, a simple method of fabricating polycrystalline multilayer MoS₂on Mo foil for efficient hydrogen evolution is demonstrated by controlling the sulfur (S) vacancy concentration, which can introduce new bands and lower the hydrogen adsorption free energy (ΔG_H). For the first time, theoretical and experimental results show that the HER performance of synthesized MoS₂with S vacancy can be further enhanced by the very small amount of platinum (Pt) decoration, which can introduce new gap states and more catalytic sites in real space with suitable free energy. The fabricated hybrid electrocatalyst exhibits significantly smaller Tafel slope of 38 mV dec⁻¹and better HER electrocatalytic activity compared to previous works. This approach provides a simple pathway to design low‐cost, efficient and sizable hydrogen‐evolving electrode by simultaneously tuning the MoS₂band structure and active sites.

    

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5. Theoretical and Experimental Insight into the Effect of Nitrogen Doping on Hydrogen Evolution Activity of Ni 3 S 2 in Alkaline Medium

   https://doi.org/10.1002/aenm.201703538  

   Kou, Tianyi ; Smart, Tyler ; Yao, Bin ; Chen, Irwin ; Thota, David ; Ping, Yuan ; Li, Yat ( March 2018 , Advanced Energy Materials)

   Nickel sulfide (Ni₃S₂) is a promising hydrogen evolution reaction (HER) catalyst by virtue of its metallic electrical conductivity and excellent stability in alkaline medium. However, the reported catalytic activities for Ni₃S₂are still relatively low. Herein, an effective strategy to boost the H adsorption capability and HER performance of Ni₃S₂through nitrogen (N) doping is demonstrated. N‐doped Ni₃S₂nanosheets achieve a fairly low overpotential of 155 mV at 10 mA cm⁻²and an excellent exchange current density of 0.42 mA cm⁻²in 1.0mKOH electrolyte. The mass activity of 16.9 mA mg⁻¹and turnover frequency of 2.4 s⁻¹obtained at 155 mV are significantly higher than the values reported for other Ni₃S₂‐based HER catalysts, and comparable to the performance of best HER catalysts in alkaline medium. These experimental data together with theoretical analysis suggest that the outstanding catalytic activity of N‐doped Ni₃S₂is due to the enriched active sites with favorable H adsorption free energy. The activity in the Ni₃S₂is highly correlated with the coordination number of the surface S atoms and the charge depletion of neighbor Ni atoms. These new findings provide important guidance for future experimental design and synthesis of optimal HER catalysts.

    

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