Photoelectrochemical Imaging of Charge Separation between MoS₂ Triangles and Insulating SiO₂ Support

The role of the insulating support in photocatalysis is poorly understood. Using high-resolution photo-scanning electrochemical microscopy (photo-SECM), we observed significant spatial charge separation in few-layer-thick molybdenum disulfide (MoS₂) triangles attached to a SiO₂ substrate. Spatially resolved surface photovoltage (SPV) measurements revealed that photogenerated holes migrate from MoS₂ to the SiO₂ surface and travel laterally over distances exceeding 2 μm, driven by the built-in electric field of ∼1.7 kV/cm. In thicker and less uniform flakes, the charge separation is dominated by internal driving forces within MoS₂, without significant contribution from SiO₂. These findings underscore the importance of insulator-semiconductor interactions for effective charge separation, suggesting a new strategy for optimizing photocatalytic systems.