Abstract: ZnO nanorods (NRs) were grown onto ZnO seed layer deposited FTO glass substrate via hydrothermal technique at ~95 °C. The as-deposited samples were further heat-treated at ~400 °C in a furnace under air at-mosphere. With varying time, the kinetic study of the growth of ZnO towards NRs formation was also performed. To enhance oxygen defects such as oxygen vacancy in the NRs, the thermally cured samples were further heat-treated in 5% H2 gas atmosphere at ~350 °C. Morphological and microstructural analyses, estimation of oxygen vacancy in the samples were carried out by field emission scanning and transmission electron mi-croscopies and X-ray photoelectron spectroscopy, respectively. Moreover, the optical properties of the specimen were also characterized by photoluminescence spectral study. A co-relation was also made between the reduced gas treatment time and the photoelectrochemical (PEC) activity of the samples. The ZnO NRs synthesized by optimizing the time for the growth of NRs and the reduced gas treatment time exhibited sig-nificant improvement in PEC activity. This work could make an avenue for enhancing the PEC activity of other hierarchically structured metal oxide semiconductors.

Key words: hydrothermal growth technique, ZnO nanorods, morphology and microstructure, oxygen defects, photoe-lectrochemical activity