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Effect of tetravalent dopants on hematite nanostructure for enhanced photoelectrochemical water splitting
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics. Division of Biotechnology, Safety, Environment and Life Science Institute, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 54596, Republic of Korea.ORCID iD: 0000-0002-5210-2645
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2018 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 427, p. 1203-1212Article in journal (Refereed) Published
Abstract [en]

In this paper, the influence of tetravalent dopants such as Si4+, Sn4+, Ti4+, and Zr4+ on the hematite (alpha-Fe2O3) nanostructure for enhanced photoelectrochemical (PEC) water splitting are reported. The tetravalent doping was performed on hydrothermally grown akaganeite (beta-FeOOH) nanorods on FTO (fluorine-doped tin-oxide) substrates via a simple dipping method for which the respective metal-precursor solution was used, followed by a high-temperature (800 degrees C) sintering in a box furnace. The photocurrent density for the pristine (hematite) photoanode is similar to 0.81 mA/cm(2) at 1.23 V-RHE, with an onset potential of 0.72 V-RHE; however, the tetravalent dopants on the hematite nanostructures alter the properties of the pristine photoanode. The Si4+-doped hematite photoanode showed a slight photocurrent increment without a changing of the onset potential of the pristine photoanode. The Sn4+- and Ti4+-doped hematite photoanodes, however, showed an anodic shift of the onset potential with the photocurrent increment at a higher applied potential. Interestingly, the Zr4+-doped hematite photoanode exhibited an onset potential that is similar to those of the pristine and Si4+-doped hematite, but a larger photocurrent density that is similar to those of the Sn4+- and Ti4+-doped photoanodes was recorded. The photoactivity of the doped photoanodes at 1.23 V-RHE follows the order Zr > Sn > Ti > Si. The onset-potential shifts of the doped photoanodes were investigated using the Ab initio calculations that are well correlated with the experimental data. X-ray diffraction (XRD) and scanning-electron microscopy (FESEM) revealed that both the crystalline phase of the hematite and the nanorod morphology were preserved after the doping procedure. X-ray photoelectron spectroscopy (XPS) confirmed the presence of the tetravalent dopants on the hematite nanostructure. The charge-transfer resistance at the various interfaces of the doped photoanodes was studied using impedance spectroscopy. The doping on the hematite photoanodes was confirmed using the Mott-Schottky (MS) analysis. 

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 427, p. 1203-1212
Keywords [en]
Hematite, Akaganeite, Sintering, Nanorods, Onset potential
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-152142DOI: 10.1016/j.apsusc.2017.09.042ISI: 000415219100149OAI: oai:DiVA.org:umu-152142DiVA, id: diva2:1252358
Available from: 2018-10-01 Created: 2018-10-01 Last updated: 2018-10-01Bibliographically approved

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Gracia-Espino, EduardoAnnamalai, Alagappan

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