Cobalt sulfide materials have attracted enormous interest as low‐cost alternatives to noble‐metal catalysts capable of catalyzing both oxygen reduction and oxygen evolution reactions. Although recent advances have been achieved in the development of various cobalt sulfide composites to expedite their oxygen reduction reaction properties, to improve their poor oxygen evolution reaction (OER) activity is still challenging, which significantly limits their utilization. Here, the synthesis of Fe3O4‐decorated Co9S8 nanoparticles in situ grown on a reduced graphene oxide surface (Fe3O4@Co9S8/rGO) and the use of it as a remarkably active and stable OER catalyst are first reported. Loading of Fe3O4 on cobalt sulfide induces the formation of pure phase Co9S8 and highly improves the catalytic activity for OER. The composite exhibits superior OER performance with a small overpotential of 0.34 V at the current density of 10 mA cm−2 and high stability. It is believed that the electron transfer trend from Fe species to Co9S8 promotes the breaking of the Co–O bond in the stable configuration (Co–O–O superoxo group), attributing to the excellent catalytic activity. This development offers a new and effective cobalt sulfide‐based oxygen evolution electrocatalysts to replace the expensive commercial catalysts such as RuO2 or IrO2.

Owing to their unique optical, electronic, and catalytic properties, metal nitrides nanostructures are widely used in optoelectronics, clean energy, and catalysis fields. Despite great progress has been achieved, synthesis of defect-rich (DR) bimetallic nitride nanocrystals or related nanohybrids remains a challenge, and their electrocatalytic application for oxygen evolution reaction (OER) has not been fully studied. Herein, the DR-Ni 3 FeN nanocrystals and N-doped graphene (N-G) nanohybrids (DR-Ni 3 FeN/N-G) are fabricated through temperature-programmed annealing and nitridation treatment of NiFe-layered double hydroxides/graphene oxide precursors by controlling annealing atmosphere. In the nanohybrids, the DR-Ni 3 FeN nanocrystals are anchored on N-G, and mainly show twin crystal defects besides ≈10% of stacking faults. Such nanohybrids can efficiently catalyze OER in alkaline media with a small overpotential (0.25 V) to attain the current density of 10 mA cm −2 and a high turnover frequency (0.46 s −1 ), superior to their counterparts (the nearly defect-free Ni 3 FeN/N-G), commercial IrO 2 , and the-state-of-art reported OER catalysts. Except for the superior activity, they show better durability than their counterparts yet. As revealed by microstructural, spectroscopic, and electrochemical analyses, the enhanced OER performance of DR-Ni 3 FeN/N-G nanohybrids originates from the abundant twin crystal defects in Ni 3 FeN active phase and the strong interplay between

Semiconductor heterostructures of two-dimensional (2D) transition metal disulfide (TMD) have opened up approaches toward the integration of each function and implementations in novel energy and electronic devices. However, engineering TMD-based homostructures with tailored properties is still challenging. Herein, we demonstrate a solution-processed growth of vertically aligned 1T-MoS using liquid-phase exfoliated 2H-MoS as self-templates. The unique MoS-based homostructures not only provide more exposed active sites in the edge and basal plane for the electrocatalytic hydrogen evolution reaction (HER) but also improve the mass transfer due to the introduction of high packing porosity. The resultant all-MoS electrocatalysts with an integration of polymorphous MoS nanostructures exhibit a superior HER activity with a low potential of 203 mV at 10 mA cm, a small Tafel slope of 60 mV dec, and a remarkable cyclic stability. This work thus provides a simple and efficient route for the creation of unprecedented MoS-based homostructured materials with exciting properties, especially as an inexpensive alternative to platinum catalysts in electrochemical hydrogen evolution production.

There have been several recent conflicting reports on the ferromagnetism of clean monolayer VSe2. Herein, the controllable formation of 1D defect line patterns in vanadium diselenide (VSe2) monolayers initiated by thermal annealing is presented. Using scanning tunneling microscopy and q‐plus atomic force microscopy techniques, the 1D line features are determined to be 8‐member‐ring arrays, formed via a Se deficient reconstruction process. The reconstructed VSe2 monolayer with Se‐deficient line defects displays room‐temperature ferromagnetism under X‐ray magnetic circular dichroism and magnetic force microscopy, consistent with the density functional theory calculations. This study possibly resolves the controversy on whether ferromagnetism is intrinsic in monolayer VSe2, and highlights the importance of controlling and understanding the atomic structures of surface defects in 2D crystals, which could play key roles in the material properties and hence potential device applications.