Kelvin Probe Force Microscopy Reveals Spatially Resolved Charge‐Transfer Mechanism in CdS/BiOBr S‐scheme Heterojunction Photocatalyst

) of n-type semiconductors increases, but a built-in electric field (IEF) persists within the heterojunction. Electrons accumulate on the surface of the reduction semiconductor (RS), resulting in a surface photovoltage (SPV) lower than that of the individual semiconductor, while holes accumulate on the oxidation semiconductor (OS) surface, producing an SPV higher than that of the bare material. The S-scheme heterojunction leads to a remarkable increase in charge separation, with 11 additional photogenerated electrons and 3722 additional holes compared to the bare CdS and BiOBr. These results offer critical insights into the spatially resolved charge-transfer mechanisms of S-scheme heterojunctions.