Synthesis of 2‐Inch Hexanary Medium‐Entropy Alloy Monolayer Via Chemical Vapor Deposition with Superior Photoelectric Properties

Abstract Mixing entropy engineering is a promising strategy to tune the physical and chemical properties of materials. Although high‐entropy in van der Waals bulk solids have been reported, entropy engineering in 2D monolayers remains unconquered. In this work, the epitaxial growth of a 2‐inch 1T″ hexanary medium‐entropy alloy monolayer (Re a W b Mo c In d S x Se y ) is reported via the chemical vapor deposition method. The atomic structure and chemical composition are confirmed by X‐ray photoelectron spectroscopy, scanning transmission electron microscopy, energy dispersive X‐ray spectroscopy and electron energy loss spectroscopy, illustrating the uniform distribution of the six elements. The hexanary medium‐entropy alloy photodetectors show an ultrawide photo‐response from visible to near‐infrared wavelengths with a responsivity of 100.2 A W −1 under 520 nm laser illumination. Meanwhile, the hexanary medium‐entropy alloy monolayer exhibits excellent electrocatalytic hydrogen production with an overpotential of 176.6 mV in dark. Importantly, an overpotential of 43.7 mV at 10 mA cm −2 with a lowered Tafel slope of 51.9 mV dec −1 under 520 nm laser irradiation is obtained due to the excellent conductivity. The work opens a new way to design mixing = entropy alloys and enables the application of transition metal dichalcogenides in photo‐enhanced electrocatalytic hydrogen production.