Polarization Dependent Photoelectrochemistry of Anisotropic Rhenium Disulfide

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have garnered significant attention as promising photocatalysts due to their high surface area and tunability. Rhenium disulfide (ReS2) is a distinctive member of the TMD family, notable for its unique in-plane anisotropy resulting from diamond-shaped rhenium chains along the crystal's b-axis. In this study, we examined the effects of linearly polarized light on the photoelectrochemical response of layered ReS2. The crystals were mechanically exfoliated and placed onto a conductive indium tin oxide-coated substrate. The b-axis orientation was identified by the longer crystal edge observed in the optical micrographs of individual ReS2 flakes. Atomic force microscopy (AFM) was used to determine the thickness of the flakes. The photoelectrochemical response was probed directly using scanning electrochemical cell microscopy (SECCM). Under linearly polarized light excitation, the photocurrent associated with the iodide/triiodide redox reaction at ReS2 showed a strong dependence on the polarization angle. Specifically, maximum photocurrent was obtained when the electric field orientation was along the b-axis, while lowest current was observed with the electric field orientation perpendicular to the b-axis. Additionally, the sensitivity of the photo response to polarization diminished as the thickness increased from 15 nm to 90 nm. These insights provide a direct correlation between structural orientation and performance of anisotropic photocatalysts.