Improved visible-light photocurrent based on ZnO/ZnS core-shell nanorods via interfacial engineering

Abstract

Vertically aligned quasi two-dimensional (2D) ZnO nanorods (NRs) on carbon fiber paper were prepared by a modified hydrothermal approach, an individual ZnO nanorod has a diameter of 100-200 nm and a length of ∼1 μm. ZnO/ZnS core-hell hierarchal structures with an outer ZnS shell of ∼25 nm were fabricated under an elaborate sulfidation treatment. Compared to ZnO NRs a depressed near band emission at 380 nm and a significant enhanced visible light emission around 500 nm were observed for the ZnO/ZnS core-hell NRs from photoluminescence spectra. XPS and ESR measurements were carried out to study the ions constituents and the defects of the prepared samples. The prepared samples were used as photoelectrodes in visible-light self-powered photoelectrochemical cell-type detector. And an enhanced photocurrent of 6.79 μA was obtained, which is ten times as high as that of the bare ZnO electrode. The results show that the existence of sulfur vacancies and the formation of ZnO/ZnS heterostructure were able to promote photocurrent performance, the former increases the carrier concentration and leads to an upshift of work function; the latter makes the band bend and the photogenerated e-p pairs can be separated efficiently. The results will be helpful to implement visible-light device based on heterostructure via interfacial engineering.