Fig. 1. (a) Conceptual representation of the preparation process for the catalytic materials. Morphological characterization via scanning electron microscopy for pristine CN (b), N-doped CN (NCN) (c), and the CN/NCN composite (d). Corresponding transmission electron microscopy analysis of CNUN (e), CNND (f), and the integrated CNND/CNUN structure (g). Adapted with permission from Ref. [9]. Copyright 2025, Wiley-VCH.

Fig. 2. (a) Spatial arrangement of atomic charges within the CNND/CNUN interface (Purple: N, Brown: C, White: H, Red: O). (b) Depth-dependent profile of the electrostatic potential across the CNND/CNUN system. (c) Planar charge density difference map (xy-plane), where yellow regions indicate electron depletion and blue zones signify electron accumulation. (d) Proposed photocatalytic reaction pathway occurring on the CNND/CNUN homojunction. Adapted with permission from Ref. [9]. Copyright 2025, Wiley-VCH.