Abstract
Hydrogen plasma treatment is widely used to modify the surface and electronic properties of zinc oxide, yet its influence on photoelectrochemical performance remains insufficiently understood. In this work, vertically aligned zinc oxide nanorods were synthesized using spin coating and chemical bath deposition, followed by low-power hydrogen plasma treatment to investigate the relationship between structural, optical, electrical, and photoelectrochemical properties. Structural analysis confirmed the preservation of the wurtzite phase and nanorod alignment after plasma exposure. Surface-sensitive spectroscopic studies revealed modification and partial passivation of defect states. Optical measurements showed suppression of defect-related emission together with enhancement of near-band-edge emission. Electrical characterization indicated a significant reduction in sheet resistance and improved charge transport properties. Electrochemical measurements demonstrated enhanced photocurrent density and reduced charge-transfer resistance, indicating improved interfacial charge transfer kinetics. These results show that hydrogen plasma treatment effectively modifies surface defect states, enhances carrier transport, and improves charge separation without compromising structural integrity. The findings highlight hydrogen plasma processing as a promising approach for defect engineering and optimization of zinc oxide photoanodes for photoelectrochemical applications.