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.