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Low‐Temperature Activation of Hematite Nanowires for Photoelectrochemical Water Oxidation
Author(s) -
Ling Yichuan,
Wang Gongming,
Wang Hanyu,
Yang Yi,
Li Yat
Publication year - 2014
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201301013
Subject(s) - hematite , photocurrent , nanowire , annealing (glass) , materials science , chemical engineering , water splitting , magnetite , nanostructure , nanotechnology , inorganic chemistry , photocatalysis , chemistry , catalysis , metallurgy , optoelectronics , biochemistry , engineering
Hematite (α‐Fe 2 O 3 ) nanostructures have been extensively studied as photoanode materials for photoelectrochemical (PEC) water oxidation. However, the photoactivity of pristine hematite nanostructures is fairly low and typically requires thermal activation at temperature of 650 °C or above. Here, we report a new method for enhancing the photocurrent of hematite nanowires at a substantially lower temperature of 350 °C by means of a two‐step annealing process (activation process). Hydrothermally grown β‐FeOOH nanowires were first annealed in a pure N 2 environment at 350 °C to form magnetite, followed by partial oxidation in air to convert magnetite to hematite. During this process, Fe 2+ sites (oxygen vacancies) were intentionally created to increase the donor density and therefore the electrical conductivity of hematite. The oxygen‐deficient hematite nanowire photoanode created at low temperature (350 °C) show considerably enhanced photoactivity compared to pristine hematite sample that prepared by thermal annealing of β‐FeOOH nanowires at 550 °C in air. Moreover, this low‐temperature annealing method can be coupled with an element doping method to further increase the photoactivity of hematite nanowire. Sn‐doped hematite nanowires prepared by the same low‐temperature annealing method show at least three fold enhanced photocurrent compared to the undoped sample. Significantly, the highest temperature in the entire annealing process was 350 °C, which is the lowest activation temperature ever reported for hematite nanowire photoanodes.