Recent advances in defect-engineered molybdenum sulfides for catalytic applications

Dual functional coordination interactions enable fast polysulfide conversion and robust interphase for high-loading lithium-sulfur batteries

The stable operation of high-capacity lithium-sulfur batteries (LSBs) has been hampered by slow conversion kinetics of lithium polysulfides (LiPSs) and instability of the lithium metal anodes. Herein, 6-(dibutylamino)-1,3,5-triazine-2,4-thiol (DTD) is introduced as a functional additive for accelerating the kinetics of cathodic conversion and modulating the anode interface. We proposed that a coordination interaction mechanism drives the polysulfide conversion and modulates the Li+ solvated structure during the binding of the N-active site of DTD to LiPSs and lithium salts. The results show that DTD effectively promotes the redox of LiPSs and the formation of an inorganic-organic synergistic solid electrolyte interface (SEI). This suppresses the parasitic reaction of LiPSs and confers uniform lithium deposition. Therefore, the capacity decay rate per cycle of the DTD-added LSBs is only 0.066% after 600 cycles at 1C. Moreover, Li-Li symmetric batteries exhibited smaller overpotentials during long cycling and a 41% increment in cycle life. Even with high sulfur loading (5.38 mg cm-2) and a depleted electrolyte sulfur ratio (E/S = 5 μL mg-1), the capacity retention of the battery is 71.5%. This work provides a new reference for elucidating the mechanisms of polysulfide conversion and SEI interface regulation for high-energy-density lithium-sulfur batteries.

Long-life graphite-lithium sulfide full cells enabled through a solvent Co-intercalation-free electrolyte design

Graphite (Gr) is the predominant anode material for current lithium-ion technologies. The Gr anode could offer a practical pathway for the development of lithium-sulfur (Li-S) batteries due to its superior stability and safety compared to Li-metal. However, Gr anodes are not compatible with the conventional dilute ether-based electrolytes typically used in Li-S systems. Here, an optimized ether electrolyte is presented, utilizing 1 M lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) in 1,3-dioxolane (DOL)/1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (TTE). Without altering the salt concentration, this electrolyte regulates the solvation structure and promotes the formation of a robust solid-electrolyte interphase (SEI) layer, leading to a significant improvement in the cyclability of Gr anodes. Meanwhile, the DOL/TTE electrolyte maintains adequate kinetics for the sulfur cathode, enabling its pairing with Gr anodes without any cathode modification. The cell with a Gr anode delivers a reversible discharge capacity of 515 mA h g-1 after 400 cycles at C/10 rate, in contrast to only 143 mA h g-1 for the Li-metal anode cell. Moreover, a Gr || Li2S full cell with a negative-to-positive capacity (N/P) ratio of 1.05 and a Li2S loading of 3 mg cm-2 shows a stable 58% capacity retention after 400 cycles.

Modification Strategies for Development of 2D Material-Based Electrocatalysts for Alcohol Oxidation Reaction

2D materials, such as graphene, MXenes (metal carbides and nitrides), graphdiyne (GDY), layered double hydroxides, and black phosphorus, are widely used as electrocatalyst supports for alcohol oxidation reactions (AORs) owing to their large surface area and unique 2D charge transport channels. Furthermore, the development of highly efficient electrocatalysts for AORs via tuning the structure of 2D support materials has recently become a hot area. This article provides a critical review on modification strategies to develop 2D material-based electrocatalysts for AOR. First, the principles and influencing factors of electrocatalytic oxidation of alcohols (such as methanol and ethanol) are introduced. Second, surface molecular functionalization, heteroatom doping, and composite hybridization are deeply discussed as the modification strategies to improve 2D material catalyst supports for AORs. Finally, the challenges and perspectives of 2D material-based electrocatalysts for AORs are outlined. This review will promote further efforts in the development of electrocatalysts for AORs.

Highly efficient hydrodesulfurization driven by an in-situ reconstruction of ammonium/amine intercalated MoS2 catalysts

Hydrodesulfurization (HDS) is a commonly used route for producing clean fuels in modern refinery. Herein, ammonium/amine-intercalated MoS2 catalysts with various content of 1T phase and S vacancies have been successfully synthesized. Along with the increment of 1T phase and S vacancies of MoS2, the initial reaction rate of the HDS of dibenzothiophene (DBT) can be improved from 0.09 to 0.55 μmol·gcat-1·s-1, accounting for a remarkable activity compared to the-state-of-the-art catalysts. In a combinatory study via the activity evaluation and catalysts characterization, we found that the intercalation species of MoS2 played a key role in generating more 1T phase and S vacancies through the 'intercalation-deintercalation' processes, and the hydrogenation and desulfurization of HDS can be significantly promoted by 1T phase and S vacancies on MoS2, respectively. This study provides a practically meaningful guidance for developing more advanced HDS catalysts by the intercalated MoS2-derived materials with an in-depth understanding of structure-function relationships.