Insight into the impact of surface hydrothermal carbon layer on photocatalytic performance of ZnO nanowire

Due to the thorough interfacial contact and ignorable impediment for absorbing the incident light, the uniform hydrothermal carbon (HTC) coating is confirmed to efficiently enhance the photocatalytic performance of photocatalysts. To further explore the detailed effect of the HTC layer with various physical and chemical properties, a series of 1D ZnO@C nanocables are prepared via uniformly depositing HTC and high-temperature calcinating. The HTC layer thickness could be precisely tuned in a range of 3-8.5 nm by controlling the carbon source amount, while the calcination will decline the surface coating density of HTC and significantly increase its electroconductivity. The adsorption capacity of various ZnO@C nanocables is systematacially investigated for methylene blue (MB), as well as their photocatalytic performance for the MB-degradation. It is found that the surface adsorbability of ZnO@C nanocables generally increases with the HTC thickness, whereas 5 nm will maximally improve the photocatalytic activity of ZnO. Furthermore, the ZnO@C product calcinated at 600 degrees C simultaneously possesses the good surface adsorbability and high electron-transfer efficiency, thus showing the superior photocatalytic performance. Finally, a rational mechanism has been proposed to explain the improved effect of the coated HTC layer on the photocatalytic performance of primary ZnO nanowires.