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

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_aW_bMo_cIn_dS_xSe_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.