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Enhanced Charge Separation through ALD‐Modified Fe 2 O 3 /Fe 2 TiO 5 Nanorod Heterojunction for Photoelectrochemical Water Oxidation
Author(s) -
Li Chengcheng,
Wang Tuo,
Luo Zhibin,
Liu Shanshan,
Gong Jinlong
Publication year - 2016
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201600940
Subject(s) - photocurrent , materials science , heterojunction , overlayer , water splitting , reversible hydrogen electrode , nanorod , atomic layer deposition , electrode , photocatalysis , chemical engineering , photoelectrochemistry , analytical chemistry (journal) , nanotechnology , optoelectronics , electrochemistry , layer (electronics) , catalysis , working electrode , chemistry , biochemistry , chromatography , engineering
Hematite suffers from poor charge transport and separation properties for solar water splitting. This paper describes the design and fabrication of a 3D Fe 2 O 3 /Fe 2 TiO 5 heterojunction photoanode with improved charge separation, via a facile hydrothermal method followed by atomic layer deposition and air annealing. A highly crystallized Fe 2 TiO 5 phase forms with a distinct interface with the underlying Fe 2 O 3 core, where a 4 nm Fe 2 TiO 5 overlayer leads to the best photoelectrochemical performance. The favorable band offset between Fe 2 O 3 and Fe 2 TiO 5 establishes a type‐II heterojunction at the Fe 2 O 3 /Fe 2 TiO 5 interface, which drives electron–hole separation effectively. The Fe 2 O 3 /Fe 2 TiO 5 composite electrode exhibits a dramatically improved photocurrent of 1.63 mA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE) under simulated 1 sun illumination (100 mW cm −2 ), which is 3.5 times that of the bare Fe 2 O 3 electrode. Decorating the Fe 2 O 3 /Fe 2 TiO 5 heterojunction photoanode with earth‐abundant FeNiO x cocatalyst further expedites surface reaction kinetics, leading to an onset potential of 0.8 V versus RHE with a photocurrent of 2.7 mA cm −2 at 1.23 V and 4.6 mA cm −2 at 1.6 V versus RHE. This sandwich photoanode shows an excellent stability for 5 h and achieves an overall Faradaic efficiency of 95% for O 2 generation. This is the best performance ever reported for Fe 2 O 3 /Fe 2 TiO 5 photoanodes.