Curved‐Slit Effect Induced Nucleation for g‐C ₃ N ₄ Nanorings with Double Concaves and Enhanced Photocatalysis

Abstract The design and exploration of novel nanostructures have emerged as a prominent focus in nanoscience research over recent decades. Nanoring‐shaped materials, with unique topological and functional characteristics, hold immense potential in electrochemistry, electromagnetic absorption, photocatalysis, and biomedicine. However, high‐purity nanoring materials synthesized at a large scale pose significant challenges due to the thermodynamic barriers associated with generating anisotropic curvatures. Herein, a curved‐slit‐induced nucleation strategy is proposed for nearly pure (≈100%) synthesis of graphitic carbon nitride (g‐C 3 N 4 ) nanorings (RCNs) with distinctive double‐concave geometries during selective chemical vapor deposition (CVD). Fluid simulations reveal diverse fluid dynamics, including velocity, static pressure, and vorticity, facilitating the locally targeted deposition of g‐C 3 N 4 within the gaps of adjacent stacked SiO 2 nanospheres. Synergistic interactions between the silicon hydroxyl (Si‐OH) on the SiO 2 surface and g‐C 3 N 4 further direct site‐specific deposition. Temperature‐dependent polymerization yields intermediate with tunable adhesion properties and the optimal formation energy (−1.98 eV) for g‐C 3 N 4 /SiO₂ interface rationalizes the high selectivity of deposition in the contact regions of the nanospheres. The resulting RCNs feature a distinctive double‐concave nanostructure that enhances light‐trapping via multiple reflection pathways and delivers exceptional photocatalytic performance. This work expands the design of nanomaterials with unique nanoring structures and their application in photocatalysis.