Engineering Low-Crystallinity-Induced Localized Dipole Fields in Cd _0.5 Zn _0.5 S for Synergistic Enhancement of Photocatalytic H ₂ O ₂ Generation

The direct photocatalytic production of H₂O₂ from water and air offers a sustainable route to decarbonize the energy-intensive anthraquinone process. However, its efficiency remains limited by sluggish exciton dissociation and rapid charge carrier recombination, typically requiring sacrificial agents that compromise the process economics. Herein, we design Cd_0.5Zn_0.5S nanoparticles with symmetry-broken atomic arrangements by modulating crystallinity, an intrinsic material property. This modulation generates numerous localized dipole fields. These fields actively promote exciton dissociation and direct charge carrier migration, boosting charge utilization. As a result, the optimized catalyst achieved an H₂O₂ yield of 1.36 mmol g^-1 h^-1 using only dissolved O₂ as the electron acceptor and without additional sacrificial agents. The role of the dipole fields in promoting exciton dissociation and charge separation has been unequivocally demonstrated through Kelvin probe force microscopy, time-resolved photoluminescence, and femtosecond transient absorption spectroscopy. This work establishes crystallinity-mediated dipole engineering as an effective strategy for carrier management in photocatalytic systems beyond conventional crystalline materials.