Accumulation of Long‐Lived Photogenerated Holes at Copper Yolk‐Shell Heterojunctions via Heterogeneous Contraction and Reduction Strategies for Enhanced Photocatalytic Oxidation

Active holes outperform photoelectron‐mediated oxygen reduction in degrading recalcitrant organics under anaerobic conditions, yet their utilization is limited by rapid charge recombination. This challenge was addressed through Cu‐based yolk‐double‐shell microspheres (Cu/Cu 2 O@C‐2shell) engineered via heterogeneous contraction and reduction strategies. Work function analyses confirm Schottky junction‐driven electron transfer from Cu 2 O to Cu, generating an internal electric field that suppresses backflow. Density functional theory reveals Cu‐mediated enhancement of near‐Fermi states (Cu 3d orbitals) and a directional Cu 2 O → Cu → C electron pathway, spatially isolating holes in Cu 2 O. Finite‐difference time‐domain simulations reveal light‐induced electric field gradients in the dual‐shell architecture: Cu 0 ‐mediated localized surface plasmon resonance effect enhances surface field concentration, while hierarchical interfaces create an outward‐to‐inward gradient, directing electron migration inward and stabilizing oxidative holes at the surface. The optimized (Cu/Cu 2 O)@C‐2shell exhibits 38‐fold higher tetracycline degradation under sunlight versus benchmarks, with treated water supporting Escherichia coli survival and wheat growth. This study provides a design strategy for the accumulation of long‐lived holes on semiconductor photocatalysts.