Segment-Resolved Intramolecular Dual Z-Scheme-Like Electron Transfer Driven by Built-in Electric Field in a Monomeric Photocatalyst for Efficient Photocatalytic H2O2 Production

Abstract Research on built-in electric fields (BIEFs) is typically focused on the interfaces of heterojunctions or the overall behavior of polymeric materials, which often neglects the local electronic interactions within the subcomponents. Here, we propose that a single–component photocatalyst can be regarded as a generalized heterojunction by dividing it into multiple spatially independent segments with different electronic properties. We prepared a conjugated polymer (CN-K/SC) with significant intramolecular charge inhomogeneity by functionalizing sulfonyl cyanide (SC) groups onto carbon nitride (CN) using the facile KSCN molten salt method. This inhomogeneity generates a strong BIEF that drives directional migration of photogenerated carriers. Kelvin probe force microscopy (KPFM), In situ X-ray photoelectron spectroscopy (In situ XPS), and theoretical calculations collectively reveal the complex dynamics of photogenerated carriers. CN-K/SC was divided into three spatially adjacent regions with comparable excitation energies through excited-state calculations and spatial charge distribution analysis. Under the BIEF, these regions interact synergistically to establish a dual Z-scheme-like electron transfer pathway. This pathway enhances charge separation efficiency and boosts the photocatalytic H2O2 production (PHP) rate (approximately 28 times that of the pristine CN). This work establishes a universal segment-based framework that treats monomeric photocatalysts as generalized heterojunctions, providing insights for a thorough examination of their unique intramolecular carrier dynamics.