title: Nanostructure-Preserved Hematite Thin Film for Efficient Solar Water Splitting.
abstract: High-temperature annealing above 700 °C improves the activity of photoelectrochemical water oxidation by hematite photoanodes by increasing its crystallinity. Yet, it brings severe agglomeration of nanostructured hematite thin films and deteriorates electrical conductivity of the transparent conducting oxide (TCO) substrate. We report here that the nanostructure of the hematite and the conductivity of TCO could be preserved, while the high crystallinity is attained, by hybrid microwave annealing (HMA) utilizing a graphite susceptor for efficient microwave absorption. Thus, the hematite thin-film photoanodes treated by HMA record 2 times higher water oxidation photocurrents compared to a conventional thermal-annealed photoanode. The enhanced performance can be attributed to the synergistic effect of a smaller feature size of nanostructure-preserved hematite and a good electrical conductivity of TCO. The method could be generally applied to the fabrication of efficient photoelectrodes with small feature sizes and high crystallinity, which have been mutually conflicting requirements with conventional thermal annealing processes.
authors.affiliation: †Division of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, Republic of Korea.
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: †Division of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, Republic of Korea.
authors.forename: Duck Hyun
authors.initials: DH
authors.lastname: Youn
authors.affiliation: ‡Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang 790-784, Republic of Korea.
authors.forename: Ju Hun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: §Busan Center, Korea Basic Science Institute, Busan 609-735, Korea.
authors.forename: Hyun Gyu
authors.initials: HG
authors.lastname: Kim
authors.affiliation: †Division of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, Republic of Korea.
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Lee
keywords: crystallinity; hematite; hybrid microwave annealing; nanostructures; solar water splitting