Accelerated Interfacial Charge Transfer via Ni 3d-S 3p Orbital Hybridization in a CdS/NiPc S-Scheme Heterojunction for Highly-Selective H₂O₂ Photosynthesis.

The rapid recombination of photogenerated charge carriers severely restricts the efficiency of photocatalytic H₂O₂ production. While S-scheme heterojunctions can prominently promote charge separation and transfer, the atomic-level mechanism of interfacial charge transfer remains inadequately understood. Herein, a prototype cadmium sulfide/nickel phthalocyanine (CdS/NiPc) S-scheme heterojunction photocatalyst with interfacial Ni─S bonds was fabricated via a facile one-step hydrothermal method. The Ni─S bond serves as an atomic-scale charge transfer channel through Ni 3d-S 3p orbital hybridization, significantly accelerating oriented charge migration across the interface. Consequently, the optimized CdS/NiPc-10% achieves a remarkable H₂O₂ production rate of 34.4 mmol·L⁻¹·g⁻¹·h⁻¹, along with excellent cycling stability. Combined X-ray absorption fine structure (XAFS), in situ irradiated X-ray photoelectron spectroscopy (ISIXPS), and femtosecond transient absorption spectroscopy (fs-TAS) analysis confirm the existence of Ni─S bond and dominant S-scheme charge transport pathway. Moreover, density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) spectra reveal that the Ni 3d-S 3p orbital hybridization adjusts the O₂ adsorption configuration from Yeager-type to Pauling-type, suppressing O─O bond cleavage and stabilizing the *OOH intermediate, thereby promoting the two-electron oxygen reduction pathway for selective H₂O₂ production. This work elucidates how interfacial chemical bonds regulate charge dynamics via orbital hybridization, offering new insights for designing efficient S-scheme photocatalysts.