PtNix hollow nanoparticles (HNPs) as a cocatalyst was synthesized by a galvanic replacement method at room temperature, and then was loaded on CdS. The hollow structure of PtNix alloy was confirmed by TEM and STEM. Photocatalytic hydrogen production reaction was performed for PtNix/CdS catalyst under 300 W Xe lamp (lambda >= 420 nm). It is noteworthy that PtNi0.5/CdS shows the highest hydrogen evolution activity of 2.9 mmol/h with QE = 51.24% at 420 nm, which is higher than that of situ-photodeposited Pt onto CdS (0.57 mmol/h). The enhancement of hydrogen evolution performance of PtNi0.5/CdS could be attributed to the porous shell and hollow structure of PtNi0.5 NPs, as well as the strong electronic coupling effect between Pt and Ni. Besides, the sheet structure of CdS in some degree promoted the hydrogen production rate. Therefore, the PtNix HNPs could be a promising cocatalyst of CdS for solar driven hydrogen evolution. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.