title: Trade-off between Zr Passivation and Sn Doping on Hematite Nanorod Photoanodes for Efficient Solar Water Oxidation: Effects of a ZrO2 Underlayer and FTO Deformation.
abstract: Herein we report the influence of a ZrO2 underlayer on the PEC (photoelectrochemical) behavior of hematite nanorod photoanodes for efficient solar water splitting. Particular attention was given to the cathodic shift in onset potential and photocurrent enhancement. Akaganite (β-FeOOH) nanorods were grown on ZrO2-coated FTO (fluorine-doped tin oxide) substrates. Sintering at 800 °C transformed akaganite to the hematite (α-Fe2O3) phase and induced Sn diffusion into the crystal structure of hematite nanorods from the FTO substrates and surface migration, shallow doping of Zr atoms from the ZrO2 underlayer. The ZrO2 underlayer-treated photoanode showed better water oxidation performance compared to the pristine (α-Fe2O3) photoanode. A cathodic shift in the onset potential and photocurrent enhancement was achieved by surface passivation and shallow doping of Zr from the ZrO2 underlayer, along with Sn doping from the FTO substrate to the crystal lattice of hematite nanorods. The Zr based hematite nanorod photoanode achieved 1 mA/cm(2) at 1.23 VRHE with a low turn-on voltage of 0.80 VRHE. Sn doping and Zr passivation, as well as shallow doping, were confirmed by XPS, Iph, and M-S plot analyses. Electrochemical impedance spectroscopy revealed that the presence of a ZrO2 underlayer decreased the deformation of FTO substrate, improved electron transfer at the hematite/FTO interface and increased charge-transfer resistance at the electrolyte/hematite interface. This is the first systematic investigation of the effects of Zr passivation, shallow doping, and Sn doping on hematite nanorod photoanodes through application of a ZrO2 underlayer on the FTO substrate.
authors.affiliation: Division of Biotechnology, Safety, Environment and Life Science Institute, College of Environmental and Bioresource Sciences, Chonbuk National University , Iksan 570-752, Republic of Korea.
authors.forename: Arunprabaharan
authors.initials: A
authors.lastname: Subramanian
authors.affiliation: Division of Biotechnology, Safety, Environment and Life Science Institute, College of Environmental and Bioresource Sciences, Chonbuk National University , Iksan 570-752, Republic of Korea.
authors.forename: Alagappan
authors.initials: A
authors.lastname: Annamalai
authors.affiliation: Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Republic of Korea.
authors.forename: Hyun Hwi
authors.initials: HH
authors.lastname: Lee
authors.affiliation: Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Republic of Korea.
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Choi
authors.affiliation: Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM) , Daejeon 305-350, Korea.
authors.forename: Jungho
authors.initials: J
authors.lastname: Ryu
authors.affiliation: Division of Biotechnology, Safety, Environment and Life Science Institute, College of Environmental and Bioresource Sciences, Chonbuk National University , Iksan 570-752, Republic of Korea.
authors.forename: Jung Hee
authors.initials: JH
authors.lastname: Park
authors.affiliation: Division of Biotechnology, Safety, Environment and Life Science Institute, College of Environmental and Bioresource Sciences, Chonbuk National University , Iksan 570-752, Republic of Korea.
authors.forename: Jum Suk
authors.initials: JS
authors.lastname: Jang
keywords: akaganite; cathodic shift; onset potential; passivation; photoelectrochemical cells; shallow doping