Activating ZnO nanorod photoanodes in visible light by Cu ion implantation

Utilization of visible light is of crucial importance for exploiting efficient semiconductor catalysts for solar water splitting. In this study, an advanced ion implantation method was utilized to dope Cu ions into ZnO nanorod arrays for photoelectrochemical water splitting in visible light. X-ray diffraction (XRD) and X-ray photo-electron spectroscopy (XPS) results revealed that Cu⁺ together with a small amount of Cu²⁺ were highly dispersed within the ZnO nanorod arrays. The Cu ion doped ZnO nanorod arrays displayed extended optical absorption and enhanced photoelectrochemical performance under visible light illumination (λ > 420 nm). A considerable photocurrent density of 18 μA/cm² at 0.8 V (vs. a saturated calomel electrode) was achieved, which was about 11 times higher than that of undoped ZnO nanorod arrays. This study proposes that ion implantation could be an effective approach for developing novel visible-light-driven photocatalytic materials for water splitting.