The p-n heterojunction with multi-parallel built-in electric fields forms localized "electron sink" for directional non-uniform transfer of photogenerated carriers

Abstract

The internal electric field can induce photogenerated carrier migration. Nevertheless, the spatial arrangement of internal electric fields (independent, series, and parallel) is intricate, which poses a challenge in determining the charge dynamics and process mechanisms. Here, we propose a strategy for in-situ growth of Co1−xS nanosheets and Co3O4 nanowires on the surface of cobalt foam (CoF). Each nanosheet is tightly connected to multiple nanowires to form multiple parallel circuits. Notably, DFT and in-situ characterization demonstrate that Co1−xS, with its low Fermi level, can act as an electron "pump" to spontaneously transfer interface electrons to multiple contacting nanowires, forming a multi-parallel built-in electric field (MPBIEF) and generating localized "electron sink". Remarkably, this unique structure promotes the directional asymmetric dispersion movement of carriers under illumination conditions, effectively reducing the recombination probability. Moreover, TDOS electronic state analysis reveals the interface enhancement mechanism of CoF@CS@CO, and a fixed-bed photocatalytic flow treatment system is developed.