A ternary heterostructure of CdS/Au/ZnO, where a core–shell structure of Au/CdS is selectively deposited on the polar surface of ZnO induced by the surface polar charges of ZnO crystals, is prepared through a two-step self-assembly process. The resultant heterostructure shows an activity 4.5 times higher in photocatalytic hydrogen evolution from water containing Na₂S/Na₂SO₃ electron donors than the binary CdS/ZnO heterostructure as a result of the effective vectorial Z-scheme transfer of photogenerated charge carriers between ZnO and CdS mediated by Au nanoparticles at the interface.