Effect of exposure time on the growth of self-supporting ZnO nanowire arrays and their photocatalytic behavior

•Self-supporting ZnO NWAs were successfully fabricated by hydrothermal process.•We studied the effect of the exposure time on the structure of NWAs.•The photocatalytic activity and durability were studied.•Finally, an optimized growth condition was proposed.

We have successfully fabricated self-supporting ZnO nanowire arrays (NWAs) by recently proposed versatile hydrothermal process. The effect of exposure time on microstructure and photocatalytic performance of ZnO NWAs has been analyzed for the first time, which is the main finding of the present work. Specifically, with increasing exposure time, the vertical alignment is improved and the diameter of NWAs is decreased. Under 15 min exposure time, the obtained ZnO NWAs exhibit the most uniform, dense, and thin arrays. SEM images show that all the NWAs are about 200–300 nm in diameter and 9 μm in length. Furthermore, photocatalytic tests indicated that the as-prepared ZnO NWAs exposed with 15 min exhibited the best activity for photo-degradation of organic dye under UV light irradiation. After 5 recycles, the sample did not exhibit an obvious loss in activity, confirming its good activity upon recycling.