Polarization-Tunable Photoelectrochemistry at Individual Anisotropic ReS₂ and Its Homostructure Interfaces

Light polarization offers a powerful yet underexplored handle to control photoelectrochemical processes in two-dimensional (2D) semiconductors. Here, we demonstrate polarization-tunable photoelectrochemistry at anisotropic 2D ReS₂ interfaces, providing a new strategy to manipulate light-driven charge dynamics. Using scanning electrochemical cell microscopy (SECCM) under controlled photoexcitation, we systematically probe how incident wavelength, layer thickness, and van der Waals stacking govern polarization sensitivity at the nanoscale. The dichroic ratio increases by ∼50% as the excitation wavelength approaches the band edge and decreases systematically with thickness, while the polarization phase shift grows with both wavelength and layer number due to ReS₂ birefringence. By stacking ReS₂ layers with controlled twist angles and thickness contrasts, we achieve programmable junction behavior ranging from nearly isotropic responses in 90°-twisted bilayers to layer-dominant anisotropy dictated by photogeneration balance. For arbitrary twist angles, the phase shifts of the individual layers add coherently, enabling predictive control of the angular response. This work establishes light polarization as a precise and versatile control knob for nanoscale photoelectrochemistry, offering a new paradigm for designing optoelectronic and photocatalytic devices with intrinsic polarization selectivity.