Application of chemical vapor–deposited monolayer ReSe2 in the electrocatalytic hydrogen evolution reaction

Controlled synthesis of structurally anisotropic rhenium diselenide (ReSe 2 ) with macroscopically uniform and strictly monolayer thickness as well as tunable domain shape/size is of great interest for electronics-, optoelectronics-, and electrocatalysis-related applications. Herein, we describe the controlled synthesis of uniform monolayer ReSe 2 flakes with variable morphology (sunflower- or truncated-triangle-shaped) on SiO 2 /Si substrates using different ambient-pressure chemical vapor deposition (CVD) setups. The prepared polycrystalline ReSe 2 flakes were transferred intact onto Au foil electrodes and tested for activity in the hydrogen evolution reaction (HER). Interestingly, compared to the compact truncated-triangle-shaped ReSe 2 flakes, their edge-abundant sunflower-shaped counterparts exhibited superior electrocatalytic HER activity, featuring a relatively low Tafel slope of ∼76 mV/dec and an exchange current density of 10.5 μA/cm 2 . Thus, our work demonstrates that CVD-grown ReSe 2 is a promising two-dimensional anisotropic material for applications in the electrocatalytic HER.