Synthesis of metal sulfide sensitized zinc oxide-based core/shell/shell nanorods and their photoelectrochemical properties

This paper demonstrates a versatile, facile and low-cost precipitate transformation method to synthesize ZnO/ZnS/MxS (metal sulfide) core/shell/shell (CSS) nanorods (NRs), including ZnO/ZnS/Ag2S, ZnO/ZnS/CuS, ZnO/ZnS/Cu2S, ZnO/ZnS/CdS and ZnO/ZnS/Bi2S3. The sufficient differences between the solubility product constants of ZnO, ZnS and MxS allow ZnO NRs to be converted to ZnO/ZnS and ZnO/ZnS/MxS nanostructures via an intermediary conversion route based on the ion-by-ion growth mechanism. The photocurrent density and efficiency for hydrogen generation of the ZnO/ZnS/Ag2S CSS nanostructure are measured to be up to 15.28 mA cm−2 and 15.92%, respectively, which is, to the best of our knowledge, the highest value ever reported for ZnO-based nanostructures. It is believed that these enhanced performances are attributed to the improved absorption efficiency and desirable gradient energy gap structure. In comparison with some other similar CSS NRs (i.e. ZnO/ZnS/CuS, ZnO/ZnS/Cu2S, ZnO/ZnS/CdS and ZnO/ZnS/Bi2S3) that are successfully prepared through the same method, ZnO/ZnS/Ag2S CSS NR is found to provide the best photoelectrochemical performance.