For highly efficient photoelectrodes, the materials used must have both a broad absorption range and large separation efficiency of photogenerated electron-hole pairs. Type II heterostructures with a ternary shell meet these two requirements and thus are recognized as being an ideal materials system for application in photocatalytic hydrogen production. Here, a ZnO/ZnxCd1-xTe core/shell nanowires array with a broad absorption edge from UV (380 nm) to NIR (855 nm) was fabricated via a chemical vapor-deposition method. More importantly, the ZnO/ZnxCd1-xTe core/shell nanowires array are highly single crystalline, and the composition can be continuously tuned by optimizing the deposition temperature, making the design of the desired photocatalyst possible. As expected, the single-crystalline ternary ZnxCd1-xTe shell greatly enhances the charge separation efficiency and prolongs the lifetime of photogenerated charge carriers, which contribute to the high photocatalytic and photoelectrocatalytic activity under light irradiation. In addition, ZnO/ZnxCd1-xTe core/shell structure show remarkable photocatalytic H2-production activity and high H2-production capability because of the synergistic light absorption of the ternary ZnxCd1-xTe shell and the formation of a type II heterostructure at the interface between the ZnO core and ZnxCd1-xTe shell. This work provides a new material platform for the design of highly efficient solar-fuel devices that demonstrate a broad and controllable absorption from the UV to NIR wavelengths.