Ultra-thin coating of g-C3N4 on an aligned ZnO nanorod film for rapid charge separation and improved photodegradation performance

Abstract

Type II heterogeneous films with one dimensional (1D) zinc oxide (ZnO) nanorods coated with a graphitic carbon nitride (g-C₃N₄) layer (1D ZnO/gC₃N₄) were fabricated by a simple reflux and thermal vapor condensation process. The grown 1D ZnO/gC₃N₄ films were used to degrade methylene blue (MB) dye under visible-light irradiation. Additionally, photoelectrochemical (PEC) measurements were conducted to explore charge separation and transportation processes. The fabricated films had a photocurrent density of 0.12 mA cm⁻², which is 3.7-times higher than that of bare ZnO nanorods, and had good stability over 5 h. Moreover, the photocatalytic activities of ZnO with the g-C₃N₄ films performed well over multiple cycles without requiring a complex washing process for the photocatalytic recovery step. The improved performance stemmed from direct coating of an ultra-thin g-C₃N₄ layer (<10 nm thick) over ZnO nanorods, which induced high optical absorbance in the visible range, effective charge separation and transportation and low interfacial charge transfer resistance. A photodegradation mechanism was proposed based on the generation of OH˙ and hole radicals during MB dye degradation; these radicals were verified using tert-butanol and EDTA-2Na scavengers. The fabricated core–shell films are very promising components for PEC devices for water purification applications.