Covalently Linked Heterostructures of Phosphorene with MoS₂/MoSe₂ and Their Remarkable Hydrogen Evolution Reaction...

Hydrogen production by photochemical and electrochemical means is an important area of research related to renewable energy. 2D nanomaterials such as C₃N₄ and MoS₂ have proven to be active for the hydrogen evolution reaction (HER). Phosphorene, a mono-elemental 2D layer of phosphorus, is known to catalyze the HER, but the activity is marginal. The use of phosphorene is also limited by its ambient instability. We have been able to prepare covalently cross-linked nanocomposites of phosphorene with MoS₂ as well as MoSe₂. The phosphorene-MoS₂ nanocomposite shows excellent photochemical HER activity yielding 26.8 mmol h^-1 g^-1 of H₂, while only a negligible amount is produced by the physical mixture of phosphorene and MoS₂. The phosphorene-MoS₂ composite also displays high electrochemical HER activity with an onset overpotential of 110 mV, close to that of Pt. The enhanced HER activity of the phosphorene-MoS₂ nanocomposite can be attributed to the ordered cross-linking of the 2D sheets, increasing the interfacial area as well as the charge-transfer interaction between phosphorene and MoS₂ layers. The phosphorene-MoSe₂ nanocomposite also exhibits good photochemical HER activity.