The Controllable Synthesis of High-Quality Two-Dimensional Iron Sulfide with Specific Phases.

2D Fe-chalcogenides have drawn significant attention due to their unique structural phases and distinct properties in exploring magnetism and superconductivity. However, it remains a significant challenge to synthesize 2D Fe-chalcogenides with specific phases in a controllable manner since Fe-chalcogenides have multiple phases. Herein, a molecular sieve-assisted strategy is reported for synthesizing ultrathin 2D iron sulfide on substrates via the chemical vapor deposition method. Using a molecular sieve and tuning growth temperatures to control the partial pressures of precursor concentrations, hexagonal FeS, tetragonal FeS, and non-stoichiometric Fe7 S8 nanoflakes can be precisely synthesized. The 2D h-FeS, t-FeS, and Fe7 S8 have high conductivities of 5.4 × 105 S m-1 , 5.8 × 105 S m-1 , and 1.9 × 106 S m-1 . 2D tetragonal FeS shows a superconducting transition at 4 K. The spin reorientation at ≈30 K on the non-stoichiometric Fe7 S8 nanoflakes with ferrimagnetism up to room temperature has also been observed. The controllable synthesis of various phases of 2D iron sulfide may provide a route for synthesizing other 2D compounds with various phases.

Interfacial engineering of tungstic disulfide-carbide heterojunction for high-current-density hydrogen evolution.

Developing low-cost and high-efficiency electrocatalysts to electrolyze water is an effective method for large-scale hydrogen production. For large-scale commercial applications, it is crucial to call for more efficient electrocatalysts with high-current density (≥1000 mA cm-2). However, it is challenging to simultaneously promote the large-scale production and hydrogen evolution reaction (HER) activity of these hydrogen catalysts. Herein, we report the large area tungstic disulfide-carbide (W/WS2-WC) heterojunction electrode vertically grown on an industrial-grade tungsten substrate by the solid-state synthesis method. The W/WS2-WC heterojunction electrode achieves a low overpotential of 473 mV at 1000 mA cm-2 in alkaline electrolytes.