<p>The selective activation of X–H (X=C, O) bonds in benzyl alcohol oxidation coupled with hydrogen evolution enables the co-production of clean H₂ fuel and high-value organic compounds. However, the efficiency of this combined reaction is still limited by inefficient charge separation and insufficient activation of the X–H bonds. Herein, a PT/ZnIn₂S₄-V_Zn (PT/ZIS-V_Zn) catalyst was developed using a defect-engineered S-scheme heterojunction strategy, which exhibits a pronounced bulk-interfacial cascade polarization effect. This structure significantly enhances the separation and migration efficiency of photogenerated charge carriers, thereby improving hole supply for α-C–H activation. Moreover, Zn vacancies effectively promote the adsorption and activation of OH⁻ ions derived from water dissociation, thus enhancing the nucleophilic oxidation efficiency of the adsorbed *OH toward the O–H bond in the ·CH(OH)Ph intermediate. Owing to the dual enhancement of charge separation and X–H bond activation, the PT/ZIS-V_Zn S-scheme heterojunction achieved highly efficient photocatalytic activities of 17.70 and 16.52 mmol g⁻¹ h⁻¹ for H₂ and benzaldehyde production, respectively, representing 2.7- and 2.8-fold enhancements compared to pristine ZnIn₂S₄. This study elucidates the mechanism of enhanced X–H bond activation and provides practical guidance for designing efficient photocatalysts for alcohol oxidation-coupled H₂ evolution.</p>