TY - JOUR
T1 - Kinetics of light-driven oxygen evolution at nanostructured hematite semiconductor electrodes
AU - Schrebler, Ricardo
AU - Ballesteros, Luis A.
AU - Gómez, Humberto
AU - Grez, Paula
AU - Córdova, Ricardo
AU - Muñoz, Eduardo
AU - Schrebler, Rodrigo
AU - Sessarego, Gustavo
AU - Martín, Francisco
AU - Ramos-Barrado, José R.
AU - Dalchiele, Enrique A.
N1 - Funding Information:
This work was supported by Fondecyt Project No. 1120776 and FONDEQUIP Project EQM-0003/2012, Chile. CSIC (Comisi?n Sectorial de Investigaci?n Cient?fica), Universidad de la Rep?blica, in Montevideo, Uruguay, PEDECIBA - F?sica and ANII (Agencia Nacional de Investigaci?n e Innovaci?n) are also acknowledged. The Authors are grateful to Ministry of Economy and Competitiveness with the research project TEC 2014-53906-R and to Junta de Andalucia through the project RNM1399.
Publisher Copyright:
Copyright © 2017 American Scientific Publishers All rights reserved.
PY - 2017
Y1 - 2017
N2 - Hematite nanostructures have been electrochemically grown by ultrasound-assisted anodization of iron substrates in an ethylene glycol based medium. This hematite nano-architecture has been tuned from a 1-D nanoporous layer (grown onto a bare iron foil substrate) to a high aspect self-organized nanotube one (grown onto a pretreated iron foil). Well-developed hematite nanotube arrays perpendicular to the substrate with a 1 μm in length have been obtained. The nanoporous sample was characterized by pores of a mean diameter of 30 nm and an interpore distance of 150 nm, whereas the self-organized nanotube layer consisted of nanotube arrays with a single tube inner diameter of approximately 50 nm and average spacing of approximately 90 nm. The wall thickness of the hematite nanotubes was of approximately 30 nm. A comparative study of the photoelectrochemical properties of these two different hematite nanostructures under water-splitting conditions have been studied through EIS and PEIS methods. The strong correlation between the CSS increase with the RSS,ct decrease and the photocurrent development as the potential is made more anodic, indicated that holes transfer for the water splitting reaction takes place through the surface states and not directly from valence band holes. From the PEIS spectra the rate constants of the elementary reactions responsible for the competing processes of interfacial charge transfer (ktr) and electron-hole recombination (krec) have been determined. A better photoresponse kinetic was observed from the hematite nanotubular structure as compared to the nanoporous one. The last indicates that in the hematite nanotubular structure it exists a very well length scale matching between the nanotube wall thickness and the hole diffusion length (maximize light absorption while maintaining the bulk within hole collection length), diminishing then the recombination processes.
AB - Hematite nanostructures have been electrochemically grown by ultrasound-assisted anodization of iron substrates in an ethylene glycol based medium. This hematite nano-architecture has been tuned from a 1-D nanoporous layer (grown onto a bare iron foil substrate) to a high aspect self-organized nanotube one (grown onto a pretreated iron foil). Well-developed hematite nanotube arrays perpendicular to the substrate with a 1 μm in length have been obtained. The nanoporous sample was characterized by pores of a mean diameter of 30 nm and an interpore distance of 150 nm, whereas the self-organized nanotube layer consisted of nanotube arrays with a single tube inner diameter of approximately 50 nm and average spacing of approximately 90 nm. The wall thickness of the hematite nanotubes was of approximately 30 nm. A comparative study of the photoelectrochemical properties of these two different hematite nanostructures under water-splitting conditions have been studied through EIS and PEIS methods. The strong correlation between the CSS increase with the RSS,ct decrease and the photocurrent development as the potential is made more anodic, indicated that holes transfer for the water splitting reaction takes place through the surface states and not directly from valence band holes. From the PEIS spectra the rate constants of the elementary reactions responsible for the competing processes of interfacial charge transfer (ktr) and electron-hole recombination (krec) have been determined. A better photoresponse kinetic was observed from the hematite nanotubular structure as compared to the nanoporous one. The last indicates that in the hematite nanotubular structure it exists a very well length scale matching between the nanotube wall thickness and the hole diffusion length (maximize light absorption while maintaining the bulk within hole collection length), diminishing then the recombination processes.
KW - EIS
KW - Hematite
KW - Impedance
KW - Nanostructures
KW - Nanotubes
KW - PEIS
KW - Ultrasound-assisted anodization
KW - Water splitting
UR - http://www.scopus.com/inward/record.url?scp=85018242774&partnerID=8YFLogxK
U2 - 10.1166/jnn.2017.14193
DO - 10.1166/jnn.2017.14193
M3 - Article
AN - SCOPUS:85018242774
VL - 17
SP - 4511
EP - 4519
JO - Journal of Nanoscience and Nanotechnology
JF - Journal of Nanoscience and Nanotechnology
SN - 1533-4880
IS - 7
ER -