All-Oxide α‑Fe2O3/H:TiO2 Heterojunction Photoanode: A Platform for Stable and Enhanced Photoelectrochemical Performance through Favorable Band Edge Alignment

To improve the photoelectrochemical (PEC) performance of hematite thin-film photoanode, we report a novel heterostructure based on Fe2O3/TiO2 and hydrogenated Fe2O3/TiO2 (Fe2O3/H:TiO2) for faster charge transfer owing to passivation of surface states in Fe2O3 via TiO2 overlayer and favorable band al...

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Published in:Journal of physical chemistry. C 2019-02, Vol.123 (6), p.3326-3335
Main Authors: Kodan, Nisha, Agarwal, Khushboo, Mehta, B. R
Format: Article
Language:English
Online Access:Get full text
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Summary:To improve the photoelectrochemical (PEC) performance of hematite thin-film photoanode, we report a novel heterostructure based on Fe2O3/TiO2 and hydrogenated Fe2O3/TiO2 (Fe2O3/H:TiO2) for faster charge transfer owing to passivation of surface states in Fe2O3 via TiO2 overlayer and favorable band alignment using hydrogen annealing of TiO2 overlayer. The valence band offset, band gap and work function values have been measured using X-ray photoelectron spectroscopy, optical absorption, and Kelvin probe force microscopy to construct the energy band diagram of the heterostructure photoanodes. The results confirm the upshift in the valence band edge of TiO2 over Fe2O3 after hydrogen treatment of TiO2 overlayer, which leads to the formation of type II band edge alignment in Fe2O3/H:TiO2 heterojunction and improved PEC performance compared to Fe2O3/TiO2, pristine Fe2O3 and TiO2 thin-film photoelectrodes. The well-straddled and improved band alignment in Fe2O3/H:TiO2 heterostructure gives rise to substantial enhancement in photocurrent density, up to 3.36 mA/cm2 at 1.23 V (vs reversible hydrogen electrode (RHE)) with a low onset potential of 0.1 V (vs RHE), under AM1.5 illumination condition. The observed photocurrent density in Fe2O3/H:TiO2 heterostructure is 15-fold higher than bare Fe2O3 (0.22 mA/cm2) photoanode. This work shows how a simple bilayer junction and its hydrogen treatment can be used to enhance the PEC response of heterojunctions and offers valuable insights into the further development of all-oxide heterojunctions.
ISSN:1932-7447
1932-7455
DOI:10.1021/acs.jpcc.8b10794