In the past decade, photocatalytic H 2 production over CdS semiconductor has garnered considerable interest due to its visible-light response, suitable band structure, and controllable morphologies. To pursue higher photocatalytic efficiency and more feasibility for practical industrial applications, Cd(OH) 2 nanoparticle decorated CdS rod composites were designed and successfully fabricated in this study by a facile one-step hydrothermal method in strong alkali NaOH solution. The synthesis process followed a “mother liquor circulation” criteria since no NaOH was lost during the whole preparation course, which could greatly save costs and be conducive to the realization of large-scale production. When the content of Cd(OH) 2 was 17.6 mol% in the obtained composite, the photocatalytic H 2 production rate reached the highest (579.0 μmol h −1 ) with the help of 0.6 wt% platinum (Pt), which was more than 386 and 15 times higher than that of Pt/Cd(OH) 2 and Pt/CdS, respectively. It was evidenced that such surprising and prominent enhancement of photoactivity was mainly attributed to the presence of Cd 0 as an electron transport intermediary, which was produced by in-situ photoreduction of Cd(OH) 2 interfacial layer between CdS and Pt. This work could not only highlight the significant roles of Cd(OH) 2 on invigorating the photoactivity of CdS for H 2 production, but also open an avenue of using the concept of mother liquor circulation in the photocatalyst synthesis process to satisfy the industrial manufacture requirement.