In this study β-FeOOH (akaganeite) nanorods (NR) were synthesized based on L. Vayssieres’s famous hydrothermal method. Hydrothermally synthesized β-FeOOH NR can be applied as a solar water splitting (SWS) cell after phase transition to α-Fe2O3 (hematite) by post-annealing process. His hydrothermal method includes 3 materials: hydrochloric acid (HCl), iron chloride hexa-hydrate (FeCl3·6H2O, ICHH), sodium nitrate (NaNO3, SN). The amount (concentration) of the materials was controlled in hydrothermal synthesis of β-FeOOH NR to inspect the effects of each material on their shape and photoelectrochemical (PEC) efficiency after phase transition to hematite. XRD, SEM, TEM, UV-VIS spectroscopy and 3 electrodes experiment for PEC measurement were performed for that reason. According to XRD result, it was verified that their crystalline structure does not depend on the amount of materials. UV-VIS optical spectroscopy results could not explain why the difference of PEC efficiency takes place. The reason was found in the shape of NR, especially the length. The most important result is that HCl, ICHH and SN all make NR’s length be longer and their extended length hampers the PEC performance of NR. It is because of the short charge carrier lifetime and hole diffusion length of α-Fe2O3. The most efficient sample had the shortest average length. By reducing the concentration of ICHH and not using HCl and SN, it was able to shorten the average length of NR to 340nm and get the highest value of photocurrent: 220uA/cm . It is about 14 times greater than that of NR synthesized by L. Vayssieres’ method. Consequently, the PEC efficiency is inversely proportional to NR’s length.
Thesis Advisor: Prof. Junyeob Yeo