Transition-metal nitride or carbide nanosheets can have useful chemical and physical properties, e.g., for broadband light absorption and photothermal conversion—i.e., turning sunlight into heat. Mo₅N₆ nanosheets are a candidate for such applications, but developing efficient syntheses to produce these nitrides is still a challenge.

Dan Liu, Joselito Razal, Weiwei Lei, Deakin University, Geelong, Australia, and colleagues have developed an approach for the production of molybdenum nitride nanosheets at the gram scale using amine-functionalized MoS₂ as a precursor. The team first used ball-milling to functionalize the MoS₂ using urea. The functionalized nanosheets and urea as a nitrogen source were then placed in a horizontal furnace under an Ar atmosphere and heated. The urea is decomposed to form NH₃, which travels along the furnace to the amine-functionalized MoS₂ nanosheets and reacts to form H₂S and the desired molybdenum nitride nanosheets. The activation of the precursor by amine functionalization significantly reduces the reaction time, from several hours to as little as 15 min.

The prepared molybdenum nitride nanosheets are chemically stable. The nanosheets were used to fabricate photothermal devices, using a melamine foam support, and showed excellent light-to-heat conversion. The synthetic approach can also be extended to other nitrides such as W₂N₃, Ta₃N₅, or Nb₄N_5.

• 2D Higher‐Metal Nitride Nanosheets for Solar Steam Generation,
  Lifeng Wang, Jing Shang, Guoliang Yang, Yuxi Ma, Liangzhi Kou, Dan Liu, Huaying Yin, Dylan Hegh, Joselito Razal, Weiwei Lei,
  Small 2022.
  https://doi.org/10.1002/smll.202201770