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Lithium intercalation of MoS₂is generally believed to introduce a phase transition from H phase (semiconducting) to T phase (metallic). However, during the intercalation process, a spatially sharp boundary is usually formed between the fully intercalated T phase MoS₂and non-intercalated H phase MoS₂. The intermediate state,i.e., lightly intercalated H phase MoS₂without a phase transition, is difficult to investigate by optical-microscope-based spectroscopy due to the narrow size. Here, we report the stabilization of the intermediate state across the whole flake of twisted bilayer MoS₂. The twisted bilayer system allows the lithium to intercalate from the top surface and enables fast Li-ion diffusion by the reduced interlayer interaction. TheE_2gRaman mode of the intermediate state shows a peak splitting behavior. Our simulation results indicate that the intermediate state is stabilized by lithium-induced symmetry breaking of the H phase MoS₂. Our results provide an insight into the non-uniform intercalation during battery charging and discharging, and also open a new opportunity to modulate the properties of twisted 2D systems with guest species doping in the Moiré structures.

 

Electrochemical reduction of nitric oxide (NOER) is a promising technology for the removal of harmful N-containing species in groundwater under mild conditions. In this work, by means of density functional theory computations, we systematically investigated the potential of utilizing experimentally feasible transition metal–N 4 /graphenes as NOER catalysts. Our results revealed that NO molecules can be moderately activated on a Co–N 4 moiety embedded into graphene, and the subsequent NOER steps can proceed to form either NH 3 at low coverages or N 2 O at higher coverages. Especially, the computed onset potential of NOER on Co–N 4 /graphene ( ca. −0.12 V) is comparable to (or even better than) those on well-established Pt-based catalysts. Thus, Co–N 4 /graphene is a promising single-atom-catalyst with high efficiency for NO electrochemical reduction, which opens a new avenue for NO reduction for environmental remediation. 

The oxygen stacking of O3‐type layered sodium transition metal oxides (O3‐NaTMO₂) changes dynamically upon topotactic Na extraction and reinsertion. While the phase transition from octahedral to prismatic Na coordination that occurs at intermediate desodiation by transition metal slab gliding is well understood, the structural evolution at high desodiation, crucial to achieve high reversible capacity, remains mostly uncharted. In this work, the phase transitions of O3‐type layered NaTMO₂at high voltage are investigated by combining experimental and computational approaches. An OP2‐type phase that consists of alternating octahedral and prismatic Na layers is directly observed by in situ X‐ray diffraction and high‐resolution scanning transmission electron microscopy. The origin of this peculiar phase is explained by atomic interactions involving Jahn–Teller active Fe⁴⁺and distortion tolerant Ti⁴⁺that stabilize the local Na environment. The path‐dependent desodiation and resodiation pathways are also rationalized in this material through the different kinetics of the prismatic and octahedral layers, presenting a comprehensive picture about the structural stability of the layered materials upon Na intercalation.