Selenene/WSe₂ Heterostructures for Efficient Photoelectrocatalytic Hydrogen Evolution

The van der Waals (vdW) heterostructures, achieved by integrating atomically thin materials with distinct band structures and interfaces, exhibit diverse properties, enabling unprecedented opportunities for various device applications. Herein, we demonstrate controllable growth of vertically stacked heterobilayers (hBLs) of atomically thin selenene and WSe2 through a single-step-confined space chemical vapor transport (CVT) strategy. With an aim to leverage the electrocatalytic activity of the WSe2 domain toward hydrogen generation, along with the high photoresponsivity of CVT-grown selenene domains, we fabricate a microreactor device assembly to study the photoenhanced catalytic performance of the heterobilayer single domains toward hydrogen evolution. When exposed to light, the Se/WSe2 hBL exhibits a significant improvement in the hydrogen evolution reaction (HER) activity with a much lower overpotential and a smaller Tafel slope compared to their pristine counterparts. Control experiments carried out on mechanically stacked hBLs show poor HER activity, further confirming the effect of the interface on the overall photoenhanced HER performance of the vertical bilayer structures. The mechanism of the enhanced HER activity of the hBL is explored through electrochemical impedance studies and Ultraviolet photoelectron spectroscopy (UPS) measurements. The enhanced catalytic efficiency is attributed to effective electrical coupling and improved charge transfer in the Se/WSe2 hBLs.